I get the Error
Unable to start activity ComponentInfo{de.androidbuch.activiti/de.androidbuch.activiti.task.Activity}: android.view.InflateException: Binar
I was having the same problem as you are facing. None of the tips on top helped me. Later, I found that all I had to do is fix my imports from:
import android.app.Fragment;
to:
import android.support.v4.app.Fragment;