Programming things to remember 2014 Aug

Screen lock and activity rotation

I wanted to know, what fragment callbacks are called during different scenarios. I tested on Nexus 7 and on Samsung Galaxy SII.
Notable things:

• inflated view doesn't have proper size till an implicitly added callback is called (ViewTreeObserver). So even during onResume the measured width and height may be 0.
  
• the difference between the home press and rotation during fragment build down is the getActivity().isChangingConfigurations() flag
  
• the difference between the home press and the back press is the onSaveInstanceState() callback. Except on samsung, which keeps the fragment, no onDestroyView+onDestroy will be called. But because of this, no onGlobalLayout is called either.
  
• on samsung, the whole activity - which is behind the lock screen - gets all the callback events during rotation. So on nexus the onStart+onResume don't run until the lock screen is unlocked. On samsung, those callbacks are called right after the screen is turned on (and before it is unlocked). Likewise the rotation events, and because the lock screen on samsung is portrait only, it will recreate the fragment; and after unlocking it will recreate the fragment again (if the activity is fixed to landscape mode).
  

Nexus 7	Samsung S2
-- start new onAttach() onCreate() savedInstanceState: null onCreateView() savedInstanceState: null onActivityCreated() savedInstanceState: null onStart() rootView.getMeasuredWidth(): 0 onResume() rootView.getMeasuredWidth(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 672 -- back onPause() isChangingConfigurations: false onStop() onDestroyView() onDestroy() onDetach()	-- start new onAttach() onCreate() savedInstanceState: null onCreateView() savedInstanceState: null onActivityCreated() savedInstanceState: null onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 408 -- back onPause() isChangingConfigurations: false onStop() onDestroyView() onDestroy() onDetach()
-- start new onAttach() onCreate() savedInstanceState: null onCreateView() savedInstanceState: null onActivityCreated() savedInstanceState: null onStart() rootView.getMeasuredWidth(): 0 onResume() rootView.getMeasuredWidth(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 672 -- replace fragment onPause() isChangingConfigurations: false onStop() onDestroyView() -- reopen fragment onCreateView() savedInstanceState: null onActivityCreated() savedInstanceState: null onStart() rootView.getMeasuredWidth(): 0 onResume() rootView.getMeasuredWidth(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 672	-- start new onAttach() onCreate() savedInstanceState: null onCreateView() savedInstanceState: null onActivityCreated() savedInstanceState: null onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 408 -- replace fragment onPause() isChangingConfigurations: false onStop() onDestroyView() -- reopen fragment onCreateView() savedInstanceState: null onActivityCreated() savedInstanceState: null onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 408
-- rotate onPause() isChangingConfigurations: true onSaveInstanceState() onStop() onDestroyView() onDestroy() onDetach() onAttach() onCreate() savedInstanceState: Bundle[...] onCreateView() savedInstanceState: Bundle[...] onActivityCreated() savedInstanceState: Bundle[...] onStart() rootView.getMeasuredWidth(): 0 onResume() rootView.getMeasuredWidth(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 672	-- rotate onPause() isChangingConfigurations: true onSaveInstanceState() onStop() onDestroyView() onDestroy() onDetach() onAttach() onCreate() savedInstanceState: Bundle[...] onCreateView() savedInstanceState: Bundle[...] onActivityCreated() savedInstanceState: Bundle[...] onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 728
-- home press onPause() isChangingConfigurations: false onSaveInstanceState() onStop() onDestroyView() onDestroy() onDetach() -- reopen onAttach() onCreate() savedInstanceState: Bundle[...] onCreateView() savedInstanceState: Bundle[...] onActivityCreated() savedInstanceState: Bundle[...] onStart() rootView.getMeasuredWidth(): 0 onResume() rootView.getMeasuredHeight(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 672	-- home press onPause() isChangingConfigurations: false onSaveInstanceState() onStop() -- reopen onStart() rootView.getMeasuredHeight(): 728 onResume() rootView.getMeasuredHeight(): 728
-- lock onPause() isChangingConfigurations: false onSaveInstanceState() onStop() -- turn on -- unlock onStart() rootView.getMeasuredHeight(): 672 onResume() rootView.getMeasuredHeight(): 672	-- lock onPause() isChangingConfigurations: false onSaveInstanceState() onStop() -- turn on onStart() rootView.getMeasuredHeight(): 728 onResume() rootView.getMeasuredHeight(): 728 -- unlock
-- lock onPause() isChangingConfigurations: false onSaveInstanceState() onStop() -- turn on -- rotate onDestroyView() onDestroy() onDetach() onAttach() onCreate() savedInstanceState: Bundle[...] onCreateView() savedInstanceState: Bundle[...] onActivityCreated() savedInstanceState: Bundle[...] onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onPause() isChangingConfigurations: false onGlobalLayout() rootView.getMeasuredHeight(): 1141 -- unlock onResume() rootView.getMeasuredHeight(): 1141	-- lock (from landscape) onPause() isChangingConfigurations: false onSaveInstanceState() onStop() onDestroyView() onDestroy() onDetach() onAttach() onCreate() savedInstanceState: Bundle[...] onCreateView() savedInstanceState: Bundle[...] onActivityCreated() savedInstanceState: Bundle[...] onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onPause() isChangingConfigurations: false onGlobalLayout() rootView.getMeasuredHeight(): 728 -- turn on onResume() rootView.getMeasuredHeight(): 728 -- unlock onPause() isChangingConfigurations: true onSaveInstanceState() onStop() onDestroyView() onDestroy() onDetach() onAttach() onCreate() savedInstanceState: Bundle[...] onCreateView() savedInstanceState: Bundle[...] onActivityCreated() savedInstanceState: Bundle[...] onStart() rootView.getMeasuredHeight(): 0 onResume() rootView.getMeasuredHeight(): 0 onGlobalLayout() rootView.getMeasuredHeight(): 408