Android 为什么ViewRecycler在测量时爆炸

我有一个ViewRecycler，它在一个片段中使用CardView，该片段是ActionBarActivity上的ViewPager的一部分。所有这些都来自支持库

当我试图打开应用程序时，它会崩溃，出现以下异常。是否有我错过的已知问题或解决方案

java.lang.NullPointerException
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764)
        at android.view.View.measure(View.java:16736)
        at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1456)
        at android.view.View.measure(View.java:16736)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5178)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:16736)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5178)
        at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453)
        at android.view.View.measure(View.java:16736)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5178)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:16736)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5178)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:16736)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5178)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2392)
        at android.view.View.measure(View.java:16736)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2095)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1208)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1394)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1095)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6010)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:799)
        at android.view.Choreographer.doCallbacks(Choreographer.java:599)
        at android.view.Choreographer.doFrame(Choreographer.java:559)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:784)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:157)
        at android.app.ActivityThread.main(ActivityThread.java:5872)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:852)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:668)
        at dalvik.system.NativeStart.main(Native Method)

我尝试过各种各样的建议，比如在我有相对论的地方使用线性布局，但没有任何帮助，所以我又返回了。我的布局和代码如下

Gradle

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.0.0'
    compile 'com.android.support:cardview-v7:21.0.+'
    compile 'com.android.support:recyclerview-v7:21.0.+'
}

活动

public class LaunchActivity extends ActionBarActivity {

    private SectionsPagerAdapter mSectionsPagerAdapter;
    private ViewPager mViewPager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_launch);
        mSectionsPagerAdapter = new SectionsPagerAdapter(this, getSupportFragmentManager());
        mViewPager = (ViewPager) findViewById(R.id.pager);
        mViewPager.setAdapter(mSectionsPagerAdapter);
    }

    ...
}

活动布局

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="@+id/pager"
android:layout_width="match_parent" android:layout_height="match_parent"
tools:context="com.me.LaunchActivity" />

public class RotaFragment extends Fragment {

    private RecyclerView mCardRecycler;

    public static RotaFragment newInstance() {
        ...
    }

    public RotaFragment() { }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_rota, container, false);
        mCardRecycler = (RecyclerView) rootView.findViewById(R.id.card_recycler);
        return rootView;
   }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        List<WorkingFortnight> dummy = new ArrayList<>();
        ....
        mCardRecycler.setLayoutManager( new LinearLayoutManager(getActivity()) );
        mCardRecycler.setAdapter(new RotaCardAdapter(dummy));
    }
}

<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/card_recycler"
    android:background="@drawable/activity_bg"
    android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

片段

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="@+id/pager"
android:layout_width="match_parent" android:layout_height="match_parent"
tools:context="com.me.LaunchActivity" />

public class RotaFragment extends Fragment {

    private RecyclerView mCardRecycler;

    public static RotaFragment newInstance() {
        ...
    }

    public RotaFragment() { }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_rota, container, false);
        mCardRecycler = (RecyclerView) rootView.findViewById(R.id.card_recycler);
        return rootView;
   }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        List<WorkingFortnight> dummy = new ArrayList<>();
        ....
        mCardRecycler.setLayoutManager( new LinearLayoutManager(getActivity()) );
        mCardRecycler.setAdapter(new RotaCardAdapter(dummy));
    }
}

<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/card_recycler"
    android:background="@drawable/activity_bg"
    android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

公共类RotaFragment扩展片段{
私人垃圾回收公司；
公共静态RotaFragment newInstance（）{
...
}
公共旋转碎片（）{}
@凌驾
CreateView上的公共视图（布局、充气机、视图组容器、捆绑包保存状态）{
视图根视图=充气机。充气（R.layout.fragment_rota，容器，错误）；
mCardRecycler=（RecyclerView）rootView.findViewById（R.id.card\u recycler）；
返回rootView；
}
@凌驾
已创建视图上的公共void（视图，@Nullable Bundle savedInstanceState）{
super.onViewCreated（视图，savedInstanceState）；
List dummy=new ArrayList（）；
....
setLayoutManager（新的LinearLayoutManager（getActivity（））；
setAdapter（新的RotaCardAdapter（虚拟））；
}
}

