APP学习6（RecycleView）

1. RecycleView

Android5.0之后提供的用于在有限的窗口范围内显示大量数据的控件。

与ListView相比，展示效果、适配器更好。

代码：

activity_main.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="match_parent"
    android:orientation="vertical"
    >
    <androidx.recyclerview.widget.RecyclerView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/mylist"
        ></androidx.recyclerview.widget.RecyclerView>

</LinearLayout>

itemlayout.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="match_parent"
    android:padding="10dp"
    android:gravity="center"
    android:orientation="horizontal"
    >
   <ImageView
       android:layout_width="120dp"
       android:layout_height="100dp"
       android:id="@+id/iv"
       ></ImageView>


    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/title"
            android:text="标题"
            android:layout_marginLeft="20dp"
            android:textColor="@color/black"
            android:textSize="25sp"></TextView>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/info"
            android:text="详细信息"
            android:layout_marginTop="5dp"
            android:maxLines="2"
            android:layout_marginLeft="20dp"
            android:layout_below="@+id/title"
            android:textColor="@color/black"
            android:ellipsize="end"
            android:textSize="20sp"></TextView>
    </RelativeLayout>
</LinearLayout>

MainActivity.java

package com.example.myapp;

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

import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
/*
* 1.获取recycleview的控件对象
* 2.设置recycleview控件的适配器，包括item视图的布局和数据内容都要在适配器中定义出来
* 3.设置recycleview的布局管理器
* 4.创建适配器对象，将此对象交给recycleview控件对象
* */
    //1.
    private RecyclerView mylist;
    private String[] title={"苹果","草莓","西瓜","水蜜桃"};
    private int[] imgs={R.drawable.apple,R.drawable.straw,R.drawable.water,R.drawable.mitao};
    private String[] info={"苹果时红色的","草莓是草莓","西瓜是西瓜","水蜜桃是粉色的"};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mylist = findViewById(R.id.mylist);
        //3.设置布局管理器
        mylist.setLayoutManager(new LinearLayoutManager(MainActivity.this,LinearLayoutManager.VERTICAL,true));
        //4.适配器
        MyAdapter ma = new MyAdapter();
        mylist.setAdapter(ma);
    }
    class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyHolder>{

        @NonNull
        @Override//作用：获取itemview的视图对象，并将视图对象传递给viewholder
        public MyHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View v1 = View.inflate(MainActivity.this,R.layout.itemlayout,null);
            MyHolder myHolder = new MyHolder(v1);
            return myHolder;
        }

        @Override//onBindViewHolder将值绑定给hold对象
        public void onBindViewHolder(@NonNull MyHolder holder, int position) {
            holder.info.setText(info[position]);
            holder.title.setText(title[position]);
            holder.iv.setBackgroundResource(imgs[position]);
        }

        @Override
        public int getItemCount() {
            return title.length;
        }

        class MyHolder extends RecyclerView.ViewHolder{
            //需要赋值的控件对象
            ImageView iv;
            TextView title,info;
            public MyHolder(@NonNull View itemView) {
                super(itemView);
                iv = itemView.findViewById(R.id.iv);
                title = itemView.findViewById(R.id.title);
                info = itemView.findViewById(R.id.info);

            }
        }
    }

}

这种方式特别方便，也需要多理解。