CODEWITHSUNDEEP
javaswingdrag-and-dropawt
Vlad Topala
Vlad Topala

Reputation: 916

Can I listen for all drag & drop events in java?

I would like to listen for all the drag and drop events on Swing.

One way I managed to listen for drag events was by adding:

final long mask = AWTEvent.MOUSE_EVENT_MASK + AWTEvent.MOUSE_MOTION_EVENT_MASK;

AWTEventListener eventListener = new AWTEventListener() {
    public void eventDispatched(final AWTEvent event) {}
};
Toolkit.getDefaultToolkit().addAWTEventListener(eventListener, mask);

but this does not get drop events, not even release events from the mouse when dropping. Is there a way to intercept all drag and drop events in the application, not on each component separately?

Upvotes: 5

Views: 2057

Answers (1)

kleopatra
kleopatra

Reputation: 51525

This is not a complete (maybe not even a feasable ;-) solution to your requirement, but might get you started.

As noted, all low-level input events (like mouseEvents, depending on the underlying OS there might be others as well) are swallowed by the dnd-subsystem during a drag. Internally, they are transformed into DragXXEvents which in turn are fired by the DragSource. The dragSource is a singleton that's re-used across all dnd operations. So a way to go might be:

  • grab the global DragSource
  • register a DragSource/Motion/Listener
  • monitor the information from the DragSourceEvent as needed

Some snippet:

DragSource source = DragSource.getDefaultDragSource();
DragSourceMotionListener dsml = new DragSourceMotionListener() {

    @Override
    public void dragMouseMoved(DragSourceDragEvent dsde) {
        debug(dsde);
    }
};
source.addDragSourceMotionListener(dsml);

// just some logging
protected void debug(DragSourceEvent dsde) {
    DragSourceContext context = dsde.getDragSourceContext();
    Component source = context.getComponent();
    String text = source != null ? source.getName() : "none";
    LOG.info(text + " x/y " + dsde.getX() + "/" + dsde.getY());
}

Still a lot a work ahead ...

Upvotes: 2

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