OSGI + SWT: How to split the View (GUI) in many bundles

I'm writing a graphic application, with java, swt and osgi. The bundle A holds the application main window. Depending on the selection of the user, a different user interface must be loaded. That is, the different GUI are in different bundles. So the main bundle A calls the bundle B to draw the new graphic interface. The bundle B contains many classes, SWT controls that extend the Co开发者_如何学JAVAmposite class. This controls need a parent to draw to. The problem here is, the bundle B needs to draw on the bundle A. I tried to sends the parent composite that will hold the new interface from A to B, but when B creates the new control, it crashes.

Any idea? How to solve this problem?

Sounds like you're trying to setup some complicated cross dependency thing that isn't working out too well.

Are you aware of the Whiteboard pattern? You can read more here: http://www.osgi.org/wiki/uploads/Links/whiteboard.pdf

So based on that pattern let's say A is your 'main' bundle which loads the main UI. To keep things simple, let's say bundle A also exports the following interface:

public interface UIExtensionService {

    Control createExtension(Composite parent);

}

Bundle B (and C, D, E, F, etc) then registers appropriate implementations of this interface. You can use properties when you register the service to help your main bundle narrow down on a particular implementation for instance, if you want to show something specific based on a given user input.

Bundle A then uses the BundleContext to find an appropriate implementation of UIExtensionService and calls the createExtension method passing in the parent you want to use.

Hope that helps.