Skip to main content
aboutsummaryrefslogtreecommitdiffstats
blob: 0ed26e5ddc25108d633bd152197d9c2d98e2f981 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
/*******************************************************************************
 * Copyright (c) 2000, 2013 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Steven Spungin <steven@spungin.tv> - Bug 401439
 *******************************************************************************/
package org.eclipse.jface.viewers;

import org.eclipse.core.runtime.Assert;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.jface.internal.InternalPolicy;
import org.eclipse.jface.util.Policy;
import org.eclipse.swt.events.DisposeEvent;
import org.eclipse.swt.events.DisposeListener;
import org.eclipse.swt.widgets.Control;

/**
 * A content viewer is a model-based adapter on a widget which accesses its
 * model by means of a content provider and a label provider.
 * <p>
 * A viewer's model consists of elements, represented by objects.
 * A viewer defines and implements generic infrastructure for handling model 
 * input, updates, and selections in terms of elements.
 * Input is obtained by querying an <code>IContentProvider</code> which returns
 * elements. The elements themselves are not displayed directly.  They are
 * mapped to labels, containing text and/or an image, using the viewer's 
 * <code>ILabelProvider</code>.
 * </p>
 * <p>
 * Implementing a concrete content viewer typically involves the following steps:
 * <ul>
 * <li>
 * create SWT controls for viewer (in constructor) (optional)
 * </li>
 * <li>
 * initialize SWT controls from input (inputChanged)
 * </li>
 * <li>
 * define viewer-specific update methods
 * </li>
 * <li>
 * support selections (<code>setSelection</code>, <code>getSelection</code>)
 * </ul>
 * </p>
 */
public abstract class ContentViewer extends Viewer {

    /**
     * This viewer's content provider, or <code>null</code> if none.
     */
    private IContentProvider contentProvider = null;

    /**
     * This viewer's input, or <code>null</code> if none.
     * The viewer's input provides the "model" for the viewer's content.
     */
    private Object input = null;

    /**
     * This viewer's label provider. Initially <code>null</code>, but
     * lazily initialized (to a <code>SimpleLabelProvider</code>).
     */
    private IBaseLabelProvider labelProvider = null;

    /**
     * This viewer's label provider listener.
     * Note: Having a viewer register a label provider listener with
     * a label provider avoids having to define public methods
     * for internal events.
     */
    private final ILabelProviderListener labelProviderListener = new ILabelProviderListener() {
    	private boolean logWhenDisposed = true; // initially true, set to false
        
        @Override
		public void labelProviderChanged(LabelProviderChangedEvent event) {
        	Control control = getControl();
        	if (control == null || control.isDisposed()) {
    			if (logWhenDisposed) {
    				String message = "Ignored labelProviderChanged notification because control is diposed." + //$NON-NLS-1$
    						" This indicates a potential memory leak."; //$NON-NLS-1$
    				if (!InternalPolicy.DEBUG_LOG_LABEL_PROVIDER_NOTIFICATIONS_WHEN_DISPOSED) {
    					// stop logging after the first
    					logWhenDisposed = false;
    					message += " This is only logged once per viewer instance," + //$NON-NLS-1$
    							" but similar calls will still be ignored."; //$NON-NLS-1$
    				}
    				Policy.getLog().log(
    						new Status(IStatus.WARNING, Policy.JFACE, message,
    								new RuntimeException()));
    			}
        		return;
        	}
        	ContentViewer.this.handleLabelProviderChanged(event);
        }
    };

    /**
     * Creates a content viewer with no input, no content provider, and a
     * default label provider.
     */
    protected ContentViewer() {
    }

    /**
     * Returns the content provider used by this viewer, 
     * or <code>null</code> if this view does not yet have a content
     * provider.
     * <p>
     * The <code>ContentViewer</code> implementation of this method returns the content
     * provider recorded is an internal state variable. 
     * Overriding this method is generally not required; 
     * however, if overriding in a subclass, 
     * <code>super.getContentProvider</code> must be invoked.
     * </p>
     *
     * @return the content provider, or <code>null</code> if none
     */
    public IContentProvider getContentProvider() {
        return contentProvider;
    }

    /**
     * The <code>ContentViewer</code> implementation of this <code>IInputProvider</code> 
     * method returns the current input of this viewer, or <code>null</code>
     * if none. The viewer's input provides the "model" for the viewer's
     * content.
     */
    @Override
	public Object getInput() {
        return input;
    }

    /**
     * Returns the label provider used by this viewer.
     * <p>
     * The <code>ContentViewer</code> implementation of this method returns the label
     * provider recorded in an internal state variable; if none has been
     * set (with <code>setLabelProvider</code>) a default label provider
     * will be created, remembered, and returned.
     * Overriding this method is generally not required; 
     * however, if overriding in a subclass,
     * <code>super.getLabelProvider</code> must be invoked.
     * </p>
     *
     * @return a label provider
     */
    public IBaseLabelProvider getLabelProvider() {
        if (labelProvider == null) {
			labelProvider = new LabelProvider();
		}
        return labelProvider;
    }

