回收站视图不显示项目

Question

我一直在研究 Java 项目，我需要在其中显示具有不同视图项（图像和文本视图）的多行。 我已经创建了适配器 Class 以及图像和文本设置为文本视图和图像的位置。 但是什么也没有发生，也没有显示任何错误。 以下是我的项目的代码：

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:background="@drawable/ic_bg"
    android:orientation="vertical">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:src="@drawable/ic_action_bar"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:contentDescription="@string/action_bar" />

    <androidx.recyclerview.widget.RecyclerView
        android:background="@color/white"
        android:id="@+id/recylerView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginStart="24dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="24dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/imageView" />


</LinearLayout>

item_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:layout_marginStart="12dp"
    android:layout_marginTop="12dp"
    android:layout_marginEnd="12dp"
    android:orientation="vertical">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/playerRow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="12dp"
        android:layout_marginLeft="12dp"
        android:layout_marginTop="12dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <ImageView
            android:id="@+id/rank"
            android:layout_width="40dp"
            android:layout_height="40dp"
            android:layout_marginStart="4dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            tools:srcCompat="@tools:sample/avatars" />

        <ImageView
            android:id="@+id/player_profile"
            android:layout_width="80dp"
            android:layout_height="80dp"
            android:layout_marginStart="12dp"
            android:layout_marginEnd="24dp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/name"
            app:layout_constraintStart_toEndOf="@+id/rank"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.0"
            tools:srcCompat="@drawable/ic_profile" />

        <TextView
            android:id="@+id/player_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="36dp"
            android:layout_marginTop="16dp"
            android:text="@string/player_s_name"
            android:textColor="#F8BF2A"
            android:textSize="10sp"
            app:layout_constraintEnd_toStartOf="@+id/arrow"
            app:layout_constraintHorizontal_bias="0.0"
            app:layout_constraintStart_toEndOf="@+id/player_profile"
            app:layout_constraintTop_toTopOf="parent"
            tools:ignore="SmallSp" />

        <TextView
            android:id="@+id/name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="16dp"
            android:layout_marginBottom="23dp"
            android:text="@string/player_s_name"
            android:textColor="@color/white"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/arrow"
            app:layout_constraintStart_toEndOf="@+id/player_profile"
            app:layout_constraintTop_toBottomOf="@+id/player_name"
            app:layout_constraintVertical_bias="1.0" />

        <ImageView
            android:id="@+id/arrow"
            android:layout_width="20dp"
            android:layout_height="wrap_content"
            android:layout_marginStart="27dp"
            android:layout_marginTop="30dp"
            android:layout_marginBottom="25dp"
            android:contentDescription="arrow"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toEndOf="@+id/name"
            app:layout_constraintTop_toTopOf="parent"
            app:srcCompat="@drawable/ic_arrow" />

        <TextView
            android:id="@+id/score_id"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="48dp"
            android:layout_marginTop="16dp"
            android:text="@string/score"
            android:textColor="#F8BF2A"
            android:textSize="10sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.0"
            app:layout_constraintStart_toEndOf="@+id/arrow"
            app:layout_constraintTop_toTopOf="parent"
            tools:ignore="SmallSp" />

        <TextView
            android:id="@+id/total_score"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginStart="36dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="32dp"
            android:layout_marginBottom="23dp"
            android:text="@string/gained"
            android:textColor="@color/white"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@+id/arrow"
            app:layout_constraintTop_toBottomOf="@+id/score_id" />


    </androidx.constraintlayout.widget.ConstraintLayout>

    <View
        android:id="@+id/divider"
        android:layout_width="match_parent"
        android:layout_height="5dp"
        android:background="#FFFFFF" />

    <View
        android:id="@+id/divider2"
        android:layout_width="match_parent"
        android:layout_height="3dp"
        android:layout_marginBottom="640dp"
        android:background="#7F4242"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/divider" />
</LinearLayout>

主要活动.java

package com.example.leaderboard;

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

import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        String[] playerNames = {"Alex Wingates", "Wolfe", "Queens", "Adrian Oz", "Timber", "Timber", "Timber", "Timber", "Timber"};
        String[] scores = {"12540","10,706","9,283","9,336","5,124","5,124","5,124","5,124","5,124"};
        int[] ranks={R.drawable.ic_one, R.drawable.ic_two, R.drawable.ic_three, R.drawable.ic_four, R.drawable.ic_five,
                R.drawable.ic_five, R.drawable.ic_five, R.drawable.ic_five, R.drawable.ic_five};
        RecyclerView recyclerView;
        RecyclerView.Adapter mAdapter;
        RecyclerView.LayoutManager layoutManager;
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        getSupportActionBar().hide();
        recyclerView=findViewById(R.id.recylerView);
        //setting layout

        layoutManager= new LinearLayoutManager(this);
        mAdapter = new ProgramAdapter(this, playerNames, scores, ranks);
        // Finally, attach the adapter with the RecyclerView
        recyclerView.setAdapter(mAdapter);



    }
}

程序适配器.java

package com.example.leaderboard;

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

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

public class ProgramAdapter extends RecyclerView.Adapter<ProgramAdapter.ViewHolder> {
    Context context;
    String[] programNameList;
    String[] programDescriptionList;
    int[] images;

    // Create a static inner class and provide references to all the Views for each data item.
    // This is particularly useful for caching the Views within the item layout for fast access.
    public static class ViewHolder extends RecyclerView.ViewHolder{
        // Declare member variables for all the Views in a row
        TextView rowName;
        TextView rowDescription;
        ImageView rowImage;
        // Create a constructor that accepts the entire row and search the View hierarchy to find each subview
        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            // Store the item subviews in member variables
            rowName = itemView.findViewById(R.id.name);
            rowDescription = itemView.findViewById(R.id.total_score);
            rowImage = itemView.findViewById(R.id.rank);
        }
    }
    // Provide a suitable constructor
    public ProgramAdapter(Context context, String[] programNameList, String[] programDescriptionList, int[] images){
        // Initialize the class scope variables with values received from constructor
        this.context = context;
        this.programNameList = programNameList;
        this.programDescriptionList = programDescriptionList;
        this.images = images;
    }

    // Create new views to be invoked by the layout manager
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // Create a LayoutInflater object
        LayoutInflater inflater = LayoutInflater.from(context);
        // Inflate the custom layout
        View view = inflater.inflate(R.layout.item_layout, parent, false);
        // To attach OnClickListener
        view.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                TextView rowName = v.findViewById(R.id.player_name);
                Toast.makeText(context, "Clicked Item: " + rowName.getText().toString(), Toast.LENGTH_SHORT).show();
            }
        });
        // Return a new holder instance
        ViewHolder viewHolder = new ViewHolder(view);
        return viewHolder;
    }

    // Replace the contents of a view to be invoked by the layout manager
    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        // Get element from your dataset at this position and replace the contents of the View with that element
        holder.rowName.setText(programNameList[position]);
        holder.rowDescription.setText(programDescriptionList[position]);
        holder.rowImage.setImageResource(images[position]);
    }

    // Return the size of your dataset
    @Override
    public int getItemCount() {
        return programNameList.length;
    }
}

Answer 1

我运行了您的代码，发现您没有显示任何内容，因为您没有将布局管理器设置为 recyclerView。

recyclerView.setLayoutManager(layoutManager);

Answer 2

在主要活动中。java:-

recyclerView.setLayoutManager(layoutManager);

在 item_layout.xml 中：-

在最后一个视图中，移除 layout_marginBottom

如果问题仍未解决，请将您的代码推送到 github 并将 email“mdfaiz027@gmail.com”的链接发送给我。

我会尽力帮助你。