Recipe 10.6 Handling Tree Events

     

10.6.1 Problem

You need to know when the user selects an item in a tree widget.

10.6.2 Solution

Add a new listener to the Tree widget, using the addListener or addSelectionListener methods .

10.6.3 Discussion

As an example, we'll add a listener to the tree developed in the previous recipe. We'll also add a text widget to display the user's selection, as shown in Example 10-3.

Example 10-3. SWT trees
 package org.cookbook.ch10; import org.eclipse.swt.*; import org.eclipse.swt.widgets.*; public class TreeClass {     public static void main(String[] args)     {         Display display = new Display( );         Shell shell = new Shell(display);         shell.setText("Tree Example");  final Text text = new Text(shell, SWT.BORDER);         text.setBounds(0, 270, 290, 25);  final Tree tree = new Tree(shell, SWT.BORDER  SWT.V_SCROLL                SWT.H_SCROLL);         tree.setSize(290, 260);         shell.setSize(300, 330);         for (int loopIndex0 = 0; loopIndex0 < 10; loopIndex0++)         {             TreeItem treeItem0 = new TreeItem(tree, 0);             treeItem0.setText("Level 0 Item " + loopIndex0);             for (int loopIndex1 = 0; loopIndex1 < 10; loopIndex1++)             {                 TreeItem treeItem1 = new TreeItem(treeItem0, 0);                 treeItem1.setText("Level 1 Item " + loopIndex1);                 for (int loopIndex2 = 0; loopIndex2 < 10; loopIndex2++)                 {                     TreeItem treeItem2 = new TreeItem(treeItem1, 0);                     treeItem2.setText("Level 2 Item " + loopIndex2);                 }             }         }  tree.addListener(SWT.Selection, new Listener( )         {             public void handleEvent(Event event)             {                 text.setText(event.item + " was selected");             }         });         shell.open( );         while (!shell.isDisposed( ))         {             if (!display.readAndDispatch( ))                 display.sleep( );         }         display.dispose( );  } } 

With the new listener and the text widget to display selection events, the TreeApp example can display selections the user makes, as shown in Figure 10-5.

Figure 10-5. Catching tree selection events
figs/ecb_1005.gif

10.6.4 See Also

Recipe 10.5 on creating SWT trees; Recipe 10.7 on adding checkboxes to tree items; Recipe 10.8 on adding images to tree items.



Eclipse Cookbook
Inside XML (Inside (New Riders))
ISBN: 596007108
EAN: 2147483647
Year: 2006
Pages: 232
Authors: Steve Holzner

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