Аварии RecyclerView

Question

Я создаю фрагмент и читаю sqlite и предположим, чтобы заполнить данные на экране. Но приложение падает со следующей ошибкой.

FATAL EXCEPTION: main 
      Process: uk.ac.gre.facilitiesreviewapp, PID: 6249 
      java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$LayoutManager.onMeasure(android.support.v7.widget.RecyclerView$Recycler, android.support.v7.widget.RecyclerView$State, int, int)' on a null object reference 
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764) 
        at android.view.View.measure(View.java:17536) 
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727) 
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463) 
        at android.view.View.measure(View.java:17536) 
        at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1456) 
        at android.view.View.measure(View.java:17536) 
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5478) 
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
        at android.view.View.measure(View.java:17536) 
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5478) 
        at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453) 
        at android.view.View.measure(View.java:17536) 
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5478) 
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
        at android.view.View.measure(View.java:17536) 
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5478) 
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
        at android.view.View.measure(View.java:17536) 
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5478) 
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2629) 
        at android.view.View.measure(View.java:17536) 
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2102) 
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1218) 
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1435) 
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1106) 
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6018) 
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:792) 
        at android.view.Choreographer.doCallbacks(Choreographer.java:596) 
        at android.view.Choreographer.doFrame(Choreographer.java:557) 
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:778) 
        at android.os.Handler.handleCallback(Handler.java:739) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:155) 
        at android.app.ActivityThread.main(ActivityThread.java:5696) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at java.lang.reflect.Method.invoke(Method.java:372) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1028) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823) 

Я знаю эту ошибку, предполагает, чтобы произойти, если у меня нет layoutmanager набора к Recyclerview, но я сделал это, как вы можете увидеть в приведенном ниже класс.

Класс

public class WifiFragment extends Fragment { 
    ReviewsDataSource mReviewsDataSource; 
    List<Review> mReviews; 
    private RecyclerView mRecyclerView; 
    private RecyclerView.Adapter mAdapter; 
    private RecyclerView.LayoutManager mLayoutManager; 

    public WifiFragment() { 
    } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 

     View rootView = inflater.inflate(R.layout.fragment_review_list, container, false); 
     mRecyclerView = (RecyclerView) rootView.findViewById(R.id.review_recycler_view); 

     return rootView; 
    } 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 
     mReviewsDataSource = new ReviewsDataSource(getActivity()); 
     mLayoutManager = new LinearLayoutManager(getActivity()); 
     mRecyclerView.setLayoutManager(mLayoutManager); 
     mRecyclerView.setItemAnimator(new DefaultItemAnimator()); 

     try { 
      mReviewsDataSource.open(); 
      mReviews = mReviewsDataSource.getAllReviewsByFacility(getActivity().getString(R.string.title_section1)); 
      mAdapter = new ReviewAdapter(mReviews); 
      mRecyclerView.setAdapter(mAdapter); 
      Toast.makeText(getActivity(), String.valueOf(mReviews.size()), Toast.LENGTH_SHORT).show(); 
      Log.v(getActivity().getString(R.string.title_section1), String.valueOf(mReviews.size())); 
     } catch (SQLException e) { 
      e.printStackTrace(); 
     } 
    } 
} 

XML

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" 
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin" 
    android:paddingRight="@dimen/activity_horizontal_margin" 
    android:paddingTop="@dimen/activity_vertical_margin" 
    android:paddingBottom="@dimen/activity_vertical_margin" 
    tools:context="uk.ac.gre.facilitiesreviewapp.ReviewList$PlaceholderFragment"> 

    <!-- A RecyclerView with some commonly used attributes --> 
    <android.support.v7.widget.RecyclerView 
     android:id="@+id/review_recycler_view" 
     android:foreground="?selectableItemBackground" 
     android:scrollbars="vertical" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent"/> 

</RelativeLayout> 

Я переместил раздел LayoutManager от onCreateView до onActivityCreated, как не предлагается в некоторых ответах, но до сих пор никакой помощи. Любая идея, почему это происходит?

Answer 1

Возможно, это связано с тем, что RecylerView не был реализован во фрагментах, которые используют один и тот же файл макета. У меня тоже была эта проблема.