Android doc say:
\"When the system, rather than the user, shuts down an activity to conserve memory, ... \"
But how to simulate
For the purposes of debugging onRestoreInstanceState(), just change the screen orientation ([Ctrl]-[F11] in the emulator). Your activity will be destroyed and recreated, and the onSaveInstanceState()/onRestoreInstanceState() pair will be invoked.
onRestoreInstanceState()
onSaveInstanceState()