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java - 片段中 RecyclerView 中的 textView 不显示来自 Java 或 XML 文件的任何文本

问题描述

编辑了我的问题标题我正在尝试将 JSON 数据传递到内置在片段中的 RecyclerView 中，实际上我在装饰 RecyclerView 的 list_items.xml 之前就这样做了。

现在我正在尝试在此 Recycler View 中显示一些普通文本，并且 AS 总是在 MyViewHolder 行给我一个 NullPointerException ...在我评论该行之后，应用程序运行但 RecyclerView 甚至不显示任何文本RecyclerView 的 list_items.xml 中的文本

这是我到目前为止的结果，recyclerView 仅显示 ImageView。并且 textView 不起作用。

在此处输入图像描述

public class MyRecyclerAdapter extends RecyclerView.Adapter<MyRecyclerAdapter.MyViewHolder> {
private Context context; private List<ForumsListItem> forumsListItems;
ForumsFragment fragment=new ForumsFragment();
//Define the constructor for both contenxt and listItem
public MyRecyclerAdapter(Context context, List<ForumsListItem> items) {
    this.context = context;
    forumsListItems =items;

}

@NonNull
@Override
public MyRecyclerAdapter.MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View v= LayoutInflater.from(parent.getContext())
            .inflate(R.layout.forums_listitems,parent,false);

    return new MyViewHolder(v);
}

/*Bind everything from te MyViewHolder*/
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
    //Define listItem position
    ForumsListItem listItem=forumsListItems.get(position);

    //Calling the textView inside bindingViewHolder
    //holder.catListName.setText(listItem.getCatlistName());
    holder.numOfDailyNewPosts.setText(listItem.getNumOftodayPosts());
    holder.descriptTv.setText(listItem.getDescription());
}

@Override
public int getItemCount() {
    return forumsListItems.size();
}

public class MyViewHolder extends RecyclerView.ViewHolder implements  View.OnClickListener{
    private TextView nameTv,descriptTv,numOfDailyNewPosts,catListName;

    private ImageView imgIcons;
    public MyViewHolder(View itemView) {
        super(itemView);
        //things to display in form of List

        descriptTv=(TextView)itemView.findViewById(R.id.item_detail);
        catListName=(TextView)itemView.findViewById(R.id.catListTxt);
        numOfDailyNewPosts=(TextView)itemView.findViewById(R.id.numOfDailyNewPosts);
        //can add Picaso loding images here
        itemView.setOnClickListener(this);
    }
    @Override
    public void onClick(View v){
        int pos=getAdapterPosition();
        //get the current position

        ForumsListItem items= forumsListItems.get(pos);

        Toast.makeText(context,items.getForumsTitles(),Toast.LENGTH_LONG).show();
        //On click functionality

    }
}

}

我的 list_items.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
xmlns:app="http://schemas.android.com/apk/res-auto">

<android.support.v7.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="@dimen/cardview_compat_inset_shadow"
    android:layout_marginTop="5dp"
    android:layout_marginEnd="5dp"
    android:layout_marginStart="5dp"
    android:padding="16dp" >
    <android.support.constraint.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/color_light_yellow">
            <android.support.constraint.ConstraintLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal">
                <ImageView
                    android:id="@+id/forumsTitleImg"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_margin="10dp"
                    app:layout_constraintHorizontal_chainStyle="packed"
                    app:layout_constraintStart_toStartOf="parent"
                    app:layout_constraintTop_toTopOf="parent"
                    android:src="@android:drawable/checkbox_on_background"/>
                <TextView
                    android:id="@+id/numOfDailyNewPosts"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="fdlksfjsdlkjf"
                    app:layout_constraintTop_toTopOf="parent"
                    app:layout_constraintStart_toEndOf="@id/forumsTitleImg"
                    android:layout_margin="10dp" />
            </android.support.constraint.ConstraintLayout>
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/item_detail"
            android:layout_margin="10dp"
            app:layout_constraintTop_toBottomOf="@+id/frame"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent" />
    </android.support.constraint.ConstraintLayout>
</android.support.v7.widget.CardView>

