Android学习--RecyclerView使用

     RecyclerView可以说是一个增强版ListView，不仅可以实现和ListView同样的效果，还优化了ListView中存在的各种不足之处。

新建一个项目

1、在build.gradle中添加包依赖(编译环境 SDK API 28)

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    ......
    compile 'com.android.support:recyclerview-v7:28.0.0'
}

2、布局文件activity_main.xml添加RecyclerView

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    tools:context=".MainActivity">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

</LinearLayout>

3、代码中新建一个Fruit、FruitAdapter类

package com.example.recyclerviewtest;

public class Fruit {

    private String name;
    private int imageId;

    public Fruit(String name, int imageId) {
        this.name = name;
        this.imageId = imageId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getImageId() {
        return imageId;
    }

    public void setImageId(int imageId) {
        this.imageId = imageId;
    }
}

fruit_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="100dp">

    <ImageView
        android:layout_width="100dp"
        android:layout_height="80dp"
        android:gravity="center_horizontal"
        android:focusable="true"
        android:id="@+id/image_view"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/text_view"
        android:textSize="20sp"
        android:layout_marginLeft="20dp" />

</LinearLayout>

FruitAdapter类

package com.example.recyclerviewtest;

import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import java.util.List;

public class FruitAdapter extends RecyclerView.Adapter <FruitAdapter.ViewHolder>{

    private List<Fruit> fruitList;

    static class ViewHolder extends RecyclerView.ViewHolder{

        ImageView fruitImage;
        TextView fruitName;

        public ViewHolder(@NonNull View view) {
            super(view);
            fruitImage = view.findViewById(R.id.image_view);
            fruitName = view.findViewById(R.id.text_view);
        }
    }

    public FruitAdapter(List<Fruit> fruitList){
        this.fruitList = fruitList;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.fruit_item, viewGroup, false);
        final ViewHolder holder = new ViewHolder(view);
        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull final ViewHolder viewHolder, int i) {
        Fruit fruit = fruitList.get(i);
        viewHolder.fruitName.setText(fruit.getName());
        viewHolder.fruitImage.setImageResource(fruit.getImageId());
    }

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

}

主MainActivity中

package com.example.recyclerviewtest;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;

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

public class MainActivity extends AppCompatActivity {

    private List<Fruit> fruitList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruit();
        RecyclerView recyclerView = findViewById(R.id.recycler_view);
        //增加显示部分
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(linearLayoutManager);
        FruitAdapter fruitAdapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(fruitAdapter);
    }

    private void initFruit() {
        for (int i = 0; i < 2; i++){
            Fruit apple = new Fruit("apple", R.drawable.apple);
            fruitList.add(apple);
            Fruit pear = new Fruit("pear", R.drawable.pear);
            fruitList.add(pear);
            Fruit grape = new Fruit("grape", R.drawable.grape);
            fruitList.add(grape);
            Fruit orange = new Fruit("orange", R.drawable.orange);
            fruitList.add(orange);
            Fruit pineapple = new Fruit("pineapple", R.drawable.pineapple);
            fruitList.add(pineapple);
            Fruit strawberry = new Fruit("strawberry", R.drawable.strawberry);
            fruitList.add(strawberry);
            Fruit watermelon = new Fruit("watermelon", R.drawable.watermelon);
            fruitList.add(watermelon);
        }
    }
}

运行效果

4、实现横向滚动

修改布局文件fruit_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="100dp"
    android:layout_height="120dp">

    <ImageView
        android:layout_width="100dp"
        android:layout_height="80dp"
        android:gravity="center_horizontal"
        android:focusable="true"
        android:id="@+id/image_view"/>

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/text_view"
        android:textSize="20sp" 
        android:layout_marginTop="10dp"/>

</LinearLayout>

修改MainActivity中

@Override
protected void onCreate(Bundle savedInstanceState) {
    ......
    RecyclerView recyclerView = findViewById(R.id.recycler_view);
    //增加显示部分
    LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
    linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
    recyclerView.setLayoutManager(linearLayoutManager);
    FruitAdapter fruitAdapter = new FruitAdapter(fruitList);
    recyclerView.setAdapter(fruitAdapter);
}

效果图

5、Recyclerview的点击事件

修改FruitAdapter代码

public class FruitAdapter extends RecyclerView.Adapter <FruitAdapter.ViewHolder>{

    private List<Fruit> fruitList;

    static class ViewHolder extends RecyclerView.ViewHolder{

        ImageView fruitImage;
        TextView fruitName;
        View fruitView;

        public ViewHolder(@NonNull View view) {
            super(view);
            fruitView = view;
            fruitImage = view.findViewById(R.id.image_view);
            fruitName = view.findViewById(R.id.text_view);
        }
    }

    public FruitAdapter(List<Fruit> fruitList){
        this.fruitList = fruitList;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.fruit_item, viewGroup, false);
        final ViewHolder holder = new ViewHolder(view);
        holder.fruitView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position = holder.getAdapterPosition();
                Fruit fruit = fruitList.get(position);
                Toast.makeText(v.getContext(), "You click view"+fruit.getName(), Toast.LENGTH_SHORT).show();
            }
        });
        holder.fruitImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int position = holder.getAdapterPosition();
                Fruit fruit = fruitList.get(position);
                Toast.makeText(v.getContext(), "You click image"+fruit.getName(), Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }
......
}

效果图