现有两个Activity: Activity1,Activity2
先启动Activity1运行顺序为： Activity1 onCreate -> Activity1 onStart -> Activity1 onResume
用Intent从Activity1跳到Activity2运行顺序 ：
Activity1 onPause -> Activity2 onCreate -> Activity2 onStart -> Activity2 onResume ->Activity1 onStop -> Activity1 onDestroy
退出应用程序： Activity2 onResume ->Activity2 onStop -> Activity2 onDestroy