06-03 23:07:30.752 2964-2964/? 我/艺术：后期启用 -Xcheck:jni 06-03 23:07:30.930 2964-2964/com.yamibo.bbs.splashscreen W/艺术：执行失败（/system/bin/dex2oat --runtime-arg -classpath --runtime-arg --debuggable --instruction-set=arm --instruction-set-features=smp,div,atomic_ldrd_strd --runtime-arg -Xrelocate --boot-image=/system/framework/boot.art - -runtime-arg -Xms64m --runtime-arg -Xmx512m --instruction-set-variant=krait --instruction-set-features=default --dex-file=/data/app/com.yamibo.bbs.splashscreen- 2/split_lib_dependencies_apk.apk --oat-file=/data/dalvik-cache/arm/data@app@com.yamibo.bbs.splashscreen-2@split_lib_dependencies_apk.apk@classes.dex) 因为非0退出状态06- 03 23:07:31.416 2964-2964/com.yamibo.bbs.splashscreen W/艺术：闪屏 I/时间线：时间线：Activity_idle id：android.os.BinderProxy@1c32706 时间：11829580 06-03 23:07:36.591 2964-2964/com.yamibo.bbs.splashscreen I/时间线：时间线：Activity_launch_request id:com。 yamibo.bbs.splashscreen 时间：11833307 06-03 23:07:37.435 2964-2964/com.yamibo.bbs.splashscreen D/TEST2: 10 06-03 23:07:37.460 2964-3123/com.yamibo.bbs。 splashscreen W/System：ClassLoader 引用未知路径：/system/framework/tcmclient.jar 06-03 23:07:37.692 2964-2964/com.yamibo.bbs.splashscreen E/RecyclerView：未连接适配器；跳过布局 06-03 23:07:37.773 2964-2964/com.yamibo.bbs.splashscreen I/Choreographer：跳过 40 帧！应用程序可能在其主线程上做了太多工作。06-03 23:07:37.980 2964-2964/com.yamibo.bbs.splashscreen W/art：在 Android 4.1 之前，方法 int android.support.v7。widget.DropDownListView.lookForSelectablePosition(int, boolean) 会错误地覆盖 android.widget.ListView 06-03 23:07:38.084 2964-2964/com.yamibo.bbs.splashscreen E/RecyclerView 中的包私有方法：没有适配器随附的; 跳过布局 06-03 23:07:38.112 2964-2964/com.yamibo.bbs.splashscreen I/Timeline: Timeline: Activity_idle id: android.os.BinderProxy@b5d7e1c time:11834828 06-03 23:07:38.672 2964- 3123/com.yamibo.bbs.splashscreen W/System.err：org.json.JSONException：org.json.JSONArray.get(JSONArray.java:293) 处 org.json.JSONArray.get(JSONArray.java:293) 处的索引 2 超出范围 [0..2)。 json.JSONArray.getJSONObject(JSONArray.java:521) 在 com.yamibo.bbs.splashscreen.ForumsFragment$ForumsJSONParser.doInBackground(ForumsFragment.java:150) 在 com.yamibo.bbs.splashscreen.ForumsFragment$ForumsJSONParser。

标签： javaandroidandroid-layoutandroid-recyclerview

解决方案

@基拉：

请用以下代码替换您的 list_items.xml 文件并再次检查：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v7.widget.CardView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginEnd="5dp"
    android:layout_marginStart="5dp"
    android:layout_marginTop="5dp"
    android:padding="16dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <FrameLayout
            android:id="@+id/frame"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal">

            <LinearLayout
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="horizontal">

                <ImageView
                    android:id="@+id/forumsTitleImg"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_margin="10dp"
                    android:src="@android:drawable/checkbox_on_background" />

                <TextView
                    android:id="@+id/numOfDailyNewPosts"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_margin="10dp"
                    android:text="fdlksfjsdlkjf" />
            </LinearLayout>
        </FrameLayout>

        <TextView
            android:id="@+id/item_detail"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_margin="10dp" />
    </LinearLayout>
</android.support.v7.widget.CardView></RelativeLayout>

这是带有静态数据的 Java 文件：

    public class SampleActivity extends Activity{
    RecyclerView sampleRecycle;
    MyRecyclerAdapter myRecyclerAdapter;
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.sample_activity);

        sampleRecycle = (RecyclerView) findViewById(R.id.sampleRecycle);

        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        sampleRecycle.setLayoutManager(mLayoutManager);
        myRecyclerAdapter = new MyRecyclerAdapter(this);
        sampleRecycle.setAdapter(myRecyclerAdapter);
    }


    public class MyRecyclerAdapter extends RecyclerView.Adapter<MyRecyclerAdapter.MyViewHolder> {
        private Context context;
//        private List<ForumsListItem> forumsListItems;
//        ForumsFragment fragment = new ForumsFragment();

        //Define the constructor for both contenxt and listItem
        public MyRecyclerAdapter(Context context) {
            this.context = context;
//            forumsListItems = items;

        }

        @NonNull
        @Override
        public MyRecyclerAdapter.MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View v = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.list_items, parent, false);

            return new MyViewHolder(v);
        }

        /*Bind everything from te MyViewHolder*/
        @Override
        public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
            //Define listItem position
//            ForumsListItem listItem = forumsListItems.get(position);

            //Calling the textView inside bindingViewHolder
            //holder.catListName.setText(listItem.getCatlistName());
//            holder.numOfDailyNewPosts.setText(listItem.getNumOftodayPosts());
//            holder.descriptTv.setText(listItem.getDescription());
        }

        @Override
        public int getItemCount() {
            return 20;
        }

        public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
            private TextView nameTv, descriptTv, numOfDailyNewPosts, catListName;

            private ImageView imgIcons;

            public MyViewHolder(View itemView) {
                super(itemView);
                //things to display in form of List

                descriptTv = (TextView) itemView.findViewById(R.id.item_detail);
//                catListName = (TextView) itemView.findViewById(R.id.catListTxt);
                numOfDailyNewPosts = (TextView) itemView.findViewById(R.id.numOfDailyNewPosts);
                //can add Picaso loding images here
                itemView.setOnClickListener(this);
            }

            @Override
            public void onClick(View v) {
                int pos = getAdapterPosition();
                //get the current position

//                ForumsListItem items = forumsListItems.get(pos);

//                Toast.makeText(context, items.getForumsTitles(), Toast.LENGTH_LONG).show();
                //On click functionality

            }
        }
    }
}

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