概念

Adapter(适配器)，是Android开发必不可少的一个知识点，它负责连接控件与数据源，将数据绑定到控件上。比如经常使用的ListView(列表视图)、网格视图(GridView)、Spinner(下拉列表)等都需要用到适配器进行数据显示，也是比较灵活的功能，下面介绍常用的两种适配器:

ArrayAdapter

ArrayAdapter(数组适配器),最为基础简单的适配器，只能显示一行文字

实例:

1、布局文件
在布局文件中只加入了加入<ListView>控件

<?xml version="1.0" encoding="utf-8"?>  <LinearLayout xmlns:android="https://schemas.android.com/apk/res/android"      xmlns:app="https://schemas.android.com/apk/res-auto"      xmlns:tools="https://schemas.android.com/tools"      android:layout_width="match_parent"      android:layout_height="match_parent"      tools:context=".MainActivity"      android:orientation="vertical">     <ListView         android:id="@+id/lv_test"         android:layout_width="match_parent"         android:layout_height="match_parent"/>  </LinearLayout> 

2、java代码

ArrayAdapter(this, android.R.layout.simple_list_item_1, Data); 

第一个参数是上下文对象
第二个参数是显示的item的样式，android已经定义好，可直接使用，也可使用自定义的TextView
item的样式:
simple_list_item_1:单独的一行文本框
simple_list_item_2:有两个文本框组成
simple_list_item_checked每项都是由一个已选中的列表项
simple_list_item_multiple_choice:都带有一个复选框
simple_list_item_single_choice：都带有一个单选框
第三个参数是要显示的数据

package com.example.application;  import androidx.appcompat.app.AppCompatActivity;  import android.os.Bundle;  import android.widget.ArrayAdapter;  import android.widget.ListView;  public class MainActivity extends AppCompatActivity {      ListView lvTest;      @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          lvTest = findViewById(R.id.lv_test);          String Data[] = {"1", "2", "3","4","5","6","7", "8", "9","10","11","12","13", "14", "15","16","17","18"}; //显示的数据不一定是String也可以是List集合          ArrayAdapter adapter = new ArrayAdapter(this, android.R.layout.simple_list_item_1, Data);        //创建数组适配器          lvTest.setAdapter(adapter);                          //setAdapter方法添加适配器      }  } 

3、效果图

BaseAdapter

BaseAdapter最常用的适配器
具体看代码及解析，注意看各控件的id，方便理清思路:

activity_main.xml:
就有一个ListView 并为其设置ID为list_info

<?xml version="1.0" encoding="utf-8"?>  <RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"  xmlns:app="https://schemas.android.com/apk/res-auto"  xmlns:tools="https://schemas.android.com/tools"  android:layout_width="match_parent"  android:layout_height="wrap_content"  tools:context=".MainActivity"      >  <ListView      android:id="@+id/list_info"      android:layout_width="match_parent"      android:layout_height="match_parent"/>  </RelativeLayout> 

activity_i.xm:
给控件加上ID并设置样式

<?xml version="1.0" encoding="utf-8"?>  <RelativeLayout xmlns:android="https://schemas.android.com/apk/res/android"      xmlns:app="https://schemas.android.com/apk/res-auto"      xmlns:tools="https://schemas.android.com/tools"      android:layout_width="match_parent"      android:layout_height="wrap_content"      android:layout_marginTop="10dp"      tools:context=".MainActivity"      >      <ImageView          android:id="@+id/lma_Picture"          android:layout_width="100dp"          android:layout_height="100dp"          android:scaleType="fitXY"          android:src="@mipmap/ic_launcher_round"          />      <LinearLayout          android:id="@+id/l_Layout"          android:layout_toRightOf="@id/lma_Picture"          android:layout_width="wrap_content"          android:layout_height="wrap_content"          android:orientation="vertical"          android:paddingTop="5dp"          >          <TextView              android:id="@+id/tv_Name"              android:layout_width="wrap_content"              android:layout_height="wrap_content"              android:layout_marginLeft="10dp"              android:text="哈利波特"              android:textSize="18sp"              />            <TextView              android:id="@+id/tv_Type"              android:layout_width="wrap_content"              android:layout_height="wrap_content"              android:layout_marginLeft="10dp"              android:text="科幻"              android:textSize="15sp"              android:layout_marginTop="2dp"              />          <TextView              android:id="@+id/tv_Sale"              android:layout_width="wrap_content"              android:layout_height="wrap_content"              android:layout_marginLeft="10dp"              android:text="已售500本"              android:textSize="15sp"              android:layout_marginTop="2dp"              />          <TextView              android:id="@+id/tv_Price"              android:layout_width="wrap_content"              android:layout_height="wrap_content"              android:layout_marginLeft="10dp"              android:layout_marginTop="2dp"              android:textSize="20sp"              android:text="￥58"              android:textColor="#FF5722"                />        </LinearLayout>      <Button          android:id="@+id/bt_Add"          android:layout_width="80dp"          android:layout_height="35dp"          android:layout_alignParentRight="true"          android:layout_centerVertical="true"          android:text="加入购物车"          android:background="#7793F8"          />  </RelativeLayout> 

