How to remove a mouse wheel listener in SWT

Question

I am trying to remove and replace a mouse wheel listener on a ScrolledComposite in SWT. The scrolled composite has a removeMouseWheelListener method, however it has no way of gaining access to a the mouse wheel listener to remove it. I have tried the getListeners() method:

MouseWheelListener mouseWheelListener = (MouseWheelListener) scrollable.getListeners(SWT.MouseWheel)[0];

but this produces an a casting error so getListeners must not retrieve the same type of listeners. I have tried creating a new listener and removing it from the ScrolledComposite:

MouseWheelListener scroller = new MouseWheelListener() {
    @Override
    public void mouseScrolled(MouseEvent e) {
        Point currentScroll = scrollable.getOrigin();
        scrollable.setOrigin(currentScroll.x, currentScroll.y - (e.count * 5));
    }
};
scrollable.removeMouseWheelListener(scroller);

This does not remove the listener though. Of course, if I had access to the original MouseWheelListener that was added this would not be a problem, but I don't. Thank you.

Why would you want to add and remove a listener? I don't understand. If you want a specific mouse wheel listener just add a new one by using addMouseWheelListener() method. But if you don't want your mouse wheel listener to do nothing just don't do anything in public void mouseScrolled( MouseEvent e ) — SomeDude
There is a MouseWheelListener that gets added to my ScrolledComposite. What I want to be able to do is remove that one, and put a new one in. If it is impossible to do this, why is there a removeMouseWheelListener() method? — Terrik

greg-449 greg-449 · Accepted Answer · 2015-12-04T21:07:20

getListeners will return a listener of type TypedListener for a mouse wheel listener.

TypedListener.getEventListener() will return the MouseWheelListener.

How to remove a mouse wheel listener in SWT

1 Answers