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 
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. | 