啓動MainActivity
MainActivity: onCreate
MainActivity: onStart
MainActivity: onResume從MainActivity啓動SecondActivity
MainActivity: onPause//另一個Activity插入到MainActivity前面
SecondActivity: onCreate
SecondActivity: onStart
SecondActivity: onResume
MainActivity: onSaveInstanceState
MainActivity: onStop//MainActivity不可見點擊Home鍵
SecondActivity: onPause
SecondActivity: onSaveInstanceState
SecondActivity: onStop點擊圖標啓動
SecondActivity: onRestart
SecondActivity: onStart
SecondActivity: onResume點擊返回鍵
SecondActivity: onPause
MainActivity: onRestart
MainActivity: onStart
MainActivity: onResume
SecondActivity: onStop
SecondActivity: onDestroy