RecyclerView

RecyclerView 是 Android 中一个用于高效展示大量列表数据的强大控件，是 ListView 的升级版。它具有更好的性能、更灵活的布局管理方式，并且支持强大的扩展能力。

RecyclerView 会回收这些独立的元素。当某个 item 滚出屏幕时，RecyclerView 不会销毁它对应的视图；相反，RecyclerView 会复用该视图来展示新滚入屏幕的 item。

创建步骤

1. Item 布局

一个 XML 布局文件，用于定义 RecyclerView 中 单个列表项（item） 的界面布局。

2. RecyclerView

在 Activity 中创建 RecyclerView 并对其进行初始化。

3. 模型类

表示用于保存 RecyclerView 每个条目信息的数据结构。

4. 适配器类

包含所有与 RecyclerView 实现相关的方法（创建、绑定以及确定条目数量）。

5. ViewHolder

保存每个条目布局中视图的引用，用于优化视图查找效率。

代码示例

Item 布局

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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="wrap_content">

    <ImageView
        android:id="@+id/image_view"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:layout_marginTop="16dp"
        android:layout_marginStart="16dp"
        android:background="@drawable/ic_launcher_background"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/title_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:textColor="@color/white"
        android:text="title"
        android:textSize="32sp"
        app:layout_constraintStart_toEndOf="@+id/image_view"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/description_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="16dp"
        android:text="Your description here"
        android:textColor="@color/white"
        android:textSize="16sp"
        app:layout_constraintStart_toEndOf="@+id/image_view"
        app:layout_constraintTop_toBottomOf="@+id/title_view" />
</androidx.constraintlayout.widget.ConstraintLayout>

RecyclerView

布局文件中的代码

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#283330"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/header_image"
        android:layout_width="0dp"
        android:layout_height="230dp"
        android:src="@drawable/header"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginTop="24dp"
        android:background="#283330"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/header_image" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity 中的代码

package com.stewednoodles.marketapp;

import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;

import androidx.activity.EdgeToEdge;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.AbstractList;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements ItemClickListener {
    // 1. AdapterView
    RecyclerView mRecyclerView;

    // 2. Data source
    List<Item> mItems;

    // 3. Adapter
    ItemAdapter itemAdapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });

        // Adapterview
        mRecyclerView = findViewById(R.id.recycler_view);

        mItems = new ArrayList<>();
        mItems.add(new Item(R.drawable.fruit, "Fruits", "Fresh Fruits from the Garden."));
        mItems.add(new Item(R.drawable.beverage, "Beverages", "Beverages from the Bottle."));
        mItems.add(new Item(R.drawable.bread, "Bread", "Bread from the Bread Factory."));
        mItems.add(new Item(R.drawable.milk, "Milk", "Milk from the Milk Factory."));
        mItems.add(new Item(R.drawable.popcorn, "Popcorn", "Popcorn from the Popcorn Factory."));
        mItems.add(new Item(R.drawable.vegitables, "Vegitables", "Vegitables from the Vegitables Factory."));
        mItems.add(new Item(R.drawable.fruit, "Fruits", "Fresh Fruits from the Garden."));
        mItems.add(new Item(R.drawable.beverage, "Beverages", "Beverages from the Bottle."));
        mItems.add(new Item(R.drawable.bread, "Bread", "Bread from the Bread Factory."));
        mItems.add(new Item(R.drawable.milk, "Milk", "Milk from the Milk Factory."));
        mItems.add(new Item(R.drawable.popcorn, "Popcorn", "Popcorn from the Popcorn Factory."));
        mItems.add(new Item(R.drawable.vegitables, "Vegitables", "Vegitables from the Vegitables Factory."));

        // 设置 mRecyclerView 的线性布局
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(layoutManager);

        itemAdapter = new ItemAdapter(mItems);
        mRecyclerView.setAdapter(itemAdapter);

        itemAdapter.setClickListener(this);
    }

    @Override
    public void onClick(View v, int pos) {
        Toast.makeText(this, "You choose: " + mItems.get(pos).getItemName(), Toast.LENGTH_SHORT).show();
    }
}

接口代码

package com.stewednoodles.marketapp;

import android.view.View;

public interface ItemClickListener {
    void onClick(View v, int pos);
}

模型类

模型类的相关代码

package com.stewednoodles.marketapp;

public class Item {
    private int itemImg;
    private String itemName;
    private String itemDesc;

    public Item(int itemImg, String itemName, String itemDesc) {
        this.itemImg = itemImg;
        this.itemName = itemName;
        this.itemDesc = itemDesc;
    }

    public int getItemImg() {
        return itemImg;
    }

    public void setItemImg(int itemImg) {
        this.itemImg = itemImg;
    }

    public String getItemName() {
        return itemName;
    }

    public void setItemName(String itemName) {
        this.itemName = itemName;
    }

    public String getItemDesc() {
        return itemDesc;
    }

    public void setItemDesc(String itemDesc) {
        this.itemDesc = itemDesc;
    }
}

适配器类以及ViewHolder

适配器类以及ViewHolder的相关代码

package com.stewednoodles.marketapp;

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

import java.util.List;

public class ItemAdapter extends RecyclerView.Adapter<ItemAdapter.ItemViewHolder> {
    private List<Item> mItems;

    public ItemClickListener mItemClickListener;

    public void setClickListener(ItemClickListener listener) {
        this.mItemClickListener = listener;
    }

    public ItemAdapter(List<Item> mItems) {
        this.mItems = mItems;
    }

    /**
     * 负责为items创建新的viewholder
     */
    @NonNull
    @Override
    public ItemViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater
                .from(parent.getContext())
                .inflate(R.layout.item_layout, parent, false);
        return new ItemViewHolder(itemView);
    }

    /**
     * 将数据源中的数据绑定到viewholder中的views上
     */
    @Override
    public void onBindViewHolder(@NonNull ItemViewHolder holder, int position) {
        Item item = mItems.get(position);
        holder.itemImageView.setImageResource(item.getItemImg());
        holder.itemNameView.setText(item.getItemName());
        holder.itemDescView.setText(item.getItemDesc());
    }

    /**
     * 返回数据源的长度
     */
    @Override
    public int getItemCount() {
        return mItems.size();
    }

    /**
     * 提供你所使用视图类型的引用（自定义 ViewHolder）。
     */
    public class ItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        ImageView itemImageView;
        TextView itemNameView;
        TextView itemDescView;

        public ItemViewHolder(@NonNull View itemView) {
            super(itemView);
            itemImageView = itemView.findViewById(R.id.image_view);
            itemNameView = itemView.findViewById(R.id.title_view);
            itemDescView = itemView.findViewById(R.id.description_view);

            itemView.setOnClickListener(this);
        }

        @Override
        public void onClick(View v) {
            if (mItemClickListener != null) {
                mItemClickListener.onClick(v, getAdapterPosition());
            }
        }
    }
}

运行效果

运行的效果图，如下所示