CODEWITHSUNDEEP
javaasynchronousswt
tjsmith
tjsmith

Reputation: 749

How to update SWT GUI in asyncExec() call

In my SWT GUI, I would like to have a button that kicks off a job and while running that job, update a textbox that will show a log of the events of that job. However, my textbox does not update until the end of my asyncExec() call. In the example below, I would like for my textbox to be updated every second, but instead it gets all of the updates at once after 10 full seconds when it finishes executing.

Is there a way to achieve this?

private void UpdateUI()
{
    Display.getDefault().asyncExec(new Runnable() {
          @Override
          public void run() 
          {
            StringBuilder sb = new StringBuilder();
            for(int i=1; i<=10; i++)
            {
                sb.append("Running iteration " + i + "\n");
                txtLogBox.setText(sb.toString());
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
          }});
}

Upvotes: 1

Views: 1363

Answers (1)

Edward Thomson
Edward Thomson

Reputation: 78673

You're sleeping in the UI thread. You need to do your long-running work in a different thread and only post updates to the UI thread using asyncExec. For example:

new Thread(new Runnable() {
    public void run()
    {
        StringBuilder sb = new StringBuilder();

        for(int i=1; i<=10; i++)
        {
            sb.append("Running iteration " + i + "\n");
            final String result = sb.toString();

            Display.getDisplay().asyncExec(new Runnable() {
                public void run()
                {
                    txtLogBox.setText(result);
                }
            });

            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}).start();

Upvotes: 2

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