title: Will activity run onDestroy when system kill it?
body: <p>I am wondering that will activity run the method "onDestroy" when killed by system?</p>
  
  <p>for example, when the state of "activity A" is onStop ( user may press the Home button directly ), 
  at the same time, system find out that the memory is not enough so system have to kill some  background processes to keep foreground activity alife, say system kill activity A. </p>
  
  <p>Will activity A run the method "onDestroy" in this situation? </p>