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<td align=LEFT valign=TOP colspan="2" bgcolor="#0080C0"><b><font face="Arial,Helvetica" color="#FFFFFF"> Eclipse
Corner Article</font></b></td>
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</table>
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<h1> <img src="images/idea.jpg" align=CENTER></h1>
<h1 align="center">Drag and Drop</h1>
<h3 align="center">Adding Drag and Drop to an SWT Application</h3>
<p align="justify"><b>Summary</b><br>
Drag and drop provides a quick and easy mechanism for users to re-order and
transfer data within an application and between applications. This article is
an overview of how to implement Drag and Drop and Clipboard data transfers
within an SWT application.</p>
<p><b>By Veronika Irvine, IBM OTI Labs</b><br>
<span style="font-size:10.0pt">August 25, 2003 (revised November 2, 2005)</span></p>
<div align="center" style="text-align:center">
<hr size="2" width="100%" align="center">
</div>
<h2>Drag and Drop Overview</h2>
<p>Consider the simple example of dragging an item from one table to another
as shown in Figure 1:</p>
<p align="center"><img border="0" src="images/image002.jpg"><br>
Figure 1: Shopping Cart example</p>
<p align="justify">On the right there is a list of items that I can purchase
and on the left is my shopping cart. To buy something, I select it from the
list on the right (I have selected “Truffle Assortment” in Figure 1), drag
it over to my shopping cart and drop it. When I let go of the mouse over my
shopping cart, the item will be added to the list of items I wish to purchase.
In this data transfer, the list of assorted chocolates on the right is the
drag source and my shopping cart is the drop target. A drag source is the
source of the data being transferred and a drop target is the receiver. As I
drag the mouse over a drop target, I get feedback in various forms. First, the
cursor changes to let me know that I am over a valid drop target by changing
from a “do not enter” sign to an arrow (this is called a “drag over
effect”). The cursor also tells me what kind of operation will be performed
when the data is transferred – the data may be copied or moved or a link may
be made to the data. Secondly, if I am dragging over a widget that has
sub-items like a tree or table, the sub-item may be highlighted to indicate
that the data will be dropped on a specific sub-item (this is called a “drag
under effect”). This is useful when you are organizing data into folders or
rearranging items. In this article, I will explain in more detail the terms I
have introduced above and how SWT allows an application to define and
manipulate these components.</p>
<ul>
<li><a href="#_Drag_Source">DragSource</a></li>
<li><a href="#_Drop_Target">DropTarget</a></li>
<li><a href="#_Using_the_Clipboard">Clipboard</a></li>
<li><a href="#_Transfer">Transfer</a></li>
</ul>
<h2><a name="_Drag_Source"></a>Drag Source</h2>
<p align="justify">A drag source is the provider of data in a Drag and Drop
data transfer as well as the originator of the Drag and Drop operation. The
data provided by the drag source may be transferred to another location in the
same widget, to a different widget within the same application, or to a
different application altogether. For example, you can drag text from your
application and drop it on an email application, or you could drag an item in
a tree and drop it below a different node in the same tree.</p>
<p align="justify">Let us walk through a simple example showing how to define
a drag source. The example in Listing 1 shows how to drag text from a label
widget.</p>
<table border="1" cellspacing="0" cellpadding="0" style="width:650">
<tr>
<td width="43" valign="top" style="width:.45in;border-top:solid windowtext .5pt;
border-left:solid windowtext .5pt;border-bottom:none;border-right:none;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds1C" href="#_ds1D">1</a></td>
<td valign="top" style="width:788;border-top:.5pt solid windowtext;
border-left:medium none;border-bottom:medium none;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>import
org.eclipse.swt.dnd.*;</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">2</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds4C" href="#_ds4D">3</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">//
Enable a label as a Drag Source</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds4D">4</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>final
Label dragLabel = new Label(shell, SWT.BORDER);</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds4D">5</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>dragLabel.setText("text
to be transferred");</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">6</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds8C" href="#_ds8D">7</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">//
Allow data to be copied or moved from the drag source</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds8D">8</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>int
operations = DND.DROP_MOVE | DND.DROP_COPY;</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds8D">9</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>DragSource
source = new DragSource(dragLabel, operations);</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">10</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds12C" href="#_ds12D">11</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">//
Provide data in Text format</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds12D">12</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>Transfer[]
types = new Transfer[] {TextTransfer.getInstance()};</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds12D">13</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>source.setTransfer(types);</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">14</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds15C" href="#_ds15D">15</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>source.addDragListener(new
DragSourceListener() {</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds16C" href="#_ds16D">16</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragStart(DragSourceEvent event) {</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds16D">17</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
<font color="#0080C0">// Only start the drag if there is actually text
in the</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds16D">18</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
<font color="#0080C0">// label - this text will be what is dropped on the target.</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds16D">19</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> if
(dragLabel.getText().length() == 0) {</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds16D">20</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> event.doit
= false;</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds16D">21</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> }</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds16D">22</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds23C" href="#_ds23D">23</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragSetData(DragSourceEvent event) {</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds23D">24</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">
// Provide the data of the requested type.</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds23D">25</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> if
(TextTransfer.getInstance().isSupportedType(event.dataType)) {</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds23D">26</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> event.data
= dragLabel.getText();</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds23D">27</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> }</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds23D">28</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_ds29C" href="#_ds29D">29</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragFinished(DragSourceEvent event) {</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds29D">30</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> <font color="#0080C0">//
If a move operation has been performed, remove the data</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds29D">31</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> <font color="#0080C0">//
from the source</font></code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds29D">32</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> if
(event.detail == DND.DROP_MOVE)</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds29D">33</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code> dragLabel.setText("");</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_ds29D">34</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">35</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:788;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="43" valign="top" style="width:.45in;border-top:none;border-left:solid windowtext .5pt;
border-bottom:solid windowtext .5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt">36</td>
<td valign="top" style="width:788;border-top:medium none;border-left:medium none;
border-bottom:.5pt solid windowtext;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>});</code></td>
</tr>
</table>
<p align="left">Listing 1: Dragging text from a Label widget.
