appl.getContext().put( MyEditor.class, this );

IPartListener partListener = new IPartListener() {
	public void partVisible(MPart part) {}
	public void partHidden(MPart part) {}
	public void partDeactivated(MPart part) {}
	public void partBroughtToTop(MPart part) { registerObject(part); }
	public void partActivated(MPart part) {	registerObject(part); }
};
private void registerObject(MPart part) {
	if( part.getContext().get( MyEditor.class) != MyEditor.this ){
		return;
	}
	appl.getContext().set( MyEditor.class, MyEditor.this );
}

if( MyEditor.this == appl.getContext().get( MyEditor.class )){
	appl.getContext().set( MyEditor.class, null );
}
partService.removePartListener(partListener);

PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage().getActiveEditor()

@Inject
public void setEditor( @Optional MyEditor editor ){
  //...
}