[news.eclipse.platform.swt] ProgressBar scroll Problem when run asynchro

[situchenghao@xxxxxxxxxxxx (Chenghao Situ)]

Hi,

I'm trying to use ProgressBar, but I met problem when I use INDETERMINATE 
mode and then start a asynchronism thread, see below code:

 Display display = new Display();
 final Shell shell = new Shell(display);
 shell.setBounds(100, 100, 400, 300);
		
 display.asyncExec(new Runnable(){

		public void run() {
				try {
					Thread.sleep(5000);
					//simulate long time task
				} catch (InterruptedException e) {
					//ignore
				}
			}
			
		});
 final ProgressBar progressBar = new ProgressBar(shell, 
SWT.INDETERMINATE);
 progressBar.setMaximum(100);
 progressBar.setMinimum(0);
 progressBar.setSelection(20);
 progressBar.setBounds(10, 15, 225, 20);
		
 shell.open();
 while(!shell.isDisposed())
 {
	if(!display.readAndDispatch())
	display.sleep();
 }

The progress bar seems be blocked, and start scroll till the asynchronism  
thread exit.
Using asyncExec() here as it need to update some UI elements when this 
thread is running.
Does some one know why the progressBar do not scroll when a asynchronism  
thread is running?
Is there some other solution can do same things?
What I want to do is when the back thread is running, it will update some 
UI element, and when it finished, it will notify UI to displose the 
progressBar.

Thanks.