SWT滚动条上的鼠标事件

Question

Using standalone SWT Scrollbars is something of a hack (using this workaround ), but it can be done. Here's a snippet:

ScrolledComposite scrolledComposite = new ScrolledComposite(
                parent, SWT.V_SCROLL);
ScrollBar scrollbar = scrolledComposite.getVerticalBar();
Shell tip = new Shell(UserInterface.getShell(), SWT.ON_TOP
                | SWT.NO_FOCUS | SWT.TOOL);
// ..stylize and fill the tooltip..

Now what I'm trying to do is monitor when the user is interacting with the scrollbar. In particular, I want to know when the user is dragging the scrollbar—and when it has been released—in order to display an Office 2007-style tooltip revealing which page the position of the scrollbar corresponds with.

Presently, I have the following code which displays the tooltip:

scrollbar.addSelectionListener(new SelectionListener() {
    public void widgetDefaultSelected(SelectionEvent event) {}
    public void widgetSelected(SelectionEvent event) {
        tip.setVisible(true);
    }
}

It would seem logical then to have the tooltip disappear when the mouse button is released:

scrollbar.addListener(SWT.MouseUp, new Listener() {
    public void handleEvent(Event event) {
        tip.setVisible(false);
    }
});

However, neither scrollbar nor scrolledComposite seem to respond to the SWT.MouseUp event when the user interacts with the scrollbar.

I presently have a workaround that hides the tip after a timeout, but I'm not satisfied with this. Any insights would be most appreciated!

Answer 1

Scrollbar's javadoc said this:

When widgetSelected is called, the event object detail field contains one of the following values: SWT.NONE - for the end of a drag. SWT.DRAG. SWT.HOME. SWT.END. SWT.ARROW_DOWN. SWT.ARROW_UP. SWT.PAGE_DOWN. SWT.PAGE_UP. widgetDefaultSelected is not called.

So my suggestion is get your tooltip to appear and disappear is to check for the event.detail type.

public void widgetSelected(SelectionEvent event) {
    tip.setVisible(event.detail != SWT.NONE);
}

Answer 2

scrollBar.addSelectionListener(new SelectionListener() {
    public void widgetDefaultSelected(SelectionEvent e) {
    }

    public void widgetSelected(SelectionEvent e) {
        if (e.detail == SWT.NONE) {
            // end of drag
            System.out.println("Drag end");
        }
        else if (e.detail == SWT.DRAG) {
            // drag
            System.out.println("Currently dragging");
        }
    }
});

Hope this will help you... But I can see a problem with mousewheel use that throws multiple drag end events...

Answer 3

Paul,

try using addMouseEvent method from a Scrollable object. For example:

Scrollable scrollable = scrollbar.getParent();
scrollable.addMouseListener(new MouseListener () {
   void mouseDoubleClick(MouseEvent e) { ... }
   void mouseDown(MouseEvent e) { ... }
   void mouseUp(MouseEvent e)  { ... }
});

Actually, I don't know if this approach will work. But, it's an attempt. Good luck!