activity_i.xm:效果图:
infoBean：
用来保存信息的bean
创建get和set方法

package com.example.application;    import java.util.ArrayList;  import java.util.List;    public class infoBean {      int Picture,Price;      String Name,Type,Sale;        public infoBean(int Picture,int Price,String Name,String Type,String Sale){          this.Name=Name;          this.Picture=Picture;          this.Price=Price;          this.Sale=Sale;          this.Type=Type;      }      public int getPicture() {          return Picture;      }        public void setPicture(int picture) {          Picture = picture;      }        public int getPrice() {          return Price;      }        public void setPrice(int price) {          Price = price;      }        public String getName() {          return Name;      }        public void setName(String name) {          Name = name;      }        public String getType() {          return Type;      }        public void setType(String type) {          Type = type;      }        public String getSale() {          return Sale;      }        public void setSale(String sale) {          Sale = sale;      }  } 

MyBaseAdapter:
最重要的是重写getView()的代码
通过viewHolder和setTag()缓存控件

package com.example.application;  import android.content.Context;  import android.view.LayoutInflater;  import android.view.View;  import android.view.ViewGroup;  import android.widget.BaseAdapter;  import android.widget.ImageView;  import android.widget.TextView;  import java.util.List;    public class MyBaseAdapter extends BaseAdapter {    private  List<infoBean> list;    private Context mContext;    public MyBaseAdapter(Context mcontext,List<infoBean> list){      this.mContext = mcontext;      this.list = list;  }      @Override      public int getCount() {          return list.size();      }        @Override      public Object getItem(int i) {          return list.get(i);      }        @Override      public long getItemId(int i) {          return i;      }        @Override      public View getView(int i, View view, ViewGroup viewGroup) {      ViewHolder viewHolder;      if(view == null){          viewHolder = new ViewHolder();          view = LayoutInflater.from(mContext).inflate(R.layout.activity_i,null);          //对viewHolder的属性进行赋值          viewHolder.ivPicture = view.findViewById(R.id.lma_Picture);          viewHolder.tvName = view.findViewById(R.id.tv_Name);          viewHolder.tvPrice = view.findViewById(R.id.tv_Price);          viewHolder.tvSale = view.findViewById(R.id.tv_Sale);          viewHolder.tvType = view.findViewById(R.id.tv_Type);          //使用setTag缓存起来方便多次重用          view.setTag(viewHolder);      }          else{ //如果缓存池中有对应的缓存，则直接通过getTag取出viewHolder          viewHolder = (ViewHolder) view.getTag();          }            infoBean bean = list.get(i);          viewHolder.ivPicture.setImageResource(bean.getPicture());          viewHolder.tvName.setText(bean.getName());          viewHolder.tvType.setText(bean.getType());          viewHolder.tvPrice.setText("￥"+String.valueOf(bean.getPrice()));          viewHolder.tvSale.setText(bean.getSale());          return view;      }        class ViewHolder{                //用于缓存控件        public ImageView ivPicture;        public TextView  tvName,tvType,tvSale,tvPrice;      }  } 

MainActivity:
获取数据源
创建自定义的适配器MyBaseAdapter

package com.example.application;  import androidx.appcompat.app.AppCompatActivity;  import android.os.Bundle;  import android.widget.ListView;  import java.util.ArrayList;  import java.util.List;  public class MainActivity extends AppCompatActivity {        @Override      protected void onCreate(Bundle savedInstanceState) {          super.onCreate(savedInstanceState);          setContentView(R.layout.activity_main);          List<infoBean> itemBeanList = new ArrayList<>();          for (int i = 0;i < 20; i ++){         //添加list的内容，可以通过其他方式获取，我这里为了方便              itemBeanList.add(new infoBean(R.mipmap.ic_launcher_round, i, "免费精选名字大全" + i,"类型"+i,"已售"+i));          }         ListView myListView = (ListView) findViewById(R.id.list_info);   //这里find的是activity_main.xml里的listview          //设置ListView的适配器          myListView.setAdapter(new MyBaseAdapter(this,itemBeanList));      }      } 

实现效果图

总结

Adapter适配器非常重要，非常实用、常用！