该activity有一个默认的Fragment
经过实例测试在不同场景中的生命周期方法调用如下
1.开始运行：onCreate（activity）--> onStart(activity) --> onAttach(fragment) --> onCreate(fragment) --> onCreateView(fragment) --> onViewCreated(fragment) --> onActivityCreated(fragment) --> onStart(fragment) -->onResume(activity) --> onPostResume(activity)
2.屏幕锁定：onPause（activity）--> onPause(fragment) --> onStop(activity) --> onStop(fragment) -->
3.重新回到应用中：onRestart（activity）--> onStart(activity) --> onStart(fragment) --> onResume(activity) --> onPostResume(activity)
4.退出：onPause（activity） --> onPause(fragment) --> onStop(activity) --> onStop(fragment) --> onDestroy(activity)
--> onDestroyView(fragment) --> onDestroy(fragment) --> onDetach(fragment)