一般正常啓動:
onCreate --> onStart --> onResume
打開另一個Activity2:
onPause(1) --> onCreate(2) --> onStart(2) --> onResume(2) --> onStop(1)
返回原Activity1:
onPause(2) --> onRestart(1) --> onStart(1) --> onResume(1) --> onStop(2) --> onDestroy(2)
退出Activity1:
onPause --> onStop --> onDestroy