FileDialog Parent

Creation of a FileDialog requires a Frame parent. If this is done from an overridden MenuButton then the Frame has to be found by walking up the parent tree from the MenuButton:

class OpenButton extends MenuButton {
   public boolean action(Event evt, Object what) {
      Object parent = evt.target;

      while (parent != null && 
             !(parent instanceof Frame)) {
         parent = ((MenuComponent) 
                   parent).getParent();
      }
      new FileDialog((Frame) parent, 
                     "Open File");
   }
}