<p align="justify"><a name="_ds1D" href="#_ds1C"><b>Line 1:</b></a><br>
All the SWT drag and drop classes are defined in the package
org.eclipse.swt.dnd.</p>
<p align="justify"><a name="_ds4D" href="#_ds4C"><b>Lines 3 to 5:</b></a><br>
Create a widget. In order to start a drag, the user holds the mouse button
down in a widget and drags the mouse. In our example, the user starts the drag
in the label. Note that you cannot have multiple drag sources on one widget.
If you try to create a second drag source, an SWTError will be thrown.</p>
<p align="justify"><a name="_ds8D" href="#_ds8C"><b>Lines 7 to 9:</b></a><br>
To make a widget into a drag source, we must create an
org.eclipse.swt.dnd.DragSource object. The DragSource constructor takes two
arguments, the widget that will be the location of the drag source and the
operations that are allowed. The allowed operations determine what kind of
actions the drop target can do with the data being transferred. The allowed
values are any bitwise OR combination of DND.DROP_COPY, DND.DROP_MOVE or
DND.DROP_LINK. In the example, we are allowing the data to be copied or moved.</p>
<p align="justify"><a name="_ds12D" href="#_ds12C"><b>Lines 11 to 13:</b></a><br>
To complete the definition of a drag source, you must specify the types of
data that can be transferred. A data type is defined by a subclass
org.eclipse.swt.dnd.Transfer such as TextTransfer or FileTransfer. For a
detailed description of Transfer types see <a href="#_Transfer">Transfer</a>.
A drag source can provide more than one format of the data, however, it is
required to provide the data in any of the specified formats when requested.
In this example, the user can drag text from the label.</p>
<p align="justify"><a name="_ds15D" href="#_ds15C"><b>Line 15:</b></a><br>
Once the drag source is defined, a mechanism is required for it to interact
with the Drag and Drop operation. Adding a DragSourceListener does this.</p>
<p align="justify">The following event sequences may occur:</p>
<ol>
<li>dragStart</li>
<li>dragStart, one or more dragSetData, dragFinished</li>
<li>dragStart, dragFinished</li>
</ol>
<p align="justify"><a name="_ds16D" href="#_ds16C"><b>Lines 16 to 22:</b></a><br>
The dragStart event signals that the user has performed the action that
initiates a Drag and Drop operation. The exact action taken by the user
depends on the platform – on Windows for example, the user presses down with
the left mouse button and drags for a certain number of pixels (the exact
distance is configurable by the user in the Mouse control panel). On Motif,
the user presses down the middle mouse button. The application does not need
to be concerned about the exact conditions that started the operation because
SWT handles these platform differences. When the dragStart event is received,
the application has the choice to start a Drag and Drop operation or not. For
example, if no valid items are currently selected in the drag source widget,
the application may choose to cancel the operation. The operation is cancelled
by setting the event.doit field to ‘false’.</p>
<p align="justify">Note: the application is not required to specify the type
of data that will be transferred until the dragStart event has been received.
That is, the application can defer the call to DragSource.setTransfer until
the dragStart event. However, once the dragStart event has been processed, if
no transfer types have been specified for the drag source, the Drag and Drop
operation will be cancelled.</p>
<p align="justify">By allowing the Drag and Drop operation, the application is
making a promise to provide data of the specified type when requested. Failure
to do so is a violation of the DND contract and could result in unexpected
behavior.</p>
<p align="justify"><a name="_ds23D" href="#_ds23C"><b>Lines 23 to 28:</b></a><br>
The dragSetData event is a request for the data promised in the dragStart
event. This event may be called multiple times either repeatedly for the same
data type or for any of the data types promised. On some platforms, a
potential drop target can request data when the mouse is moving over the drop
target (e.g. Windows) and on some platforms the data may only be requested
when a drop is performed (the mouse is released over a valid drop site) (e.g.
Motif). Therefore, do not make any assumptions that the drag and drop
operation is completed when receiving this event. There is no way to know
where the data is being dropped – it could be dropped on the same
application, even on the same widget or on another application.</p>
<p align="justify">The type of data being requested is specified in the
event.dataType field. The event.dataType field contains a TransferData object.
