GeoQuiz has stopped

Hi everyone!
When i rotate screen (emulator), GeoQuiz has stopped
Has anyone ever encountered this problem?
In Logcat, when i rotate screen, only onCreate(Bundle) called,
why onStart() and onResume() not call?
I am here: Rotation and the Activity Lifecycle.

Please post your crash logs here.
By the way, please check whether each view with id in the layout folder is also included in the layout-land folder.

Sorry!.. I forget to change ImageButton to Button in Activity.
Thank you for your reply.