I was using a android 4.4.2 device to test with. With 4.1+ or higher there's another way to hide the status bar dynamically : http://developer.android.com/training/system-ui/status.html#41
//4.1+ Specific hiding of status bar
View decorView = getWindow().getDecorView();
int uiOptions = View.SYSTEM_UI_FLAG_FULLSCREEN;
decorView.setSystemUiVisibility(uiOptions);
I do not have the problem with the status bar popping up when adding a YoutubeFragment. Why the old code didn't work with YoutubeFragments, or even setting the Theme to
android:theme="@android:style/Theme.Holo.NoActionBar.Fullscreen"
, I have no idea though.