getSupportActionBar从片段ActionBarCompat内 [英] getSupportActionBar from inside of Fragment ActionBarCompat

问题描述

我开始了使用 AppCompat / ActionBarCompat 在 V7 支持库一个新项目。我试图找出如何使用 getSupportActionBar 从片段中。我承载片段活动来延长 ActionBarActivity ，但我没有看到碎片类似的辅助类。

I'm starting a new project that uses the AppCompat/ActionBarCompat in v7 support library. I'm trying to figure out how to use the getSupportActionBar from within a fragment. My activity that hosts the fragment extends ActionBarActivity, but I don't see a similar support class for Fragments.

这是我的片段中

    public class CrimeFragment extends Fragment {
          //...

          getActivity().getSupportActionBar().setSubtitle(R.string.subtitle); // getSupportActionBar is not defined in the v4 version of Fragment

          //...
    }

在谷歌页面使用它（<一href="http://android-developers.blogspot.in/2013/08/actionbarcompat-and-io-2013-app-source.html">http://android-developers.blogspot.in/2013/08/actionbarcompat-and-io-2013-app-source.html)说，不应该有任何的变化为 V4 片段。我需要投我所有的 getActivity（）调用一个 ActionBarActivity ？这似乎是设计不良。

The google page for using it (http://android-developers.blogspot.in/2013/08/actionbarcompat-and-io-2013-app-source.html) says there should be no changes for the v4 fragment. Do I need to cast all my getActivity() calls to an ActionBarActivity? That seems like poor design.

推荐答案

Fragment.onActivityCreated（...）后，你必须通过getActivity访问的有效活动（）。你需要将其转换为一个ActionBarActivity然后进行调用getSupportActionBar（）。

After Fragment.onActivityCreated(...) you'll have a valid activity accessible through getActivity(). You'll need to cast it to an ActionBarActivity then make the call to getSupportActionBar().

((ActionBarActivity)getActivity()).getSupportActionBar().setSubtitle(R.string.subtitle);

您需要做的转换。这不是设计差，则是向后兼容的。

You do need the cast. It's not poor design it's backwards compatibility.

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