片段布局

<android.support.v4.view.ViewPager xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools" android:id="@+id/pager"
android:layout_width="match_parent" android:layout_height="match_parent"
tools:context="com.me.LaunchActivity" />

public class RotaFragment extends Fragment {

    private RecyclerView mCardRecycler;

    public static RotaFragment newInstance() {
        ...
    }

    public RotaFragment() { }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_rota, container, false);
        mCardRecycler = (RecyclerView) rootView.findViewById(R.id.card_recycler);
        return rootView;
   }

    @Override
    public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        List<WorkingFortnight> dummy = new ArrayList<>();
        ....
        mCardRecycler.setLayoutManager( new LinearLayoutManager(getActivity()) );
        mCardRecycler.setAdapter(new RotaCardAdapter(dummy));
    }
}

<android.support.v7.widget.RecyclerView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/card_recycler"
    android:background="@drawable/activity_bg"
    android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin" android:paddingBottom="@dimen/activity_vertical_margin"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
/>

适配器（在ViewRecycler上设置以设置CardView）

公共类RotaCardAdapter扩展了RecyclerView.Adapter{
私人名单MROTA；
公共RotaCardAdapter（列出ROTA）{
mRotas=rotas；
}
@凌驾
附加ToRecyclerView（RecyclerView RecyclerView）上的公共无效{
super.onAttachedToRecyclerView（recyclerView）；
}
@凌驾
public RotaViewHolder onCreateViewHolder（视图组父级，int-viewType）{
视图v=LayoutInflater.from（parent.getContext（））.flate（R.layout.rota_卡，parent，false）；
返回新的Rotaviewowlder（v）；
}
@凌驾
BindViewHolder上的公共无效（RotaViewHolder，内部位置）{
工作两周rota=mRotas.get（位置）；
固定时间（…）；
}
公共类RotaViewHolder扩展了RecyclerView.ViewHolder{
私有文本视图选项；
私人RotaListAdapter；
公共旋转支架（视图五）{
超级（五）；
...
mList.setAdapter（…）；
}
...
}

适配器视图（卡）

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我意识到这是一个复杂的嵌套布局，但我希望有人知道我在这里所做的一些事情的一些问题，也许某些视图不能嵌套，但我的搜索中没有出现任何问题，简化测试到目前为止没有帮助。

出现空指针是因为回收器视图的布局管理器为空

您必须尽快设置layoutmanager：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_rota, container, false);
    mCardRecycler = (RecyclerView) rootView.findViewById(R.id.card_recycler);
    List<WorkingFortnight> dummy = new ArrayList<>();
    ....
    mCardRecycler.setLayoutManager( new LinearLayoutManager(MyApplication.getApplicationContext()) );
    mCardRecycler.setAdapter(new RotaCardAdapter(dummy));
    return rootView;
}

@覆盖
CreateView上的公共视图（布局、充气机、视图组容器、捆绑包保存状态）{
视图根视图=充气机。充气（R.layout.fragment_rota，容器，错误）；
mCardRecycler=（RecyclerView）rootView.findViewById（R.id.card\u recycler）；
List dummy=new ArrayList（）；
....
setLayoutManager（新的LinearLayoutManager（MyApplication.getApplicationContext（））；
setAdapter（新的RotaCardAdapter（虚拟））；
返回rootView；
}

将布局逐块分解后，我发现当带有RecyclerView的片段嵌套在ViewPager（android.support.v4.view.ViewPager）中时，会触发onMeasure异常。使用简单的FrameView作为活动布局可避免此问题

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我不把这标记为接下来48小时的可接受的答案——如果你知道为什么，有一个解决办法，或者设法找到一个相关的bug（我没有）报告，请发表它，我会考虑接受你的答案，并从我自己的答案中删除这个评论，谢谢

我刚刚尝试过，不幸的是仍然有同样的问题。