While the fields of the TransferData object are public, they are platform
dependant. Therefore, you should not access the fields directly but rather
pass the TransferData to a Transfer object to determine the type of data. This
is done in the example by calling TextTransfer.getInstance().isSupportedType
(line 25).</p>
<p align="justify">The drag source must fill in the event.data field. The
exact form of the data depends on the Transfer type. For example, TextTransfer
expects a String object containing the entire text whereas a FileTransfer
expects a String array where each entry in the array is the absolute path of a
File. The javadoc for each transfer type should describe the expected value
for the Java object being transferred. More information on Transfer and
TransferData is available in the <a href="#_Transfer">Transfer</a> section of
this document.</p>
<p align="justify"><a name="_ds29D" href="#_ds29C"><b>Lines 29 to 34:</b></a><br>
The dragFinished event indicates that the drag and drop operation is complete.
The user may have dropped the data on a valid location, dropped the data on an
invalid location or hit Escape. If the user dropped the data on an invalid
location or hit Escape, the event.doit field will be false and the
event.detail field will be DND.DROP_NONE. If the user dropped the data on a
valid location, the event.doit field will be true and the event.detail field
will indicate the kind of operation performed by the drop target. This will be
one of values specified in table 1.</p>
<table border="1" cellspacing="0" cellpadding="2" width="90%">
<tr>
<th width="30%" valign="top" height="19">dragFinished event.detail value</th>
<th width="70%" valign="top" height="19">Description</th>
</tr>
<tr>
<td width="30%" valign="top" height="19">DND.DROP_COPY</td>
<td width="70%" valign="top" height="19">The drop target made a copy of
the data.</td>
</tr>
<tr>
<td width="30%" valign="top" height="20">DND.DROP_LINK</td>
<td width="70%" valign="top" height="20">The drop target made a link to
the data – usually only used for files.</td>
</tr>
<tr>
<td width="30%" valign="top" height="38">DND.DROP_MOVE</td>
<td width="70%" valign="top" height="38">The drop target made a copy of
the data and the drag source should now delete the original and update
its display.</td>
</tr>
<tr>
<td width="30%" valign="top" height="57">DND.DROP_TARGET_MOVE</td>
<td width="70%" valign="top" height="57">The drop target moved the data
from its original location to a new location. This is usually only used
with files. In this case, the drag source does not need to delete the
original; it just needs to update its display information.</td>
</tr>
</table>
<p align="left">Table 1: Valid dragFinished event.detail values
<h2><a name="_Drop_Target"></a>Drop Target</h2>
<p align="justify">A drop target receives data in a Drag and Drop operation.
The data received by the drop target may have come from the same widget, from
a different widget within the same application, or from a different
application altogether. For example, you can drag text from an email
application and drop it on your application, or you could drag an item in a
tree and drop it below a different node in the same tree.</p>
<p align="justify">Let us walk through a simple example showing how to define
a drop target. The example in Listing 2 shows how to drop files or text on a
table widget.</p>
<table border="1" cellspacing="0" cellpadding="0" style="width:680;
border-collapse:collapse;border:medium none;">
<tr>
<td width="31" valign="top" style="width:23.4pt;border-top:solid windowtext .5pt;
border-left:solid windowtext .5pt;border-bottom:none;border-right:none;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt1C" href="#_dt1D">1</a></td>
<td valign="top" style="width:1060;border-top:.5pt solid windowtext;
border-left:medium none;border-bottom:medium none;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>import
org.eclipse.swt.dnd.*;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">2</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"> </td>
<code></code>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt3C" href="#_dt3D">3</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">//
Enable a table as a Drop Target</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt3D">4</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>final
Table dropTable = new Table(shell, SWT.BORDER);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt3D">5</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>for
(int i = 0; i < 10; i++) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt3D">6</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
TableItem item = new TableItem(dropTable, SWT.NONE);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt3D">7</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
item.setText("item" + I);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt3D">8</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">9</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt10C" href="#_dt10D">10</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">//
Allow data to be copied or moved to the drop target</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt10D">11</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>operations
= DND.DROP_MOVE | DND.DROP_COPY | DND.DROP_DEFAULT;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt10D">12</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>DropTarget
target = new DropTarget(dropTable, operations);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">13</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt14C" href="#_dt14D">14</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">//
Receive data in Text or File format</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt14D">15</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>final
TextTransfer textTransfer = TextTransfer.getInstance();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt14D">16</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>final
FileTransfer fileTransfer = FileTransfer.getInstance();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt14D">17</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>types
= new Transfer[] {fileTransfer, textTransfer};</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt14D">18</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>target.setTransfer(types);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">19</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code></code> </td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt20C" href="#_dt20D">20</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>target.addDropListener(new
DropTargetListener() {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt21C" href="#_dt21D">21</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragEnter(DropTargetEvent event) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt22C" href="#_dt22D">22</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if (event.detail == DND.DROP_DEFAULT) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt22D">23</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if ((event.operations & DND.DROP_COPY) != 0) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt22D">24</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail = DND.DROP_COPY;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt22D">25</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
} else {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt22D">26</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail = DND.DROP_NONE;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt22D">27</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt22D">28</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt29C" href="#_dt29D">29</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code><font color="#0080C0">
// will accept text but prefer to have files dropped</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">30</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
for (int i = 0; i < event.dataTypes.length; i++) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">31</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if (fileTransfer.isSupportedType(event.dataTypes[i])){</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">32</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.currentDataType = event.dataTypes[i];</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">33</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
