I get the Error
Unable to start activity ComponentInfo{de.androidbuch.activiti/de.androidbuch.activiti.task.Activity}: android.view.InflateException: Binar
If you are adding Fragment statically that is, in xml, then you might have missed to implement OnFragmentInteractionListener in your Activity class. Then the interface implementation would solve the problem. If you are adding Fragment dynamically, that is, in java class then this is not the solution. Because IDE itself will not allow you to proceed without implementing required interfaces.