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();
    }
}

这是一个异常(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)

是我没有初始化的东西还是我应该写更多的东西？

最佳答案

当我的 RecyclerView 没有 LayoutManager 时出现此错误。添加此代码解决了问题:

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

关于android.support.v7.widget.RecyclerView.onMeasure 的 java.lang.NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/26737113/