<font color="#0080C0">// files should only be copied</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">34</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if (event.detail != DND.DROP_COPY) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">35</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail = DND.DROP_NONE;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">36</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">37</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
break;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">38</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt29D">39</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">40</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt41C" href="#_dt41D">41</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragOver(DropTargetEvent event) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt42C" href="#_dt42D">42</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.feedback = DND.FEEDBACK_SELECT | DND.FEEDBACK_SCROLL;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt43C" href="#_dt43D">43</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if
(textTransfer.isSupportedType(event.currentDataType)) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt43D">44</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
<font color="#0080C0">// NOTE: on unsupported platforms this will return null</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt43D">45</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
Object o = textTransfer.nativeToJava(event.currentDataType);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt43D">46</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
String t = (String)o;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt43D">47</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if (t != null) System.out.println(t);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt43D">48</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">50</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt51C" href="#_dt51D">51</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragOperationChanged(DropTargetEvent event) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">52</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if (event.detail == DND.DROP_DEFAULT) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">53</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail = (event.operations & DND.DROP_COPY) != 0) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">54</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail = DND.DROP_COPY;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">55</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
} else {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">56</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail = DND.DROP_NONE;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">57</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">58</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">59</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
<font color="#0080C0">// allow text to be moved
but files should only be copied</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">60</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if
(fileTransfer.isSupportedType(event.currentDataType)){</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">61</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if (event.detail !=
DND.DROP_COPY) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">62</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
event.detail
= DND.DROP_NONE;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">63</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">64</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt51D">65</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt66C" href="#_dt66D">66</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dragLeave(DropTargetEvent event) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt66D">67</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt68C" href="#_dt68D">68</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void dropAccept(DropTargetEvent event) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt68D">69</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_dt70C" href="#_dt70D">70</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
public void drop(DropTargetEvent event) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">71</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if
(textTransfer.isSupportedType(event.currentDataType)) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">72</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
String text =
(String)event.data;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">73</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
TableItem item = new
TableItem(dropTable, SWT.NONE);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">74</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
item.setText(text);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">75</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">76</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
if
(fileTransfer.isSupportedType(event.currentDataType)){</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">77</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
String[] files =
(String[])event.data;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">78</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
for (int i = 0; i <
files.length; i++) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">79</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
TableItem
item = new TableItem(dropTable, SWT.NONE);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">80</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
item.setText(files[i]);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">81</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">82</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_dt70D">83</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:1060;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border-top:none;border-left:solid windowtext .5pt;
border-bottom:solid windowtext .5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt">84</td>
<td valign="top" style="width:1060;border-top:medium none;border-left:
medium none;border-bottom:.5pt solid windowtext;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>});</code></td>
</tr>
</table>
<p align="left">Listing 2: Drop text or files on a table widget
<p align="justify"><a name="_dt1D" href="#_dt1C"><b>Line 1:</b></a><br>
All the related drag and drop classes are defined in the package
org.eclipse.swt.dnd.</p>
<p align="justify"><a name="_dt3D" href="#_dt3C"><b>Lines 3 to 8:</b></a><br>
Create a widget. The user drags the data over a target, which in user
interface terms is some visible widget. In our example, the user can drop the
data on a table. Note that you cannot have multiple drop targets on one
widget. If you try to create a second drop target, an SWTError will be thrown.</p>
<p align="justify"><a name="_dt10D" href="#_dt10C"><b>Lines 10 to 12:</b></a><br>
Define the types of operations that this drop target is likely to perform on
any data dropped on it. This is a bitwise OR combination of any of
DND.DROP_COPY, DND.DROP_MOVE, or DND.DROP_LINK. By default, if no operations
are defined, the DND.DROP_MOVE operation is assumed.</p>
<p align="justify">The operation may also include DND.DROP_DEFAULT (Note: the
DND.DROP_DEFAULT style must be combined with one or more of the other
DND.DROP_* styles). The DND.DROP_DEFAULT style allows the drop target to
determine the default operation – the default operation is what happens when
no modifier keys are pressed. If the DND.DROP_DEFAULT style is NOT specified,
the default operation will be DND.DROP_MOVE. See also dragEnter and
dragOperationChanged below.</p>
<p align="justify"><a name="_dt14D" href="#_dt14C"><b>Lines 14 to 18:</b></a><br>
Define the types of data that this drop target will accept. A data type is
defined by a subclass org.eclipse.swt.dnd.Transfer such as TextTransfer or
FileTransfer. For a detailed description of Transfer types see <a href="#_Transfer">Transfer</a>.
