MenuManager menuManager = new MenuManager(...);
ToolBar toolBar = new ToolBar(this...);
ToolItem toolItem = new ToolItem(toolBar...);
toolItem.addSelectionListener(new SelectionAdapter() {
	public void widgetSelected(SelectionEvent e) {
		final Menu menu = menuManager.createContextMenu(toolBar);
		...
		menu.setVisible(true);
	}
});

parent.addDisposeListener(new DisposeListener() {
	public void widgetDisposed(final DisposeEvent e) {
		menuManager.dispose();
		menuManager.removeAll();
	}
});