How do I detect that a SWT dialog has been opened and is visible?

Question

I have an SWT WizardDialog with a number of pages. When this dialog first opens I have to do a check for some conditions and if those conditions are met I need to show a popup over the freshly opened dialog.

So I have this code to listen for SWT.Show event. The event listener responds to SWT.Show to conduct its tests and show a message box:

  final WizardDialog dialog = new WizardDialog(shell, wizard);
  dialog.setTitle("New Wizard");
  dialog.create();
  dialog.getShell().addListener(SWT.Show, new Listener()
  {
     private boolean firstShowing = true;

     @Override
     public void handleEvent(Event event)
     {
        if (firstShowing && someConditionExists())
        {
          MessageBox messageBox = new MessageBox(dialog.getShell(), SWT.OK
                 | SWT.ICON_WARNING);
          messageBox.setMessage("Test");
          messageBox.open();
          firstShowing = false;
        }
     }
  });
  dialog.open();

Except it's called too soon! The dialog is not visible when the handler is called. My message box appears before the dialog is visible and the dialog only appears when I dismiss the message box.

So clearly the SWT.Show is unreliable, at least on Windows where I'm running it. I've also tried putting this code into a ShellListener on the activation but that happens even before the SWT.Show example above.

So how do I reliably show a message box when the dialog is made visible?

Plan B is a dirty timer based hack where a timer is set to fire 200 ms into the future and hope that it triggers when the dialog is visible but obviously this could introduce it's own issues.

score 4 · Answer 1 · answered Aug 16 '12 at 05:38

I'm using in similar situation (need that appStarted() is called after application window is visible) something like below.

public class App extends ApplicationWindow {

    @Override
    protected Control createContents(Composite parent) {
        // ...

        getShell().addShellListener(new ShellAdapter() {

            @Override
            public void shellActivated(ShellEvent shellevent) {
                if (!started) {
                    Shell s = (Shell) shellevent.getSource();
                    s.setVisible(true);
                    appStarted();
                    started = true;
                }
            }
        });
    }
}

Maybe You can use the same like below:

final WizardDialog dialog = new WizardDialog(shell, wizard);
dialog.setTitle("New Wizard");
dialog.create();
dialog.getShell().addShellListener(new ShellAdapter() {

    @Override
    public void shellActivated(ShellEvent shellevent) {

        if (firstShowing && someConditionExists()) {
            Shell s = (Shell) shellevent.getSource();
            s.setVisible(true);

            MessageBox messageBox = new MessageBox(dialog.getShell(), SWT.OK | SWT.ICON_WARNING);
            messageBox.setMessage("Test");
            messageBox.open();
            firstShowing = false;
        }

    }
});
dialog.open();

score 2 · Answer 2 · answered Sep 12 '11 at 18:42

2

Instead of hooking the SWT.Show event, you may get more luck with hooking a PaintListener on to your dialog's Composite. (You'll probably want to unhook it during the first execution.)

answered Sep 12 '11 at 18:42

Edward Thomson

74,857
14
158
187

score 1 · Answer 3 · answered Sep 10 '15 at 19:36

1

I know that this is an old thread. But in case someone finds it useful, I found that overriding Dialog.create() rather than Dialog.open() worked for me.

answered Sep 10 '15 at 19:36

Geoff Alexander

419
5
13

Alexander Khomenko · Answer 4 · 2021-04-07T08:22:17.870

it's called too soon!

I also run recently in the same trouble. The code was executed too early - my upload action (which I wanted to start automatically under some conditions) was started before the page was displayed.

This happens because the page can only be shown after the code in the SWT.SHOW listener or in the inherited setVisible() method is completed.

@Override
public void setVisible(boolean visible) {
    if (visible) {
        org.eclipse.ui.progress.UIJob("Auto start the upload") {
            @Override
            public IStatus runInUIThread(IProgressMonitor monitor) {
                if (isAutoStartQcUploadSelected)
                    startUpload();
                return Status.OK_STATUS;
            }
        };
        uiJob.schedule();
    }
    super.setVisible(visible);
}

org.eclipse.ui.progress.UIJob as described FAQ_Can_I_make_a_job_run_in_the_UI_thread has solved the issue.

P.S.: Yes, I know that's an old question :-) But it is the first one propesed by google and the hint with the UI Job was missing.

jefflunt · Answer 5 · 2011-09-12T14:40:20.630

1

What about overriding dialog.open() methodon your WizardDialog class? The first line of the overridden method would call super.open(), which would make it visible. Just put your custom code after that, in the .open() method.

The issue with the approach you're taking above appears to be that it responds to a Show event, which is simply notification that Show has been requested, not that the dialog is visible. The Show event could very well be designed to allow you to know when something is about to be shown, and take some action before that happens, as you've experienced.

edited Sep 12 '11 at 14:40

answered Sep 12 '11 at 14:11

jefflunt

33,527
7
88
126

1

Agreed 100% - though I think you meant to write super.open(). – Edward Thomson Sep 12 '11 at 14:36
3

I can't override Window.open() (which is the method for opening a dialog) because the dialog is blocking. The open() method invokes shell.open() followed by runEventLoop() which is a private method that pumps messages until the dialog is disposed of. If runEventLoop() were protected I could insert something in there probably but because it isn't I can't. At present I'm using a timer instead to popup a message box but obviously that isn't to my liking at all. – locka Sep 12 '11 at 14:43
So, if you override `Window.open`, it won't return control to you until after you've acknowledged the Dialog? Ok, let me think a bit more on this... – jefflunt Sep 12 '11 at 16:44
Can you pass a reference to the shell out via the event, and then use `if (!shell.isDisposed()) { ...your code... }` to detect the dialog being open? (see the sample code for the custom dialog, and how it uses the `open` method - getting a reference to the shell this way would work?) http://help.eclipse.org/helios/index.jsp?topic=/org.eclipse.platform.doc.isv/reference/api/org/eclipse/swt/widgets/Dialog.html – jefflunt Sep 12 '11 at 16:50
You could turn off block on open, call Dialog#open and then run the event loop yourself (`while (! Display.readAndDispatch()) { Display.sleep(); }`). – Edward Thomson Sep 12 '11 at 18:38

score 0 · Answer 6 · edited May 23 '17 at 12:16

The code of marioosh can be further improved, by storing the ShellAdapter in a variable.

Remove the ShellAdapter when the listener is triggered for the first time.

The variable started is no longer needed.

The statement s.setVisible(true); is not necessary, because this event is just triggered when the shell gets visible.

public class App extends ApplicationWindow {

    @Override
    protected Control createContents(Composite parent) {
        // ...
        ShellAdapter shellActivatedAdapter = new ShellAdapter() {

            @Override
            public void shellActivated(ShellEvent shellevent) {
                shellevent.getSource().removeShellListener(shellActivatedAdapter);
                appStarted();
            }
        };

        getShell().addShellListener(shellActivatedAdapter);
    }
}

How do I detect that a SWT dialog has been opened and is visible?

6 Answers6

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