A drop target can be receptive to more than one type of data. The current 2.1
implementation will, however, only allow one format to be retrieved in the
final drop. That is to say, the drop target can indicate that it is interested
in both text and RTF text, but only one of these is provided in the drop event
– either text or RTF text. The advantage of registering for both formats is
that some applications may only provide text and some may only provide RTF
text. If an application provides both, you can choose which format you would
prefer to receive. See dragEnter below.</p>
<p align="justify"><a name="_dt20D" href="#_dt20C"><b>Line 20:</b></a><br>
Once the drop target is defined, a mechanism is required for it to interact
with the Drag and Drop operation. Adding a DropTargetListener does this.</p>
<p align="justify">The following event sequences may occur:</p>
<ul>
<li>dragEnter, dragLeave</li>
<li>dragEnter, one or more dragOver *, dragLeave</li>
<li>dragEnter, one or more dragOver *, dragLeave, dropAccept</li>
<li>dragEnter, one or more dragOver *, dragLeave, dropAccept, drop</li>
</ul>
<p>*may be a mixture of dragOver and dragOperationChanged</p>
<p align="justify"><a name="_dt21D" href="#_dt21C"><b>Line 21 to 40:</b></a><br>
The dragEnter event occurs when a drag and drop operation is in progress and
the cursor enters the bounds of the drop target widget. If the cursor leaves
the bounds of the widget and re-enters, another dragEnter is issued.</p>
<p align="justify"><a name="_dt22D" href="#_dt22C"><b>Lines 22 to 28:</b></a><br>
A drag over effect is a visual cue to the user about what kind of operation
will be performed when the drop occurs. The exact appearance of the visual cue
is platform dependant – some examples are shown in Figure 2. The drop target
can update this drag over effect by setting the event.detail field to one of
DND.DROP_COPY, DND.DROP_MOVE, DND.DROP_LINK or DND.DROP_NONE. The value set in
the event.detail field must be one of the values defined in the
event.operations field, which is a bitwise OR of the operations supported by
the DragSource. If a value is chosen that is not allowed by the DragSource,
the operation would be set to DND.DROP_NONE. The event.detail field can also
be updated in the dragOver, dragOperationChanged, dropAccept and drop events.</p>
<p align="justify">In dragEnter, the application can define the default
operation. As discussed above, if the drop target is created with the style
DND.DROP_DEFAULT, it will be notified when there are no user modifier keys
pressed. In this case, the event.detail field in the dragEnter event is set to
DND.DROP_DEFAULT. The application can specify the default operation by
changing the event.detail field to the desired operation. If the application
does not change the event.detail field from DND.DROP_DEFAULT to some
operation, it will by default be changed to DND.DROP_MOVE. The
DND.DROP_DEFAULT value is also set in the dragOperationChanged event.</p>
<p align="justify">In our example, we make Copy the default operation if it is
allowed by the drag source.</p>
<table border="1" cellspacing="0" cellpadding="2" style="border-collapse:collapse;
border:none;" width="30%">
<tr>
<th valign="top" width="50%">
<p>Operation</p>
</th>
<th valign="top" width="50%">Win32 cursor</th>
</tr>
<tr>
<td valign="top" width="50%" align="center">Move</td>
<td valign="top" width="50%" align="center"><img border="0" width="21" height="31" src="images/image004.jpg"></td>
</tr>
<tr>
<td valign="top" width="50%" align="center">Copy</td>
<td valign="top" width="50%" align="center"><img border="0" width="26" height="38" src="images/image006.jpg"></td>
</tr>
<tr>
<td valign="top" width="50%" align="center">Link</td>
<td valign="top" width="50%" align="center"><img border="0" width="27" height="38" src="images/image008.jpg"></td>
</tr>
<tr>
<td valign="top" width="50%" align="center">None</td>
<td valign="top" width="50%" align="center"><img border="0" width="22" height="22" src="images/image010.jpg"></td>
</tr>
</table>
<p align="left">Figure 2: Cursors for the allowed transfer operations
<p align="justify"><a name="_dt29D" href="#_dt29C"><b>Lines 29 to 39:</b></a><br>
The drop target can choose what type of data it would prefer to receive. The
dragEnter event has two fields for this, event.currentType, which is the type
of data preferred by the application (represented by a TransferData object),
and event.dataTypes, which is the list of types provided by the drag source
(represented by an array of TransferData objects). You can set the
event.currentType to any value in the event.dataTypes. These fields can also
be modified in the dragOver, dragOperationChanged, and dropAccept events.</p>
<p align="justify">In the example, we are allowing Text or Files to be dropped
on the table, but if both are available, we prefer to get the Files. If a file
is being transferred, we also have restricted the operation to allow only copy
(we don’t want you to delete files from your operating system when you play
with this example :-)).</p>
