Android基础：RecyclerView

介绍

        RecyclerView是Android一个更强大的列表控件,其不仅可以实现和ListView同样的效果,还有优化了ListView中的各种不足。其可以实现数据纵向滚动,也可以实现横向滚动。但是使用RecyclerView需要我们额外导入依赖

简单使用

        1.导入依赖。点击 “Sync Project” 下载一下依赖包。

dependencies {
    implementation 'androidx.recyclerview:recyclerview:1.1.0'
}

代码实现

// MainActivity
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.StaggeredGridLayoutManager;

import android.os.Bundle;
import android.widget.Toast;

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

public class MainActivity extends AppCompatActivity {
    private List<Student> studentList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        // 模拟生成数据
        generateData();

        RecyclerView recyclerView = findViewById(R.id.recycler_view_one);
        /**
         * RecyclerView将布局抽取出来了，所以这边需要给RecyclerView设置布局
         * RecyclerView 支持LinearLayoutManager，GridLayoutManager和StaggeredGridLayoutManager
         */
        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
        linearLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);
        recyclerView.setLayoutManager(linearLayoutManager);

        // 网格显示
//        GridLayoutManager gridLayoutManager= new GridLayoutManager(this,2);
//        recyclerView.setLayoutManager(gridLayoutManager);

        // 瀑布网格方式
        // 构造参数： 一行多少个， 排布方向
//        StaggeredGridLayoutManager staggeredGridLayoutManager =
//                new StaggeredGridLayoutManager(2,LinearLayout.VERTICAL);
//        recyclerView.setLayoutManager(staggeredGridLayoutManager);

        MyAdapter myAdapter = new MyAdapter(studentList,this);
        recyclerView.setAdapter(myAdapter);

        // 点击事件
        myAdapter.setOnRecyclerItemClickListener(new MyAdapter.OnRecyclerItemClickListener() {
            @Override
            public void onRecyclerItemClick(int position) {
                Toast.makeText(getApplicationContext(),"点击了第"+(position+1)+"条",Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void generateData() {
        Random random = new Random();
        for(int i = 0 ;i<100;i++){
            Student student = new Student();
            student.setId((i+1) +"");
            student.setName("测试"+(i+1));
            student.setScore(random.nextInt()+"");
            studentList.add(student);
        }
    }
}

import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

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

import java.util.List;

/**
 * 继承RecyclerView.Adapter<VH>。
 * 这样设计的好处就是强制我们传入优化的方法，避免在开发时忘记优化
 */
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    private List<Student> studentList ;
    private Context context;

    public MyAdapter(List<Student> studentList, Context context) {
        this.studentList = studentList;
        this.context = context;
    }

    /**
     * 用来创建ViewHolder方法的,返回布局的view
     * 然后利用MyViewHolder的构造方法去findViewById()
     *
     * @param parent
     * @param viewType
     * @return
     */
    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = View.inflate(context,R.layout.list_item,null);
        return new MyViewHolder(view);
    }

    /**
     * 将数据绑定到布局上，就是通过这个
     * @param holder
     * @param position
     */
    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.textView_one.setText(studentList.get(position).getId());
        holder.textView_two.setText(studentList.get(position).getName());
        holder.textView_three.setText(studentList.get(position).getScore());
    }

    @Override
    public int getItemCount() {
        return studentList==null?0:studentList.size();
    }

    /**
     * 优化方法:
     * 获取view
     */

    public class MyViewHolder extends RecyclerView.ViewHolder{

        private TextView textView_one;
        private TextView textView_two;
        private TextView textView_three;

        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
            textView_one  = itemView.findViewById(R.id.textView);
            textView_two  = itemView.findViewById(R.id.textView2);
            textView_three  = itemView.findViewById(R.id.textView3);

            // 4.设置监听处理回调方法
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    if (onRecyclerItemClickListener!=null){
                        onRecyclerItemClickListener.onRecyclerItemClick(getAdapterPosition());
                    }
                }
            });

        }
    }

    /**
     * 因为RecyclerView没有提供监听点击事件，所以要自己设置
     * 我们一般在Adapter上设置
     */

    // 2 创建接口对象
     private OnRecyclerItemClickListener onRecyclerItemClickListener;

    // 1.创建接口,给外界实现，然后回调
    public interface OnRecyclerItemClickListener{
        void onRecyclerItemClick(int position);
    }

    // 3。给外部创建一个设置监听的方法
    public void setOnRecyclerItemClickListener(OnRecyclerItemClickListener onRecyclerItemClickListener){
        this.onRecyclerItemClickListener = onRecyclerItemClickListener;
    }
}

public class Student {
    private String id;
    private String name;
    private String score;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getScore() {
        return score;
    }

    public void setScore(String score) {
        this.score = score;
    }
}

<?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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:background="#706B6B"
    android:orientation="vertical"
    tools:context=".MainActivity">

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

<?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="match_parent">


    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="40dp"
        android:text="TextView"
        android:textSize="24sp"
        android:textColor="#535255"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="52dp"
        android:text="TextView"
        android:textSize="32sp"
        android:textColor="#0C0C0C"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toEndOf="@+id/textView"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView"
        android:textSize="20sp"
        android:textColor="#53486A"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/textView2"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>