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, "名字" + 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！