<p align="justify"><a name="_dt41D" href="#_dt41C"><b>Lines 41 to 50:</b></a><br>
The dragOver event occurs repeatedly as the user drags the cursor over the
drop target widget. If the cursor is motionless, the dragOver event will
continue to be received at regular intervals. In addition to what is shown in
the example, you can modify the event.detail or event.currentType fields. This
is most often done with a table or tree when the operation changes based on
what item you are over. For example, you may have a tree representing the file
system and you may allow files to be dropped on folders but not on other
files. The event.item field will indicate what item you are over in a table or
tree.</p>
<p align="justify"><a name="_dt42D" href="#_dt42C"><b>Line 42:</b></a><br>
A drag under effect is some visual cue or action in the drop target widget
that gives the user more detailed feedback about where the drop may occur. The
application can control the drag under effect by setting the event.feedback
field as shown in Table 2.</p>
<table border="1" cellspacing="0" width="90%" cellpadding="2">
<tr>
<th align="center" valign="top">dragOver event.feedback values</th>
<th align="center" valign="top">Description</th>
</tr>
<tr>
<td height="24" align="left" valign="top">DND.FEEDBACK_SELECT</td>
<td align="left" valign="top">The item under the cursor is selected;
applies to table and trees.</td>
</tr>
<tr>
<td align="left" valign="top">DND.FEEDBACK_SCROLL</td>
<td align="left" valign="top">The widget is scrolled up or down to allow
the user to drop on items that are not currently visible; applies to
tables and trees.</td>
</tr>
<tr>
<td align="left" valign="top">DND.FEEDBACK_EXPAND</td>
<td align="left" valign="top">The item currently under the cursor is
expanded to allow the user to select a drop target from a sub item;
applies to trees.</td>
</tr>
<tr>
<td align="left" valign="top">DND.FEEDBACK_INSERT_BEFORE</td>
<td align="left" valign="top">An insertion mark is shown before the item
under the cursor; applies to trees.</td>
</tr>
<tr>
<td align="left" valign="top">DND.FEEDBACK_INSERT_AFTER</td>
<td align="left" valign="top">An insertion mark is shown after the item
under the cursor; applies to trees.</td>
</tr>
<tr>
<td align="left" valign="top">DND.FEEDBACK_NONE</td>
<td align="left" valign="top">No effect is shown.</td>
</tr>
</table>
<p align="left">Table 2: drag under effect types
<p align="justify"><a name="_dt43D" href="#_dt43C"><b>Lines 43 to 49:</b></a><br>
When dragging data over the target, the information provided in the event
tells you what type of data is being dragged but does not give the content of
the data. For example, the event.currentType may indicate that a file is being
dragged but the event does not indicate the name of the file or the extension
of the file. If your application will perform a different operation for a Java
file versus a text file, then you might want to get the data in the dragOver
event. Unfortunately this is not supported on all platforms. As of 2.1, it is
only possible to access the data in the dragOver event on Windows. The data
can be accessed by passing the event.currentType TransferData object to the
nativeToJava method of the corresponding Transfer object. On all platforms
except Windows, this will return null. In the future, this capability may be
extended to other platforms where supported.</p>
<p align="justify">(Note: in 1.0 through 2.1, you can only get the data for
event.currentType but in 3.0, you can get the data for any type in
event.dataTypes).</p>
<p align="justify"><a name="_dt51D" href="#_dt51C"><b>Lines 51 to 65:</b></a><br>
The dragOperationChanged event occurs when the user presses or releases a
modifier key (such as Ctrl, Shift, Command, Option). The modifier keys are
used to switch the operation to be performed. For example, on Windows when
just the Ctrl key is down, a copy is requested, when the Ctrl and Shift keys
are both down, a link is requested and when just the Shift key is down, a move
is requested. When no modifier keys are pressed, the default operation is
requested. See the dragEnter event for more details.</p>
<p align="justify"><a name="_dt66D" href="#_dt66C"><b>Lines 66 to 67:</b></a><br>
The dragLeave event occurs when the cursor moves outside of the drop target
widget. If you allocated any resources in dragEnter, you should free them in
dragLeave. The dragLeave event also occurs if the user cancels the Drag and
Drop operation by hitting Escape, and just before a drop is performed.</p>
<p align="justify"><a name="_dt68D" href="#_dt68C"><b>Lines 68 to 69:</b></a><br>
The dropAccept event provides the application with one last chance to define
the type of data that will be returned in the drop event. This is done by
setting the event.currentDataType to one of the values defined in
event.dataTypes.</p>
<p align="justify"><a name="_dt70D" href="#_dt70C"><b>Lines 70 to 83:</b></a><br>
The drop event occurs when the user releases the mouse over the drop target if
a valid operation and currentDataType were requested in the previous events.
