Get the GWT ScrollPanel to start its vertical scrollbar at the bottom

I know there are some questions out there about the GWT ScrollPanel and how it works, but allow me to explain the situation.

I'm working on a project to implement QoS on routers. 开发者_如何学JAVAI'm now at the developping stage of the project and I need to make a webinterface to add protocols such as ssh and http and give them their bandwidth.

To save memory usage and network traffic, I do not use GWT-EXT or Smart GWT. So to set the bandwidths I use a ScrollPanel with an empty SimplePanel in it (which is way too big), leaving only the scrollbar.

Now here's the problem: I want each scrollbar for each added protocol to start at the bottom, not the top. I can get it working through the code if I manually move the scrollbar first, then any function works, like a scrollToBottom(), or a setScrollPosition(). If I want to move scrollbars through code before moving the scrollbar manually, however, I can't call a function on it.

(I would post a picture but I can't yet - new user)

Summary:

So if I add a protocol (using a button called btnAjouter), the two slidebars (One for guaranteed bandwidth and one for the maximum bandwidth) for each protocol start at the top. I want them to start at the bottom on the load of the widget. Is there a way to do this? Thanks in advance!

Glenn

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Okay, my colleage found the solution. It's a rather dirty one, though. The thing is, the functions only work when the element in question is attached to the DOM. I did do a check with a Window.alert() to see if it was attached, and it was. But the prolem was that the functions were called to early, for example on a buttonclick it would've worked. The creation and attachment of the elements all happens very fast, so the Javascript can't keep up, this is the solution:

Timer t1 = new Timer()
        {
            @Override
            public void run() 
            {
                s1.getScroll().scrollToBottom();
                s2.getScroll().scrollToBottom();
            }
        };
t1.schedule(20);

Using a timer isn't the most clean solution around, but it works. s1 and s2 are my custom slidebars, getScroll() gets the ScrollPanel attached to it.

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You can extend ScrollPanel and override the onLoad method. This method is called immediately after a widget becomes attached to the browser's document.

@Override
protected void onLoad() {
    scrollToBottom();
}

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Could you attach a handler to listen to the add event and inside that handler do something like this:

panel.getElement().setScrollTop(panel.getElement().getScrollHeight());

"panel" is the panel that you add your protocol to. It doesn't have to be a ScrollPanel. An HTMLPanel will work.

You can wrap this method in a command and pass it to Schedule.scheduleDeferred if it needs to be called after the browser event loop returns:

Schedule.scheduleDeferred(new Scheduler.ScheduledCommand(
  public void execute() {
    panel.getElement().setScrollTop(panel.getElement().getScrollHeight());
  }
));