[news.eclipse.platform.swt] Re: ProgressBar scroll Problem when run asyn

[Anup Gokhale <anupgokhale@xxxxxxxxxxxxxx>]

display.asyncExec is not the solution for asynchronous threading. It 
just adds the request to the UI thread queue. For pure  "asynchronous 
threading", you should run your background task in a new thread created 
by implementing Runnable or you can use the Jobs API. you cab then 
display.asyncExec to update the UI from your new thred/job.

Regards,
Anup

Chenghao Situ wrote:
> 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.