The event.data field contains the data requested. The object type contained in
the event.data field depends on what Transfer type was requested. The data is
of the type defined in the event.currentDataType field.</p>
<p align="justify">When the drop operation is completed, update the
event.detail field with the operation performed.</p>
<h2><a name="_Using_the_Clipboard"></a>Clipboard</h2>
<p align="justify">Drag and drop allows the simultaneous transfer of data
between a source and a target but sometimes the user may wish to copy data to
be transferred at a later point in time. The Clipboard acts like a temporary
holder for the data. In addition, the same data may be copied to multiple
targets using the clipboard.</p>
<p align="justify">In the following example, we will copy data in two
different formats onto the clipboard and retrieve one of the formats from the
clipboard.</p>
<table border="1" cellspacing="0" cellpadding="0" style="width:650" width="650">
<tr>
<td width="31" valign="top" style="width:23.4pt;border-top:solid windowtext .5pt;
border-left:solid windowtext .5pt;border-bottom:none;border-right:none;
padding:0in 5.4pt 0in 5.4pt"><a name="_cb1C" href="#_cb1D">1</a></td>
<td valign="top" style="width:850;border-top:.5pt solid windowtext;
border-left:medium none;border-bottom:medium none;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in"><code>import
org.eclipse.swt.dnd.*;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">2</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code>. . .</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">3</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code>public static void main(String[] args) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">4</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> Display display = new Display();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_cb5C" href="#_cb5D">5</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> final Clipboard cb = new Clipboard(display);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">6</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> Shell shell = new Shell(display);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">7</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> final Text text = new Text(shell, SWT.BORDER | SWT.MULTI);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">8</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> text.setBounds(10, 10, 300, 300);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">9</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> Button button = new Button(shell, SWT.PUSH);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">10</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button.setText("Copy");</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">11</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button.setBounds(320, 10, 100, 40);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">12</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button.addListener(SWT.Selection, new Listener() {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">13</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> public void handleEvent(Event e) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_cb14C" href="#_cb14D">14</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> String textData = text.getSelectionText();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">15</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> if (textData == null) return;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">16</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> <font color="#0080C0">// to show the rtf formatting, make the text bold and italic</font></code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">17</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> String rtfData = "{\\rtf1\\b\\i " + textData + "}";</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">18</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> TextTransfer textTransfer = TextTransfer.getInstance();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">19</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> RTFTransfer rtfTransfer = RTFTransfer.getInstance();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">20</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> Transfer[] types = new Transfer[]{textTransfer, rtfTransfer};</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb14D">21</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> cb.setContents(new Object[]{textData, rtfData}, types);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">22</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> }</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">23</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> });</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">24</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button = new Button(shell, SWT.PUSH);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">25</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button.setText("Paste");</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">26</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button.setBounds(320, 60, 100, 40);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">27</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> button.addListener(SWT.Selection, new Listener() {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">28</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> public void handleEvent(Event e) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_cb29C" href="#_cb29D">29</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> TextTransfer transfer = TextTransfer.getInstance();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb29D">30</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> String data = (String)cb.getContents(transfer);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb29D">31</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> if (data == null) return;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a href="#_cb29D">32</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> text.insert(data);</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">33</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> }</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">34</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> });</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">35</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> shell.open();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">36</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> while (!shell.isDisposed()) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">37</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> if (!display.readAndDispatch())</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">38</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> display.sleep();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">39</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code></code> </td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">40</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> }</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt"><a name="_cb41C" href="#_cb41D">41</a></td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> cb.dispose();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border:none;border-left:solid windowtext .5pt;
padding:0in 5.4pt 0in 5.4pt">42</td>
<td valign="top" style="border-left:medium none; border-top:medium none; border-bottom:medium none; width:850;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code> display.dispose();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width:23.4pt;border-top:none;border-left:solid windowtext .5pt;
border-bottom:solid windowtext .5pt;border-right:none;padding:0in 5.4pt 0in 5.4pt">43</td>
<td valign="top" style="width:850;border-top:medium none;border-left:medium none;
border-bottom:.5pt solid windowtext;border-right:.5pt solid windowtext;
padding-left:5.4pt; padding-right:5.4pt; padding-top:0in; padding-bottom:0in">
<code>}</code></td>
</tr>
</table>
<p align="left">Listing 3: Using the clipboard to copy text
<p align="justify"><a name="_cb1D" href="#_cb1C"><b>Line 1:</b></a><br>
All the related drag and drop classes are defined in the package
org.eclipse.swt.dnd.</p>
<p align="justify"><a name="_cb5D" href="#_cb5C"><b>Line 5:</b></a><br>
Create a clipboard object. A Clipboard object gives you access to the
operating system clipboard. It will allow you to exchange data within your
application or with other applications. Note: A Clipboard object uses system
resources and must be released when you are finished (see line 41). You can
choose to create a new clipboard object each time you want to access the data
on the clipboard or you can keep an instance around for your application.</p>
<p align="justify"><a name="_cb14D" href="#_cb14C"><b>Lines 14 to 21:</b></a><br>
Copy the text selected in the Text widget onto the clipboard. If no text is
selected, do nothing.</p>
<p>When placing data on the clipboard, it is possible to make the data
available in more than one format. In our example, we are using both Text and
RTF Text formats. This makes it possible for our application to interact with
a larger variety of applications. That is, if we only place RTF text on the
clipboard, then we cannot interact with an application such as Notepad that
does not understand RTF text. To better integrate your application into the
environment, make your data available in as many useful forms as possible.</p>
<p>Each successful call to Clipboard.setContents will clear any previous
content from the clipboard. This applies not only to the data formats you are
placing on the clipboard but to all data formats. For example, if the
clipboard contains File data placed there by some other application and you
call Clipboard.setContents with Text data, the File data will no longer be
available. If you want to have multiple kinds of data available on the
clipboard at the same time, you must pass them to the clipboard in the same
Clipboard.setContents call. The Clipboard.setContents API takes an array of
data objects and an array of data types. The values for the data objects must
be in the same order as the data types and must be valid for the corresponding
data type (that is, a TextTransfer expects a String, a File Transfer expects a
String[] - the javadoc for each type should specify the expected format of the
data).</p>
<p>The data that you place on the clipboard will be available even after your
application is closed. (Note: GTK is an exception to this. Currently, there is
no mechanism in GTK to persist the data beyond the life time of the
application.)</p>
<p>On some platforms, there are actually multiple clipboards available. On
Unix/Linux there is a PRIMARY clipboard which is supposed to contain the data
that was most recently selected (implicitly set by the act of selection) and
there is a CLIPBOARD clipboard which is supposed to contain data that was
explicitly set through a keyboard accelerator (such as CTRL+Insert) or through
a menu item (there are also other clipboards but these are used infrequently).
