在Mac上无法使用选定控件上的Java SWT更改标签文本

Question

In my java swt application I have following code. On button select I need to change text of the label twice one is before running thread and other one is after thread finishes. It works on windows but on Mac it does not display the first text. Why this does not work on Mac?

button.addSelectionListener(new SelectionAdapter() {

        public void widgetSelected(SelectionEvent arg0) {
            statusLabel.setText("Running...");
            Thread background = new Thread() {
               @Override
               public void run() {
               // Long running task
               }
            };
            background.start();
            try {
                background.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            statusLabel.setText("Finished");
        }
    });

Answer 1

The call to Thread.join is blocking the UI thread which will cause it to stop responding. Exactly how much gets updated before this happens depends on the details on the SWT implementation on each platform.

You should update the UI from the background thread once the code has finished.

Something like:

button.addSelectionListener(new SelectionAdapter() {

   public void widgetSelected(SelectionEvent arg0) {

      statusLabel.setText("Running...");

      Thread background = new Thread() {
         @Override
         public void run() {
            // Long running task

            // Update UI from background thread
            Display.getDefault().asyncExec(() -> statusLabel.setText("Finished"));
         }
      };

      background.start();
  }
});