Eclipse RCP which shell to use for popups

Question

I am trying to get hold of a shell in Eclipse RCP and bring up popups in my application and had gone through several resources/tutorials to achieve the task but without much luck.

Tried:

Display.getCurrent().getActiveShell();

or

Display.getDefault().getActiveShell();

or

  PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell();

or sometimes even

 Display.getDefault().getShells()[0];

But different things seem to work in different situations.

Resources online have different views and most things I find say you shouldn't really use the Display class at all but I am trying to bring up a popup from within an eclipse Job. It's got to the end and failed and the popup needs to be displayed using:

Code:

        Display.getCurrent().syncExec(new Runnable() {

            @Override
            public void run() {

                    MessageDialog.openError(Display.getDefault().getActiveShell(), "Publish", e.getMessage());


            }
        });
    }

The popup is inside a Runnable being executed from a Thread started from an Eclipse Job. It's complex but necessary to provide progress bar updates whilst calling a synchronous method on a server.

It doesn't work and I don't know why. Just getting a null from the getActiveShell() call.

The real question though isn't 'why doesn't my code work' but was is the definitively correct way to get a shell for a popup in Eclipse RCP framework, and especial in situations where you can't access a workbench?

Answer 1

Looking though the Eclipse source there does not seem to be a definitive way. The closest is some variant of

PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell();

Even if this returns null that is still acceptable to MessageDialog.

DebugUIPlugin has this more elaborate version:

public static Shell getShell() {
  IWorkbenchWindow window = PlatformUI.getWorkbench().getActiveWorkbenchWindow();
  if (window == null) {
    IWorkbenchWindow[] windows = PlatformUI.getWorkbench().getWorkbenchWindows();
    if (windows.length > 0) {
       return windows[0].getShell();
    }
  }
  else {
    return window.getShell();
  }
  return null;
}

Use of MessageDialog from a Job is rare in the Eclipse source. As the Job runs asynchronously a popup from the Job could be rather unexpected.

In Eclipse 4 applications if you can get the IEclipseContext there should be an IShellProvider in the context. e4 apps can also use StatusReporter which does not need a shell.