private ChangeListener<Boolean> viewerFocusChangeListener = new ChangeListener<Boolean>() {
		@Override
		public void changed(ObservableValue<? extends Boolean> observable,
				Boolean oldValue, Boolean newValue) {
			// cannot abort if no activeViewer
			if (activeViewer == null) {
				return;
			}


			// some more Code ...
			// ....
		}
	};

import org.eclipse.gef.mvc.fx.viewer.InfiniteCanvasViewer;

public class MyIfiniteCanvasViewer extends InfiniteCanvasViewer {
	@Override
	public boolean isViewerFocused() {
		return true;
	}
}

public class MyFxModule extends MvcFxModule {

 @Override
	protected void bindIViewer() {
		binder().bind(IViewer.class).to(MyIfiniteCanvasViewer.class);
	}

     /**
       Here are some more Code
      **/

}