11

片段是有趣的东西,但是,所以我想,一旦你了解了它们的怪癖,它们就是在多个设备上编写好的代码的宝贵工具。

但是,在修复方向更改错误时,我撞到了墙上。为了让我的片段工作,它需要访问属于它的视图,该视图包含 Activity 引导我进行愉快的追逐,试图找到 Activity 和 Fragment 生命周期如何交互。

我在它的onCreate()方法中向我的活动视图添加了一个片段:

// 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();
}

导致此活动->片段生命周期:

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,方向变化强调这通常不是这种情况,片段onCreate()方法在它的父活动之后不会被调用onCreate()。事实上,片段的第一个生命周期调用onAttach()发生在 Activity 甚至被创建之前(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这样。任何人都可以解释为什么Fragment.onAttach()在它包含 Activity 之前被调用?

我拥有的片段不需要访问其包含的活动(直到 UI 交互)按预期工作。

4

1 回答 1

10

啊,

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()

为什么有onAttach()一种我不知道的方法。特别是因为“附加”发生在活动之前。

我需要的方法当然是,onActivityCreated()它发生在Fragment 生命周期事件的“创建”集中的最终调用。

于 2012-01-04T15:52:18.967 回答