简单的 Recyclerview 不在屏幕上显示任何内容

Question

我正在尝试创建回收站视图，但我的 Android 屏幕上没有显示任何内容。我一直在调试，我不确定我显示视图的方式是否有问题。任何帮助将不胜感激。

下面是我的 MainActivitiy，应该显示列表的地方

package com.example.flavechallenge;

import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;


public class MainActivity extends AppCompatActivity {

    RecyclerView recyclerView;
    String [] s1;
    String [] s2;



    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        s1 = getResources().getStringArray(R.array.names);
        s2 = getResources().getStringArray(R.array.description);

        recyclerView = findViewById(R.id.recyclerView);

        MyAdapter myAdapter = new MyAdapter(this, s1, s2);
        
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(myAdapter);

    }
}

下面是MainActivity对应的xml文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <com.google.android.material.appbar.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/Theme.FlaveChallenge.AppBarOverlay">

        <androidx.appcompat.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/Theme.FlaveChallenge.PopupOverlay" />

    </com.google.android.material.appbar.AppBarLayout>


    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:srcCompat="@android:drawable/ic_dialog_email" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recyclerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

最后，这里是我的回收站视图的适配器

package com.example.flavechallenge;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    String[] data1;
    String [] data2;
    Context context;

    public MyAdapter(Context ct, String [] s1, String[] s2) {
        context = ct;
        data1 = s1;
        data2 = s2;
    }

    @NonNull
    @org.jetbrains.annotations.NotNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull @org.jetbrains.annotations.NotNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(context);
        View view = inflater.inflate(R.layout.my_row, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull @org.jetbrains.annotations.NotNull MyAdapter.MyViewHolder holder, int position) {
        holder.myText1.setText(data1[position]);
        holder.myText2.setText(data2[position]);
    }

    @Override
    public int getItemCount() {
        return data1.length;
    }

    public static class MyViewHolder extends RecyclerView.ViewHolder {

        TextView myText1;
        TextView myText2;

        public MyViewHolder(@NonNull @org.jetbrains.annotations.NotNull View itemView) {
            super(itemView);
            myText1 = itemView.findViewById(R.id.myText1Id);
            myText2 = itemView.findViewById(R.id.myText2Id);
        }
    }
}

另外，我还有一个 my_row.xml 文件，描述了 RecyclerView 中单行的显示

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto">

    <androidx.cardview.widget.CardView
        android:layout_width="409dp"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.054">

        <TextView
            android:id="@+id/myText1Id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="TextView" />

        <TextView
            android:id="@+id/myText2Id"
            android:layout_width="97dp"
            android:layout_height="match_parent"
            android:text="TextView Again" />
    </androidx.cardview.widget.CardView>
</androidx.constraintlayout.widget.ConstraintLayout>

最后，为了清楚起见，我想在回收站视图中显示的项目在下面的strings.xml、名称和描述中找到

<resources>
    <string name="app_name">FlaveChallenge</string>
    <string name="title_activity_main">MainActivity</string>
    <!-- Strings used for fragments for navigation -->
    <string name="first_fragment_label">First Fragment</string>
    <string name="second_fragment_label">Second Fragment</string>
    <string name="next">Next</string>
    <string name="previous">Previous</string>

    <string name="hello_first_fragment">Hello first fragment</string>
    <string name="hello_second_fragment">Hello second fragment. Arg: %1$s</string>

    <string-array name="names">
        <item>item 1</item>
        <item>item 2</item>
        <item>item 3</item>
    </string-array>

    <string-array name="description">
        <item>description 1</item>
        <item>description 2</item>
        <item>description 3</item>
    </string-array>
</resources>

感谢您的帮助！

Answer 1

将此行添加到 xml 中的 RecyclerView：

app:layout_behavior="@string/appbar_scrolling_view_behavior"

将my_row.xml的ConstraintLayout中的layout_height从match_parent更改为wrap_content

Answer 2

你必须添加一个布局管理器