On GTK and Motif, you can use <code>DND.CLIPBOARD</code> and
<code>DND.SELECTION_CLIPBOARD</code> when setting and getting clipboard data
to target a specific one. On Mac OS X, SWT supports the default Scrap.</p>
<p><a name="_cb29D" href="#_cb29C"><b>Lines 29 to 32:</b></a><br>
If there is Text available on the clipboard, insert it into the text widget.</p>
<p>To request data of a certain type, call Clipboard.getContents with a
Transfer subclass of the appropriate type. In our example, we are pasting Text
and have used the TextTransfer class. If there is no data of this type
available, null will be returned. The type of object returned by
Clipboard.getContents will depend on the Transfer class used. The javadoc for
the Transfer subclass should specify the Java object type.</p>
<p><a name="_cb41D" href="#_cb41C"><b>Line 41:</b></a><br>
Dispose of the clipboard. As mentioned above, failure to dispose the clipboard
will result in system resources being leaked.</p>
<h3>NEW for 3.0 – How to query data types on the Clipboard</h3>
<p>In 2.1 and earlier releases of SWT, the only mechanism available to
determine if a specific data type is available on the clipboard is to use
Clipboard.getContents and actually transfer the data. In addition to being
slow, this mechanism can cause problems when a "Cut" operation is
being performed. In a "Cut" operation, one application puts data on
the clipboard and when that data is transferred from the clipboard, the
original copy of the data is deleted. In 3.0, there will be new API to query
what types of data are on the clipboard without actually transferring the data
to your application. An example of how to use it is shown in Listing 4.</p>
<table border="1" cellpadding="0" cellspacing="0" width="650">
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">1</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>TransferData[]
available = cb.getAvailableTypes();</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">2</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>boolean
enabled = false;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">3</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>for
(int i = 0; i < available.length; i++) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">4</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>
if (TextTransfer.getInstance().isSupportedType(available[i])) {</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">5</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>
enabled = true;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">6</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>
break;</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">7</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>
}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt none windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17">8</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="17"><code>}</code></td>
</tr>
<tr>
<td width="31" valign="top" style="width: 23.4pt; border-left: .5pt solid windowtext; border-right-style: none; border-right-width: medium; border-top-style: none; border-top-width: medium; border-bottom: .5pt solid windowtext; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="18">9</td>
<td valign="top" style="width: 658; border-left-style: none; border-left-width: medium; border-right: .5pt solid windowtext; border-top-style: none; border-top-width: medium; border-bottom-style: none; border-bottom-width: medium; padding-left: 5.4pt; padding-right: 5.4pt; padding-top: 0in; padding-bottom: 0in" height="18"><code>pasteMenuItem.setEnabled(enabled);</code></td>
</tr>
</table>
<p align="left">Listing 4: Query the data types available on the clipboard.
<p>Clipboard.getAvailableTypes returns an array of TransferData objects. A
TransferData object contains platform specific information that represents a
data type. While the fields of the TransferData object are public, do not
attempt to interpret them directly. Instead use the
"isSupportedType" method of any subclass of Transfer as shown in
line 4.</p>
<h2><a name="_Transfer"></a>Transfer</h2>
<p>Transfer is an abstract class that provides a mechanism for converting
between a Java representation of data and a platform specific representation
of data and vice versa. The Java representation of the data is the currency
the application uses. For example, text is represented by a String object. The
platform specific representation is the currency of the operating system and
is represented in SWT by the TransferData object. Table 3 shows the subclasses
of Transfer provided in org.eclipse.swt.dnd.</p>
<table border="1" cellpadding="2" cellspacing="0" width="90%">
<tr>
<th width="15%" align="center">Transfer</th>
<th width="20%" align="center">Java format</th>
<th width="60%" align="center">Example</th>
</tr>
<tr>
<td width="15%"><code>TextTransfer</code></td>
<td width="20%"><code>String</code></td>
<td width="60%"><code>"hello world"</code></td>
</tr>
<tr>
<td width="15%"><code>RTFTransfer</code></td>
<td width="20%"><code>String</code></td>
<td width="60%"><code>"{\\rtf1\\b\\i hello world}"</code></td>
</tr>
<tr>
<td width="15%"><code>FileTransfer</code></td>
<td width="20%"><code>String[]</code></td>
<td width="60%"><code>new String[] {file1.getAbsolutePath(),
file2.getAbsolutePath()}</code></td>
</tr>
</table>
<p align="left">Table 3: Transfer types provided by SWT
<p>The TransferData class contains public fields that are platform-specific.
Because the fields in TransferData vary from platform to platform,
applications should not access them. The purpose of making the fields public
is to allow developers to extend the Transfer class and provide additional
platform specific types for data transfer (e.g., bitmap images or wave files).</p>
<h2>Summary</h2>
<p>This article describes the SWT mechanism for transferring data either via
Drag and Drop or using the Clipboard. SWT uses the underlying operating system
mechanism which allows data transfer across applications for maximum system
integration. SWT provides standard data transfer types as well as an
infrastructure for defining your own transfer types or supporting additional
platform-defined data types.</p>
<p><small>Java and all Java-based trademarks and logos are trademarks or registered trademarks of Sun
Microsystems, Inc. in the United States, other countries, or both.</small></p>
</body>
