CODEWITHSUNDEEP
javaswtlistenermousemousewheel
Adam Green
Adam Green

Reputation: 171

SWT MouseWheelListener

I have done research into this for a while now and have found very little information on SWT MouseWheelListeners. Looking to see if any of you have encountered this or have a link to something that could help explain them.

I am trying to find out information on the SWT MouseWheelListener and how it is used appropriately. I am attempting to use the MouseWheelListener to create a zoom effect on a composite which draws multiple composite objects on it.

In essence, when wheeling up zoom in by redrawing the canvas at twice normal size, repainting objects on the canvas in a proportional layout, and moving the focus to the point wheeled on.

My questions are the following: Is it possible to use a MouseWheelListener on a Composite or is the listener only for objects like scrolled composites (I know the method is there; nothing is happening when I attempt to scroll on my object (including at debug)? How to kick off a MouseScrolledEvent on a Composite if possible? How to differentiate between wheel up and wheel down (e.count is positive for up & negative for down)?

Code follows:

public TagCloudComposite(Composite parent, int style) {
    super(parent, style);
    addMouseWheelListener(new MouseWheelListener() {
        public void mouseScrolled(MouseEvent e) {
            int count = e.count;
            System.out.println(count);
            // int direction = (Math.abs(count) > 0) ? UP : DOWN;
            // changeBackground(direction);
        }
    });
    this.setLayout(new FillLayout());
    this.setMinWeight(1);
    this.setMaxWeight(100);
    c = new Composite(this, SWT.NONE);
    this.setSize(300, 200);
}

Upvotes: 1

Views: 5700

Answers (2)

Cley Faye
Cley Faye

Reputation: 61

It is possible to use the MouseWheelListener on a canvas; the only thing is that the event trigger only on the component with the focus.

A canvas don't usually get focus, unless you add a key listener to it (even an empty one).

(I know the question is quite old, but faced with the same issue google directed me there so here's a solution).

Upvotes: 2

bigfatbrowncat
bigfatbrowncat

Reputation: 21

Yes, you're right. "Count" here means number of scroll lines (3 or -3 by default in Windows)

Upvotes: 2

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