Currently working on android application which uses youtube api to show video. In this application I\'m showing video in fragment using youtubeplayerfragment. When I click o
for saving video state use 
   android:configChanges="keyboardHidden|orientation|screenSize" in your
   activity tag where your fragment is appearing eg:
<activity android:name=".activities.MainActivity"
   android:configChanges="keyboardHidden|orientation|screenSize">
in your onFullscreen method check if player fullscreen set or not
@Override
       public void onFullscreen(boolean b) {
           Log.e("onFullscreen",""+b);
           if(b)
               fullscreen=1;
           else fullscreen=2;
       } 
in your backpress bethod check if full screen is set then set to false
 @Override
           public void onBackPressed() {
               if(fullscreen==1)
               {
                   if(this.player!=null)
                       youTubePlayer.setFullscreen(false);
               }
               else
                   super.onBackPressed();
           } 
i hope it helps you, sorry for my bad english