onCreate()->Created->onStart()->Started(visible)->onResume()->Resumed(visible)
->onPause()->Paused(partially visible)->onStop()->Stopped(hidden)->onDestroy()->Destroyed
Paused Activity通过onResume()，Stopped Activity通过onReStart()->onStart()
特殊场景
屏幕旋转时的Activity
Activity运行中--屏幕旋转-->onPause()->onStop()->onDestroy()->onCreate()->onStart()->onResume()->Activity运行中
低内存恶劣环境
Activity运行中-home键->onPause()->onStop()-低内存->onDestroy()->Activity killed
