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

我尝试用RecyclerView.Adapter使用RecyclerView,但是这里有错误。 我发布我的代码如下:

布局:

<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> 

这里是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); 

适配器:

 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(); } } 

这是一个例外:

 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) 

是我没有启动的东西,还是我应该写更多的东西?

Solutions Collecting From Web of "java.lang.NullPointerException在android.support.v7.widget.RecyclerView.onMeasure"

当我的RecyclerView没有LayoutManager时,我得到了这个错误。 添加这个代码解决了这个问题:

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

你的xml显示你有两个android命名空间,实际上应该给你一个错误,因为在android中你只能使用命名空间一次。 从主布局中移除linearLayout,因为看起来没有必要。 检查您的自定义行布局即topic_tile以及任何类似的错误

 <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" /> 

编辑:

onCreate()

 private RecyclerView.LayoutManager mLayoutManager; @Override protected void onCreate(Bundle savedInstanceState) { . . . mLayoutManager = new LinearLayoutManager(this); recycleView.setLayoutManager(mLayoutManager); } 

如果你的RecycleView面临同样的问题,请尝试使用这段代码。

 @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { // Inflate the layout for this fragment View rootView = inflater.inflate(R.layout.fragment_latest, container, false); // get recycler view mRecyclerView = (RecyclerView) rootView.findViewById(R.id.novel_item_list); //mRecyclerView.setHasFixedSize(true); // use a linear layout manager mLayoutManager = new LinearLayoutManager(getActivity()); mRecyclerView.setLayoutManager(mLayoutManager); String[] abc = {"hi","how are you","this is recycler"}; // specify an adapter (see also next example) mAdapter = new RecyclerViewAdapter(abc); mRecyclerView.setAdapter(mAdapter); return rootView; } 

您必须为RecycleView设置LayoutManager

目前,android支持3种布局。

如果你想看起来像一个正常的ListView ,使用LinearLayoutManager

如果你想看起来像一个gridView,使用GridLayoutManager

如果你想看起来错开了,使用StaggeredGridLayoutManager

上面3种布局的构造器

 LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity()); GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(), 2); StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(spanCount, StaggeredGridLayoutManager.HORIZONTAL); 

然后你将LinearLayout设置为RecycleView (在这种情况下,我使用了LinearLayoutManager

 recyclerView = (RecyclerView) view.findViewById(R.id.saved_recycle_view); recyclerView.setHasFixedSize(true); LinearLayoutManager linearLayoutManager = new LinearLayoutManager(context); recyclerView.setLayoutManager(linearLayoutManager); 

无论如何,使用OttoBus库将事件从Adapter传递到包含RecycleView Activity / Fragment。 祝你好运 !

对于任何人试图使用ViewPager的标签,并在其选项卡内有一个RecyclerView导致这个疯狂的错误,我build议通过创build另一个片段,只包括RecylerView推迟膨胀。

这个XML文件是我的标签之一,其中包含一个框架布局,而不是一个回收站。

shop_most_views_fragment.xml

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <FrameLayout android:id="@+id/most_view_item_frameLayout" android:layout_width="match_parent" android:layout_height="match_parent" android:background="#f3f3f3" /> </LinearLayout> 

它的java类

 public class MostViews extends Fragment { private String title; private int page; View convertedView; RecyclerView grids; public static MostViews newInstance(int page, String title) { MostViews fragmentFirst = new MostViews(); Bundle args = new Bundle(); args.putInt("someInt", page); args.putString("someTitle", title); fragmentFirst.setArguments(args); return fragmentFirst; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); page = getArguments().getInt("someInt", 0); title = getArguments().getString("someTitle"); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { convertedView = inflater.inflate(R.layout.shop_most_views_fragment, container, false); transitMasonaryLayoutFragmentIntoFramLayout(); return convertedView; } private void transitMasonaryLayoutFragmentIntoFramLayout() { MasanoryLayout masanoryLayout = new MasanoryLayout(); FragmentManager fragmentManager = getActivity().getSupportFragmentManager(); fragmentManager.beginTransaction() .add(R.id.most_view_item_frameLayout, masanoryLayout).commit(); } } 

所以我们有一个框架布局,把我们的recylcer片段。

shop_most_view_masanory_fragment.xml

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="match_parent" android:layout_height="match_parent"> <android.support.v7.widget.RecyclerView android:id="@+id/mostViewsItem" android:layout_width="match_parent" android:layout_height="match_parent" /> </LinearLayout> 

它的java类

 public class MasanoryLayout extends Fragment { View convertedView; RecyclerView grids; @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { convertedView = inflater.inflate(R.layout.shop_most_view_masanory_fragment, container, false); grids = (RecyclerView) convertedView.findViewById(R.id.mostViewsItem); setLayoutManagerOnRecyclerView(); MasonryAdapter adapter = new MasonryAdapter(initializeData()); grids.setAdapter(adapter); return convertedView; } private void setLayoutManagerOnRecyclerView() { grids.setLayoutManager(new StaggeredGridLayoutManager(3, StaggeredGridLayoutManager.VERTICAL)); } private List<StoreItem> initializeData() { List<StoreItem> storeItems = new ArrayList<>(); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.detailed_index_store)); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.clothstore)); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.detailed_index_store)); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.clothstore)); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.detailed_index_store)); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.detailed_index_store)); storeItems.add(new StoreItem("احسان", "احسان", R.drawable.clothstore)); return storeItems; } } 

正如你看到你的FragmentPagerAdapter会调用MostViews被夸大和MostViews本身会调用MasanoryLayout被夸大。 所以我们逃脱了FragmentPagerAdapter的上下文;)