Android学习笔记之RecyclerView

RecyclerView是一种更强大的滚动控件，相比ListView，他不需要使用一些技巧提高运行效率，还能实现横向滚动等优点。

依赖库

因为Google 2018 IO 大会推出了 Android新的扩展库 AndroidX，用于替换原来的 Android扩展库，将原来的android.*替换成androidx.*；只有包名和Maven工件名受到影响，原来的类名，方法名和字段名不会更改，详情看我的上一篇博客Android到Androidx的变迁

在Android 9及之前需要添加以下内容

implementation 'com.android.support:recyclerview-v7:24.2.1'

在Android 10 需要添加

implementation 'androidx.recyclerview:recyclerview:1.1.0'

基本用法

新建一个Fruit类

package com.syc.androidlearning.listViewDemo;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;    }}

修改activity_mian.xml布局文件

<?xml version="1.0" encoding="utf-8"?>

layout中新建fruit_item.xml

<?xml version="1.0" encoding="utf-8"?>

接下来需要为RecyclerView准备一个适配器，新建FruitAdapter类，继承自RecyclerView.Adapter,并将泛型指定为FruitAdapter.ViewHolder。其中，viewholder为fruitadapter中定义的一个内部类。

package com.syc.androidlearning.recyclerView;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 com.syc.androidlearning.R;import com.syc.androidlearning.listViewDemo.Fruit;import java.util.List;public class FruitAdapter extends RecyclerView.Adapter {    private List mFruitList;    static class ViewHolder extends RecyclerView.ViewHolder{        ImageView fruitImage;        TextView fruitName;        public ViewHolder(@NonNull View itemView) {            super(itemView);            fruitImage = itemView.findViewById(R.id.fruit_image);            fruitName = itemView.findViewById(R.id.fruit_name);        }    }    public FruitAdapter(List mFruitList) {        this.mFruitList = mFruitList;    }    @NonNull    @Override    public ViewHolder onCreateViewHolder(@NonNull 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(@NonNull ViewHolder holder, int position) {        Fruit fruit = mFruitList.get(position);        holder.fruitName.setText(fruit.getName());        holder.fruitImage.setImageResource(fruit.getImageId());    }    @Override    public int getItemCount() {        return mFruitList.size();    }}

最后，修改MainActivity中的代码

package com.syc.androidlearning;import androidx.appcompat.app.ActionBar;import androidx.appcompat.app.AppCompatActivity;import androidx.recyclerview.widget.LinearLayoutManager;import androidx.recyclerview.widget.RecyclerView;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.widget.AdapterView;import android.widget.ArrayAdapter;import android.widget.Button;import android.widget.ListView;import android.widget.Toast;import com.syc.androidlearning.listViewDemo.Fruit;import com.syc.androidlearning.recyclerView.FruitAdapter;import java.util.ArrayList;import java.util.List;public class MainActivity extends AppCompatActivity {    private List fruitList = new ArrayList<>();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initFruits();        RecyclerView recyclerView = findViewById(R.id.recycler_view);        LinearLayoutManager layoutManager = new LinearLayoutManager(this);        recyclerView.setLayoutManager(layoutManager);        FruitAdapter fruitAdapter = new FruitAdapter(fruitList);        recyclerView.setAdapter(fruitAdapter);    }    private void initFruits() {        for (int i = 1; i < 10; ++i) {            Fruit apple = new Fruit("apple", R.drawable.ic_launcher_background);            fruitList.add(apple);        }    }}

RecyclerView是一种更强大的滚动控件，相比ListView，他不需要使用一些技巧提高运行效率，还能实现横向滚动等优点。

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