RecyclerView简单例子演示

Posted 2021-07-27 轻烟散入五侯家

一、首先主活动的xml布局文件activity.xml要这么写

<?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">

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

二、RecyclerView适配器的适配类型（用一个实体类Fruit表示），要这么写

package com.example.magicalpai.recyclerview_view_demo;

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;
    }
}

三、RecyclerView子项我们自己指定的布局fruit_item.xml，要这么写

<?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="274dp"
        android:layout_height="match_parent" />

    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="90dp"
        android:layout_height="match_parent"
        android:layout_gravity="center_vertical"
        android:gravity="center_vertical"
        android:layout_marginLeft="10dp" />
</LinearLayout>

四、RecyclerView适配器FruitAdapter，要这么写`

package com.example.magicalpai.recyclerview_view_demo;

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.recyclerview.widget.RecyclerView;

import com.example.magicalpai.R;

import java.util.List;

//这个FruitAdapter是为RecyclerView准备的一个适配器，它的泛型指定为FruitAdapter.ViewHolder，这个ViewHolder是我们在FruitAdapter中定义的一个内部类
public class FruitAdapter extends RecyclerView.Adapter<FruitAdapter.ViewHolder> {
    private List<Fruit> mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder {
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;
        //ViewHolder的构造函数要传入View参数，这个参数通常就是RecyclerView子项的最外层布局，
        public ViewHolder(View view) {
            super(view);
            fruitView = view;//利用fruitView变量来保存子项最外层布局的实例
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView) view.findViewById(R.id.fruit_name);
        }
    }
    public FruitAdapter(List<Fruit> fruitList) {
        mFruitList = fruitList;
    }

    //这个方法是用来创建ViewHolder实例的
    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        //将fruit_item布局加载进来，然后创建一个ViewHolder实例
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.fruit_item, parent, false);
        final ViewHolder holder = new ViewHolder(view);
        //为最外层布局注册点击事件
        holder.fruitView.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 view " + fruit.getName(),
                        Toast.LENGTH_SHORT).show();
            }
        });
        //为ImageView注册点击事件
        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;
    }
    //这个方法是用于对RecyclerView子项的数据进行赋值的，会在每个子项被滚动到屏幕内的时候执行
    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {  //通过position参数得到当前项的Fruit实例
        Fruit fruit = mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }

    //这个方法用于告诉RecyclerView一共有多少个子项
    @Override
    public int getItemCount() {
        return mFruitList.size();
    }
}

五、主活动的类MainActivity，要这么写`

package com.example.magicalpai.recyclerview_view_demo;

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

import android.os.Bundle;

import com.example.magicalpai.R;

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(); // 初始化水果数据
        RecyclerView recyclerView=(RecyclerView)findViewById(R.id.recycler_view);
        //创建一个LinearLayoutManager对象，可以实现和ListView类似的效果。
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }
     private void initFruits() {
         for (int i = 0; i < 3; i++) {
             Fruit apple = new Fruit("Apple", R.drawable.apple_pic);
             fruitList.add(apple);
             Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
             fruitList.add(banana);
             Fruit watermelon = new Fruit("Watermelon", R.drawable.watermelon_pic);
             fruitList.add(watermelon);
        }
     }
}

六、这样就可以实现以下效果

点击图片的控件，还有相应的提示