SWT制作下拉式ToolBar菜單代碼

SWT制作下拉式toolbar菜單按鈕的代碼片段:
    final ToolItem dropdown = new ToolItem(bar, SWT.DROP_DOWN);
    dropdown.setText("Drop-down");
    //一個popoupMenu
    final Menu menu = new Menu(shell, SWT.POP_UP);
    MenuItem choice = new MenuItem(menu, SWT.PUSH);
    choice.setText("Choices");
    dropdown.addListener(SWT.Selection, new Listener() {
    public void handleEvent(Event event) {
    if (event.detail == SWT.ARROW) {
    Rectangle rect = dropdown.getBounds();
    Point pt = new Point(rect.x, rect.y + rect.height);
    pt = bar.toDisplay(pt);
    menu.setLocation(pt.x, pt.y);
    menu.setVisible(true);
    }
    }
    });