片段/活动生命周期和方向变化

片段很有趣，但是，所以我想，一旦您了解了它们的怪癖，它们就是跨多个设备编写良好代码的宝贵工具。

然而，在修复方向改变错误时，我遇到了困难。为了让我的片段工作，它需要访问属于它的包含活动的视图，这引导我进行愉快的追逐，试图找到活动和片段生命周期如何交互。

我正在将一个片段添加到我的“活动”视图中onCreate() method:

// Only add a fragment once, as after it's been added it cannot be replaced (Even though there is a .replace() method. Which is a massive gaping hole in fragments as a technology if you ask me)
if(savedInstanceState == null) {
    MainMenuFragment menu= new MainMenuFragment();
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();   
    transaction.replace(R.id.menuFrame, menu);  
    transaction.commit();
}

导致这个Activity->Fragment生命周期：

01-04 15:17:27.226: W/SinglePaneActivity 0:   onCreate()
01-04 15:17:27.378: W/MainMenuFragment   0:   onAttach() to SinglePaneActivity 0
01-04 15:17:27.378: W/MainMenuFragment   0:   onCreate()
01-04 15:17:27.453: W/MainMenuFragment   0:   onActivityCreated()
01-04 15:17:27.476: W/MainMenuFragment   0:   onStart()
01-04 15:17:27.476: W/SinglePaneActivity 0:   onStart()
01-04 15:17:27.476: W/SinglePaneActivity 0:   onResume()
01-04 15:17:27.476: W/MainMenuFragment   0:   onResume()

然而，方向的变化凸显出通常情况并非如此，A 片段onCreate()方法在其父 Activity 之后不会被调用onCreate()。事实上，Fragment 的第一次生命周期调用onAttach()发生在 Activity 被创建之前（null作为参数传递）：

01-04 15:10:49.589: W/MainMenuFragment   0:   onPause()
01-04 15:10:49.589: W/SinglePaneActivity 0:   onPause()
01-04 15:10:49.589: W/MainMenuFragment   0:   onStop()
01-04 15:10:49.589: W/SinglePaneActivity 0:   onStop()
01-04 15:10:49.589: W/MainMenuFragment   0:   onDestroyView()
01-04 15:10:49.589: W/MainMenuFragment   0:   onDestroy()
01-04 15:10:49.589: W/MainMenuFragment   0:   onDetach()
01-04 15:10:49.609: W/SinglePaneActivity 0:   onDestroy()
01-04 15:10:49.617: W/MainMenuFragment   1:   onAttach() to null
01-04 15:10:49.617: W/MainMenuFragment   1:   onCreate()
01-04 15:10:49.617: W/SinglePaneActivity 1:   onCreate()
01-04 15:10:49.890: W/MainMenuFragment   1:   onActivityCreated()
01-04 15:10:49.917: W/MainMenuFragment   1:   onStart()
01-04 15:10:49.917: W/SinglePaneActivity 1:   onStart()
01-04 15:10:49.921: W/SinglePaneActivity 1:   onResume()
01-04 15:10:49.921: W/MainMenuFragment   1:   onResume()

我完全不知道为什么会发生这种情况。谁能解释一下为什么Fragment.onAttach()在创建包含 Activity 之前调用它吗？

我得到的片段不需要访问其包含的活动（直到 UI 交互）按预期工作。

Argh,

01-04 15:46:23.175: W/MainMenuFragment   0: onAttach() to SinglePaneActivity 0
01-04 15:46:23.179: W/MainMenuFragment   0: onCreate()
01-04 15:46:23.246: W/MainMenuFragment   0: onActivityCreated() with Activity SinglePaneActivity 0
01-04 15:46:23.269: W/MainMenuFragment   0: onStart()
01-04 15:46:23.269: W/SinglePaneActivity 0: onStart()

到底为什么有一个onAttach()方法我不知道。特别是因为“附加”发生在活动之前。

我需要的方法当然是，onActivityCreated()这是“Creation”集合中的最后一个调用片段生命周期事件 http://developer.android.com/images/fragment_lifecycle.png.