Activity和Fragment回调研究

所有回调

Activity

• onCreate : 第一次创建的时候执行
• onContentChanged : 当Activity的布局改动时，即setContentView()或者addContentView()方法执行完毕时就会调用该方法
• onStart : 紧跟onCreate之后启动
• onRestart :当前Activity从不可见重新变为可见的状态时onRestart就会被调用
• onPostCreate :onCreate方法彻底执行完毕的回调
• onResume :窗口可见，并且即将与用户交互
• onPostResume :onResume方法彻底执行完毕的回调
• onPause : 整个窗口被半遮盖或者半透明的时候会执行
• onStop : 整个窗口被完全遮盖才会触发
• onDestroy : Activity即将被销毁，这是Activity生命周期的最后一个回调

程序启动运行并结束上述生命周期的方法执行顺序是这样的：

onCreate –> onContentChanged –> onStart –> onPostCreate –> onResume –> onPostResume –> onPause –> onStop –> onDestroy

Fragment

• onAttach 在Fragment与其Activity关联之后调用

• onCreate 该fragmet还没有获得Activity的onCreate()已完成的通知，所以不能将依赖于Activity视图层次结构存在性的代码放入此回调方法中

• onCreateView 为Fragment加载布局时调用。

• onViewCreated 紧跟OnCreateView之后被调用

• onActivityCreated ： 当Activity的onCreate()方法执行完之后，调用这个回调方法。

  onStart()\onResume()\onPause()\onStop()回调方法将和Activity的回调方法进行绑定，

---

• onStart

• onResume

• onPause

• onStop

---

• onDestroyView Fragment中的布局被移除时调用。

• onDestroy 不再使用Fragment时调用,Fragment仍然附加到Activity并可以找到，但是不能执行其他操作

• onDetach Fragme 当从Activity中解除Fragment的关联时，调用这个回调方法。

  ​

调用示例

没有加回退栈

• 打开一个附着Fragment的Activity

MainActivity: onCreate~~
Fragment1: onAttach
Fragment1: onCreate
Fragment1: onCreateView
Fragment1: onViewCreated
Fragment1: onActivityCreated
Fragment1: onStart
MainActivity: onStart~~~
MainActivity: onResume~~~
Fragment1: onResume

• 点击切换到另一个Fragment

Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment1: onDestroy
Fragment1: onDetach
Fragment2: onAttach
Fragment2: onCreate
Fragment2: onCreateView
Fragment2: onViewCreated
Fragment2: onActivityCreated
Fragment2: onStart
Fragment2: onResume

• 关闭Activity

Fragment2: onPause
MainActivity: onPause~~~
Fragment2: onStop
MainActivity: onStop~~~
Fragment2: onDestroyView
Fragment2: onDestroy
Fragment2: onDetach
MainActivity: onDestroy~~~

• 打开一个Activity

Fragment1: onPause
MainActivity: onPause~~~
Activity2: onCreate
Activity2: onStart~~~
Activity2: onResume~~~
Fragment1: onStop
MainActivity: onStop~~~

• 打开另一个附着Fragment的Activity

Fragment1: onPause
MainActivity: onPause~~~
Activity2: onCreate
Fragment3: onAttach
Fragment3: onCreate
Fragment3: onCreateView
Fragment3: onViewCreated
Fragment3: onActivityCreated
Fragment3: onStart
Activity2: onStart~~~
Activity2: onResume~~~
Fragment3: onResume
Fragment1: onStop
MainActivity: onStop~~~

• 回到之前的Activity

Fragment3: onPause
Activity2: onPause~~~
MainActivity: onRestart~~~
Fragment1: onStart
MainActivity: onStart~~~
MainActivity: onResume~~~
Fragment1: onResume
Fragment3: onStop
Activity2: onStop~~~
Fragment3: onDestroyView
Fragment3: onDestroy
Fragment3: onDetach
Activity2: onDestroy~~~

加了回退栈(反注册没了啊啊)

• 打开activity

MainActivity: onCreate
Fragment1: onAttach
Fragment1: onCreate
Fragment1: onCreateView
Fragment1: onViewCreated
Fragment1: register
Fragment1: onActivityCreated
Fragment1: onStart
MainActivity: onStart~~~
MainActivity: onResume~~~

• 切换Fragment

Fragment1: onResume
Fragment1: onPause
Fragment1: onStop
Fragment1: onDestroyView
Fragment2: onAttach
Fragment2: onCreate
Fragment2: onCreateView
Fragment2: onViewCreated
Fragment2: onActivityCreated
Fragment2: onStart
Fragment2: onResume

• 切换回原Fragment

Fragment2: onResume
Fragment2: onPause
Fragment2: onStop
Fragment2: onDestroyView
Fragment1: onCreateView
Fragment1: onViewCreated
Fragment1: register
Fragment1: onActivityCreated
Fragment1: onStart
Fragment1: onResume

可见:onAttach、onCreate、ondestroy和ondetach没有调用