AndroidStudio学习（六)：RecyclerView

程序员文章站 2022-04-20 11:50:17

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新建项目RecyclerViewTest

RecyclerView是新增控件
定义在support库中
需要在app/build.gradle中添加相应的依赖库
运行效率比ListView好很多

ListView只能纵向滚动
RecyclerView可以横向滚动

//build.gradle
dependencies {
    implementation fileTree(dir:'libs',includes: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:30.2.1'
    implementation 'com.android.support:recyclerview-v7:30.2.1'
    testImplementation 'junit:junit:4.12'
}

//activity_main.xml

//添加RecyclerView控件

<?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="match_parent"
    >

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

</LinearLayout>

//新建类Fruit.java

//name表示水果名
//imageId表示水果对应图片的资源id

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 int getImageId(){
        return imageId;
    }
}

//新建布局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="wrap_content">
    
    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        />
    
    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="10dp"
        />

</LinearLayout>

//新建FruitAdapter类

package com.example.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;

import androidx.recyclerview.widget.RecyclerView;

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

    private List<Fruit> mFruitList;

    static class ViewHolder extends RecyclerView.ViewHolder{
        ImageView fruitImage;
        TextView fruitName;

        public ViewHolder(View view){
            super(view);
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView) view.findViewById(R.id.fruit_name);
        }
    }

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

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

    @Override
    public void onBindViewHolder(ViewHolder	holder,	int	position){
        Fruit fruit	= mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }

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

AndroidStudio学习（六)：RecyclerView

//MainActivity

package com.example.recyclerview;

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

import android.os.Bundle;

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);

        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }

    private  void initFruits(){
        for(int i = 0 ; i < 2 ; i++){
            Fruit apple = new Fruit("Apple",R.drawable.apple);
            fruitList.add(apple);
            Fruit banana = new Fruit("Babnana",R.drawable.banana);
            fruitList.add(banana);
            Fruit orange = new Fruit("Orange",R.drawable.orange);
            fruitList.add(orange);
            Fruit watermelon = new Fruit("Watermelon",R.drawable.watermelon);
            fruitList.add(watermelon);
            Fruit pear = new Fruit("Pear",R.drawable.pear);
            fruitList.add(pear);
            Fruit grape = new Fruit("Grape",R.drawable.grape);
            fruitList.add(grape);
            Fruit pineapple = new Fruit("Pineapple",R.drawable.pineapple);
            fruitList.add(pineapple);
            Fruit strawberry = new Fruit("Strawberry",R.drawable.strawberry);
            fruitList.add(strawberry);
            Fruit cherry = new Fruit("Cherry",R.drawable.cherry);
            fruitList.add(cherry);
            Fruit mango = new Fruit("Mango",R.drawable.mango);
            fruitList.add(mango);
        }
    }
}

横向滚动

//修改布局fruit_item.xml

//改成垂直排列
//控件位置改为水平居中
//使用layout_marginTop让文图之间有距离

<?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="wrap_content">
    
    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        />
    
    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="10dp"
        />

</LinearLayout>

//MainActivity

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

        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        
        layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL); //添加一行代码
        
        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }

AndroidStudio学习（六)：RecyclerView

ListView布局排列是由自身去管理的
而RecyclerView将这个工作交给了LayoutManager
LayoutManager制定了一套可扩展的布局排列接口
子类只要按照接口的规范来实现
就能制定出不同的布局排列方式

RecyclerView还提供了网格布局GridLayoutManager和瀑布流布局StaggeredGridLayoutManager。

瀑布流布局StaggeredGridLayoutManager

//修改布局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="match_parent" 
    android:layout_height="wrap_content" 
    android:layout_margin="5dp" > 

    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        />

    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"
        android:layout_marginTop="10dp"
        />

</LinearLayout>

//MainActivity

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);

        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        //LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        //layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);

        //第一个参数指定布局的列数，第二个参数指定布局的排列方向
        StaggeredGridLayoutManager layoutManager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);

        recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }

    //创造一个1-20的随机数，然后将参数中传入的字符串重复随机遍
    private String getRandomLengthName(String name){
        Random random = new Random();
        int length = random.nextInt(20) + 1;
        StringBuilder builder = new StringBuilder();
        for(int i = 0;i < length; i++){
            builder.append(name);
        }
        return builder.toString();
    }

    private  void initFruits(){
        for(int i = 0 ; i < 2 ; i++){
            Fruit apple = new Fruit(getRandomLengthName("Apple"),R.drawable.apple);
            fruitList.add(apple);
            Fruit banana = new Fruit(getRandomLengthName("Babnana"),R.drawable.banana);
            fruitList.add(banana);
            Fruit orange = new Fruit(getRandomLengthName("Orange"),R.drawable.orange);
            fruitList.add(orange);
            Fruit watermelon = new Fruit(getRandomLengthName("Watermelon"),R.drawable.watermelon);
            fruitList.add(watermelon);
            Fruit pear = new Fruit(getRandomLengthName("Pear"),R.drawable.pear);
            fruitList.add(pear);
            Fruit grape = new Fruit(getRandomLengthName("Grape"),R.drawable.grape);
            fruitList.add(grape);
            Fruit pineapple = new Fruit(getRandomLengthName("Pineapple"),R.drawable.pineapple);
            fruitList.add(pineapple);
            Fruit strawberry = new Fruit(getRandomLengthName("Strawberry"),R.drawable.strawberry);
            fruitList.add(strawberry);
            Fruit cherry = new Fruit(getRandomLengthName("Cherry"),R.drawable.cherry);
            fruitList.add(cherry);
            Fruit mango = new Fruit(getRandomLengthName("Mango"),R.drawable.mango);
            fruitList.add(mango);
        }
    }
}

AndroidStudio学习（六)：RecyclerView

点击事件

RecyclerView没有提供类似于setOnItemClickListener()这样的注册监听器方法
而是需要我们自己给子项具体的View去注册点击事件，比ListView复杂
但想点击子项中具体的某一个按钮，ListView就比较麻烦了

//FruitAdapter

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

    private List<Fruit> mFruitList;

    static class ViewHolder extends RecyclerView.ViewHolder{

        View fruitView; //保存子项最外层布局的实例

        ImageView fruitImage;
        TextView fruitName;

        public ViewHolder(View view){
            super(view);

            fruitView = view; //

            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView) view.findViewById(R.id.fruit_name);
        }
    }

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

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent,int viewType){
        View view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.fruit_item,parent,false);
        //ViewHolder holder = new ViewHolder(view);

        final ViewHolder holder = new ViewHolder(view);

        holder.fruitView.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View v){
                int position = holder.getAdapterPosition(); //用户点击的位置
                Fruit fruit = mFruitList.get(position); //Fruit实例
                Toast.makeText(v.getContext(),"You clicked 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 = mFruitList.get(position);
                Toast.makeText(v.getContext(),"You clicked image" + fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });

        return	holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder	holder,	int	position){
        Fruit fruit	= mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }

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

点击图片
AndroidStudio学习（六)：RecyclerView

点击文字
AndroidStudio学习（六)：RecyclerView

AndroidStudio学习（六)：RecyclerView

新建项目RecyclerViewTest

横向滚动

瀑布流布局StaggeredGridLayoutManager

点击事件

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