拖放gwt

Question

I'm trying to delete a widget from a panel when I drop that widget outside the panel. I looked up these tutorials and examples http://code.google.com/p/gwt-dnd/wiki/GettingStarted but I can't figure out how to set up the drop controller to drop it outside my panel.

Can you please give a hint or an idea?

Answer 1

If you instantiate a PickupDragController as

PickupDragController controller =
    new PickupDragController(pickupContainer, false);

and you drop your widgets outside the pickup container, then a VetoDragException is automatically thrown (as a result of that false in the contructor). See the JavaDoc or even the code in BoundaryDropController if interested).

You can then register a DragHandler and in its onDragEnd check if the exception occurred. If so, remove the widget. Something like:

class MyHandler implements DragHandler {
  // onPreviewDragStart, onDragStart, onPreviewDragEnd omitted.
  public void onDragEnd(DragEndEvent event) {
    if (event.getContext().vetoException != null) {
      // Not sure it works, but you get the idea.
      event.getContext().draggable.removeFromParent();
    }
  }
}

controller.addDragHandler(new MyHandler());

Answer 2

In the DropController (AbstractDropController) you have to define in the constructor, a element, where you can drop the elements. Do you have some code snippets to help you concrete?

PS: I have build some D&D with this library you mentioned, in my opinion, it is buggy and not so easy to start with. But I didn't found a better native D&D lib for GWT, we tried to wrap the jquery D&D. It is very fast and smooth, but hard to wrap.