Make app survive process death

[flamyoad]

Either by using SaveStateHandle or move initialization code to onResume callback.

Note that onResume can and will be called every time the screen is rotated. So be sure to not to call initialization code more than once.

[flamyoad]

• Intent passed to the activity can survive process death. The value passed before process death can still be retrieved in onRestoreInstanceState().

• SavedStateHandle only works with LiveData. Feels hacky to use LiveData.asFlow()

• onCreate() is called before onRestoreInstanceState() :)

• The solution used here is by checking whether the first MutableStateFlow in the ViewModel has its default value set. If it has default value, it either means the activity is initialized for first time, or it has undergone process death. It also helps that MutableStateFlow is distinctByDefault so we can just set the same value to the MutableStateFlow however many times we want in onResume() callback. It won't trigger the initialization code

• Checking if (savedInstanceState == null) to safeguard against screen rotation is a bad idea because savedInstanceState can survive process death.

  // This will mean your fragment will never be recreated after process death, and when user goes back to your app // through the Recents Apps screen
  if (savedInstanceState == null) { 
  val frameFragment = VerticalScrollingReaderFragment.newInstance()
  supportFragmentManager.beginTransaction()
      .replace(R.id.container, frameFragment, VerticalScrollingReaderFragment.TAG)
      .commit()
  }

Maybe try out Navigation Components someday