树（Tree类）应用实例如下：
1、简单树
public static void main (String [] args) {
Display display = new Display ();
Shell shell = new Shell (display);
shell.setLayout(new FillLayout());
final Tree tree = new Tree (shell, SWT.BORDER);
for (int i=0; i<4; i++) {
TreeItem iItem = new TreeItem (tree, 0);
iItem.setText ("TreeItem (0) -" + i);
for (int j=0; j<4; j++) {
TreeItem jItem = new TreeItem (iItem, 0);
jItem.setText ("TreeItem (1) -" + j);
for (int k=0; k<4; k++) {
TreeItem kItem = new TreeItem (jItem, 0);
kItem.setText ("TreeItem (2) -" + k);
for (int l=0; l<4; l++) {
TreeItem lItem = new TreeItem (kItem, 0);
lItem.setText ("TreeItem (3) -" + l);
}
}
}
}
shell.setSize (200, 200);
shell.open ();
while (!shell.isDisposed()) {
if (!display.readAndDispatch ()) display.sleep ();
}
display.dispose ();
}
2、类似资源管理器的树，其中包含鼠标双击事件
public static void main (String [] args) {
final Display display = new Display ();
final Shell shell = new Shell (display);
shell.setText ("Lazy Tree");
shell.setLayout (new FillLayout ());
final Tree tree = new Tree (shell, SWT.BORDER);
File [] roots = File.listRoots ();
for (int i=0; i<roots.length; i++) {
TreeItem root = new TreeItem (tree, 0);
root.setText (roots [i].toString ());
root.setData (roots [i]);//保存当前节点数据
new TreeItem (root, 0);//把当前节点作为目录节点
}
tree.addListener (SWT.Expand, new Listener () {
public void handleEvent (final Event event) {
final TreeItem root = (TreeItem) event.item;
TreeItem [] items = root.getItems ();
for (int i= 0; i<items.length; i++) {
if (items [i].getData () != null) return;
items [i].dispose ();
}
File file = (File) root.getData ();
File [] files = file.listFiles ();
if (files == null) return;
for (int i= 0; i<files.length; i++) {
TreeItem item = new TreeItem (root, 0);
item.setText (files [i].getName ());
item.setData (files [i]);
if (files [i].isDirectory()) {
new TreeItem (item, 0);
}
}
}
});
tree.addListener (SWT.MouseDoubleClick, new Listener () {
public void handleEvent (Event event) {
Point point = new Point (event.x, event.y);
TreeItem item = tree.getItem (point);
if (item != null) {
System.out.println ("Mouse down: " + item);
}
}
});
//根据Tree的大小更改shell的大小
Point size = tree.computeSize (300, SWT.DEFAULT);
int width = Math.max (300, size.x);
int height = Math.max (300, size.y);
shell.setSize (shell.computeSize (width, height));
shell.open ();
while (!shell.isDisposed ()) {
if (!display.readAndDispatch ()) display.sleep ();
}
display.dispose ();
}