java.lang.NullPointerException at android.support.v7.widget.RecyclerView.onMeasure

Question

I try to use RecyclerView with RecyclerView.Adapter but here is something wrong. I post my code below:

Layout:

   <android.support.v7.widget.RecyclerView     xmlns:tools="http://schemas.android.com/tools"     xmlns:android="http://schemas.android.com/apk/res/android"     android:id="@+id/topic_view"     android:scrollbars="vertical"     android:layout_width="match_parent"     android:layout_height="match_parent" /> 

topic_tile.xml:

<?xml version="1.0" encoding="utf-8"?>  <RelativeLayout     xmlns:android="http://schemas.android.com/apk/res/android"     android:layout_width="match_parent"     android:layout_height="@dimen/tile_height">      <com.makeramen.RoundedImageView         xmlns:app="http://schemas.android.com/apk/res-auto"         android:id="@+id/avatar"         android:padding="16dp"         app:riv_corner_radius="72dp"         android:layout_height="72dp"         android:layout_width="72dp"         />      <LinearLayout         android:id="@+id/text_layout"         android:orientation="vertical"         android:paddingTop="@dimen/text_padding_top_and_bottom"         android:paddingBottom="@dimen/text_padding_top_and_bottom"         android:paddingRight="16dp"         android:layout_width="match_parent"         android:layout_height="match_parent">         <TextView             android:id="@+id/title"             android:textSize="@dimen/primary_font"             android:paddingLeft="@dimen/text_padding_left"             android:textColor="#000000"             android:text="Title"             android:layout_width="match_parent"             android:layout_height="wrap_content"/>         <TextView             android:id="@+id/author"             android:textSize="@dimen/secondary_font"             android:paddingLeft="@dimen/text_padding_left"             android:text="author"             android:layout_width="match_parent"             android:layout_height="wrap_content"/>     </LinearLayout> </RelativeLayout> 

Here is in onCreate()

public class TitleListActivity extends ActionBarActivity {      private RecyclerView topic_view;     private RecyclerView.LayoutManager mLayoutManager;     private TitlelistAdapter adapter;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         setContentView(R.layout.activity_title_list);          .....          topic_view = (RecyclerView)findViewById(R.id.topic_view);         adapter = new TitlelistAdapter(topicList);          topic_view.setHasFixedSize(true);         mLayoutManager = new LinearLayoutManager(TitleListActivity.this);         topic_view.setLayoutManager(mLayoutManager);         topic_view.setItemAnimator(new DefaultItemAnimator());          topic_view.setAdapter(adapter); 

the Adapter:

public class TitlelistAdapter extends RecyclerView.Adapter<TitlelistAdapter.ViewHolder> {      public List<Topic> topicList;      public static class ViewHolder extends RecyclerView.ViewHolder{          TextView title;         TextView author;         RoundedImageView avatar;          public ViewHolder(View itemView) {             super(itemView);              title = (TextView)itemView.findViewById(R.id.title);             author = (TextView)itemView.findViewById(R.id.author);             avatar = (RoundedImageView)itemView.findViewById(R.id.avatar);         }     }      public TitlelistAdapter(List<Topic> topicList){         this.topicList = topicList;     }      @Override     public ViewHolder onCreateViewHolder(ViewGroup viewGroup, int i) {          View itemView = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.topic_tile,viewGroup,false);         return new ViewHolder(itemView);     }      @Override     public void onBindViewHolder(ViewHolder viewHolder, int i) {         viewHolder.title.setText(topicList.get(i).title);         viewHolder.author.setText(topicList.get(i).member.username);     }      @Override     public long getItemId(int position) {         return super.getItemId(position);     }      @Override     public int getItemCount() {         return topicList.size();     } } 

Here is the exception:

java.lang.NullPointerException         at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1694)         at android.view.View.measure(View.java:16497)         at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)         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:16497)         at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)         at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)         at android.view.View.measure(View.java:16497)         at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)         at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453)         at android.view.View.measure(View.java:16497)         at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)         at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)         at android.view.View.measure(View.java:16497)         at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)         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:16497)         at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)         at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)         at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)         at android.view.View.measure(View.java:16497)         at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1912)         at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1109)         at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1291)         at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)         at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600)         at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)         at android.view.Choreographer.doCallbacks(Choreographer.java:574)         at android.view.Choreographer.doFrame(Choreographer.java:544)         at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)         at android.os.Handler.handleCallback(Handler.java:733)         at android.os.Handler.dispatchMessage(Handler.java:95)         at android.os.Looper.loop(Looper.java:136)         at android.app.ActivityThread.main(ActivityThread.java:5001)         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:785)         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)         at dalvik.system.NativeStart.main(Native Method) 

Is it something I didn't init or something I should write more?

Answer 1

I got this error when my RecyclerView had no LayoutManager. Adding this code fixed the problem:

recyclerView.setLayoutManager(new LinearLayoutManager(recyclerView.getContext()));