Question

I have a Java SWT application and i’m using this snippet of code to display a message box.

    Display.getDefault().asyncExec(new Runnable() {

        @Override
        public void run() {
            try {

                MessageBox objError = new MessageBox(SysTray.shell, SWT.ICON_ERROR);
                objError.setMessage(strMessage);
                objError.open();
                SysTray.shell.getDisplay().dispose();
                System.exit(1);

            } catch (Exception e) {
                e.printStackTrace(); // Nothing to be handled here.
            }

        }

    });

This piece of code doesn’t get executed when my SWT UI isn’t created and therefore this block does not run. This has happened in situations where my UI thread has crashed.

How can I check if my UI is already created and if it isn’t, I’d like to still show the message box to the user.

Thanks.

Answer 1

The first parameter of MessageBox is the surrounding shell.

You have to define a Display, and a Shell within the Display, to show the Message Box.

Display display = new Display();
Shell shell = new Shell(display);
// Define message box
shell.open();
while (!shell.isDisposed()) {
    if (display.readAndDispatch()) {
        display.sleep();
    }
}
display.dispose();

Edited to add and answer the comment:

To determine if a Display and Shell exist –

    Display display = Display.getCurrent();
    if (display != null) {
        Shell[] shells = display.getShells();
    }