    /**
     * Handles a dispose event on this viewer's control.
     * <p>
     * The <code>ContentViewer</code> implementation of this method disposes of this
     * viewer's label provider and content provider (if it has one).
     * Subclasses should override this method to perform any additional
     * cleanup of resources; however, overriding methods must invoke
     * <code>super.handleDispose</code>.
     * </p>
     *
     * @param event a dispose event
     */
    protected void handleDispose(DisposeEvent event) {
		if (contentProvider != null) {
			try {
				contentProvider.inputChanged(this, getInput(), null);
			} catch (Exception e) {
				// ignore exception
				String message = "Exception while calling ContentProvider.inputChanged from ContentViewer.handleDispose"; //$NON-NLS-1$
				message += " (" + contentProvider.getClass().getName() + ")"; //$NON-NLS-1$//$NON-NLS-2$
				Policy.getLog().log(new Status(IStatus.WARNING, Policy.JFACE, message, e));
			}
			contentProvider.dispose();
			contentProvider = null;
		}
		if (labelProvider != null) {
			labelProvider.removeListener(labelProviderListener);
			labelProvider.dispose();
			labelProvider = null;
		}
		input = null;
    }

    /**
     * Handles a label provider changed event.
     * <p>
     * The <code>ContentViewer</code> implementation of this method calls <code>labelProviderChanged()</code>
     * to cause a complete refresh of the viewer.
     * Subclasses may reimplement or extend. 
     * </p>
     * @param event the change event
     */
    protected void handleLabelProviderChanged(LabelProviderChangedEvent event) {
        labelProviderChanged();
    }

    /**
     * Adds event listener hooks to the given control.
     * <p>
     * All subclasses must call this method when their control is
     * first established.
     * </p> 
     * <p>
     * The <code>ContentViewer</code> implementation of this method hooks 
     * dispose events for the given control.
     * Subclasses may override if they need to add other control hooks;
     * however, <code>super.hookControl</code> must be invoked.
     * </p>
     *
     * @param control the control
     */
    protected void hookControl(Control control) {
        control.addDisposeListener(new DisposeListener() {
            @Override
			public void widgetDisposed(DisposeEvent event) {
                handleDispose(event);
            }
        });
    }

    /**
     * Notifies that the label provider has changed.
     * <p>
     * The <code>ContentViewer</code> implementation of this method calls <code>refresh()</code>.
     * Subclasses may reimplement or extend.
     * </p>
     */
    protected void labelProviderChanged() {
        refresh();
    }

    /**
     * Sets the content provider used by this viewer.
     * <p>
     * The <code>ContentViewer</code> implementation of this method records the 
     * content provider in an internal state variable.
     * Overriding this method is generally not required; 
     * however, if overriding in a subclass,
     * <code>super.setContentProvider</code> must be invoked.
     * </p>
     *
     * @param contentProvider the content provider
     * @see #getContentProvider
     */
    public void setContentProvider(IContentProvider contentProvider) {
        Assert.isNotNull(contentProvider);
        IContentProvider oldContentProvider = this.contentProvider;
        this.contentProvider = contentProvider;
        if (oldContentProvider != null) {
            Object currentInput = getInput();
            oldContentProvider.inputChanged(this, currentInput, null);
            oldContentProvider.dispose();
            contentProvider.inputChanged(this, null, currentInput);
            refresh();
        }
    }

    /**
     * The <code>ContentViewer</code> implementation of this <code>Viewer</code>
     * method invokes <code>inputChanged</code> on the content provider and then the
     * <code>inputChanged</code> hook method. This method fails if this viewer does
     * not have a content provider. Subclassers are advised to override 
     * <code>inputChanged</code> rather than this method, but may extend this method
     * if required.
     */
    @Override
	public void setInput(Object input) {
    	Control control = getControl();
		if (control == null || control.isDisposed()) {
			throw new IllegalStateException(
					"Need an underlying widget to be able to set the input." + //$NON-NLS-1$
							"(Has the widget been disposed?)"); //$NON-NLS-1$
		}
        Assert
                .isTrue(getContentProvider() != null,
                        "ContentViewer must have a content provider when input is set."); //$NON-NLS-1$

        Object oldInput = getInput();
        contentProvider.inputChanged(this, oldInput, input);
        this.input = input;

        // call input hook
        inputChanged(this.input, oldInput);
    }

    /**
     * Sets the label provider for this viewer.
     * <p>
     * The <code>ContentViewer</code> implementation of this method ensures that the
     * given label provider is connected to this viewer and the
     * former label provider is disconnected from this viewer.
     * Overriding this method is generally not required; 
     * however, if overriding in a subclass,
     * <code>super.setLabelProvider</code> must be invoked.
     * </p>
     *
     * @param labelProvider the label provider, or <code>null</code> if none
     */
    public void setLabelProvider(IBaseLabelProvider labelProvider) {
        IBaseLabelProvider oldProvider = this.labelProvider;
        // If it hasn't changed, do nothing.
        // This also ensures that the provider is not disposed
        // if set a second time.
        if (labelProvider == oldProvider) {
            return;
        }
        if (oldProvider != null) {
            oldProvider.removeListener(this.labelProviderListener);
        }
        this.labelProvider = labelProvider;
        if (labelProvider != null) {
            labelProvider.addListener(this.labelProviderListener);
        }
        refresh();

        // Dispose old provider after refresh, so that items never refer to stale images.
        if (oldProvider != null) {
    		internalDisposeLabelProvider(oldProvider);
        }
    }

	/**
	 * @param oldProvider
	 * 
	 * @since 3.4
	 */
	void internalDisposeLabelProvider(IBaseLabelProvider oldProvider) {
		oldProvider.dispose();
	}
}

Back to the top