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

时间：2014-11-04 14:04:44

标签： java android android-recyclerview

我尝试将RecyclerView与RecyclerView.Adapter一起使用，但这里出了点问题。我在下面发布我的代码：

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();
    }
}

以下是例外：

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)

这是我没有初始化的东西还是我应该写的东西？

5 个答案:

答案 0 :(得分：21)

当我的RecyclerView没有LayoutManager时出现此错误。添加此代码修复了问题：

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

答案 1 :(得分：17)

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。从主布局中删除linearLayout，因为它似乎是不必要的。检查您的自定义行布局，即topic_tile以及任何类似错误

<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()

中的

private RecyclerView.LayoutManager mLayoutManager;

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

答案 2 :(得分：11)

如果您在片段内面对RecycleView面临同样的问题，请尝试使用此代码。

@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;
}

答案 3 :(得分：1)

您必须为LayoutManager设置RecycleView：

目前，android支持3种布局。

如果您希望它看似正常ListView，请使用LinearLayoutManager。

如果你想要它似乎是gridView，请使用GridLayoutManager。

如果您希望它看似错开，请使用StaggeredGridLayoutManager

上述3种布局的构造函数

LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getActivity());

GridLayoutManager gridLayoutManager = new GridLayoutManager(getActivity(), 2);

StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(spanCount, StaggeredGridLayoutManager.HORIZONTAL);

然后将LinearLayout设为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库将事件从适配器传递到包含RecycleView的Activity / Fragment。 祝你好运！

答案 4 :(得分：1)

对于任何试图使用ViewPager进行选项卡的人，并且在他们的选项卡中有一个RecyclerView导致这个疯狂的错误，我建议通过创建另一个片段来推迟膨胀，只包括RecylerView。

这个xml文件是我的标签之一，它包含一个框架布局而不是一个回收器。

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将我们的recylcer片段放入其中。

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;
}
}

如您所见，您的FragmentPagerAdapter会调用MostViews进行膨胀，而MostViews本身会调用MasanoryLayout进行膨胀。所以我们转义了FragmentPagerAdapter上下文;）

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