Adapter

ArrayAdapter
数组适配器，仅能显示一行文本数据

<?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">
    <ListView
        android:id="@+id/lv_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </ListView>
</LinearLayout>

import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class MainActivity extends Activity {
    // 定义要显示的数据
    private String[] datas = {"张三", "李四", "王五", "麻子", "小强"};
    private ArrayAdapter<String> adapter;
    private ListView listView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.lv_list);
        // 初始化适配器
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_expandable_list_item_1, datas);
        listView.setAdapter(adapter);
    }
}

可以在value创建数组资源xml文件arrays.xml，在listview中使用entries

<resources>
    <string-array name = "list">
        <item>张三</item>
        <item>李四</item>
        <item>王五</item>
        <item>麻子</item>
        <item>小强</item>
      </string-array>
</resources>

<ListView
    android:id="@+id/lv_list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:entries="@array/list">
</ListView>

datas = getResources().getStringArray(R.array.list);

listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
    @Override
    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
        String result = parent.getItemAtPosition(position).toString();
        Toast.makeText(MainActivity.this, result, Toast.LENGTH_SHORT).show();
    }
});

ArrayAdapter参数说明

• 第一个参数，context上下文对象
• 第二个参数，item样式，可以使用系统提供，可以自定义TextView
• 第三个参数，数据源

系统提供item样式

• simple_list_item1，单行文本框（text）
• simple_list_item2，两行文本框（title与text）
• simple_list_item_checked，复选框（已选中）
• simple_list_item_multiple_choice，复选框
• simple_list_item_single_choice，单选框

SimpleAdapter
简单适配器

<?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">
    <ListView
        android:id="@+id/lv_list"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
    </ListView>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:orientation="horizontal">
    <ImageView
        android:id="@+id/iv_image"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:src="@mipmap/ic_launcher"
        android:layout_margin="5dp"/>
   <LinearLayout
       android:id="@+id/ll_info"
       android:layout_width="match_parent"
       android:layout_height="100dp"
       android:orientation="vertical"
       android:layout_marginTop="5dp"
       android:layout_marginLeft="10dp">
       <TextView
           android:id="@+id/tv_theme"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:textSize="30sp"
           android:layout_marginTop="10dp"/>
       <TextView
           android:id="@+id/tv_content"
           android:layout_width="wrap_content"
           android:layout_height="wrap_content"
           android:textSize="24dp"
           android:layout_marginTop="10dp"/>
   </LinearLayout>
</LinearLayout>

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;
import android.widget.SimpleAdapter;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class MainActivity extends Activity {
    private List<Map<String,Object>> lists;
    private SimpleAdapter adapter;
    private ListView listView;
    // 定义数据
    private String[] theme = {"张三", "李四", "王五"};
    private String[] content = {"我是张三，你好", "我是李四，你好", "我是王五，你好"};
    private int[] imageViews = {R.mipmap.ic_launcher, R.mipmap.ic_account, R.mipmap.ic_password};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.lv_list);
        // 准备数据源
        lists = new ArrayList<>();
        for(int i = 0; i < theme.length; i++) {
            Map<String,Object> map = new HashMap<>();
            map.put("image", imageViews[i]);
            map.put("theme", theme[i]);
            map.put("content", content[i]);
            lists.add(map);
        }
        adapter = new SimpleAdapter(MainActivity.this, lists, R.layout.list_item, new String[]{"image", "theme", "content"}, new int[]{R.id.iv_image, R.id.tv_theme, R.id.tv_content});
        listView.setAdapter(adapter);
    }
}

SimpleAdapter参数说明

• 第一个参数，上下文对象
• 第二个参数，数据源（集合，元素类型Map）
• 第三个参数，item布局文件
• 第四个参数，String数组，数组元素与数据源Map的key一一对应
• 第五个参数，int数组，item布局文件的控件id

BaseAdapter

import android.content.Context;
import android.text.Layout;
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.ArrayList;
import java.util.List;

public class InfoAdapter extends BaseAdapter {
    private List<Message> datas;
    private Context mContext;

    public MyAdapter(List<Message> datas, Context mContext) {
        Datas = datas;
        this.mContext = mContext;
    }

    /**
     * 返回item个数
     * @return
     */
    @Override
    public int getCount() {
        return datas.size();
    }

    /**
     * 返回单个item对象
     * @param i
     * @return
     */
    @Override
    public Object getItem(int i) {
        return datas.get(i);
    }

    /**
     * 返回单个item的id
     * @param i
     * @return
     */
    @Override
    public long getItemId(int i) {
        return i;
    }

    /**
     * 暂不进行优化处理
     * @param i
     * @param view
     * @param viewGroup
     * @return
     */
    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        view = LayoutInflater.from(mContext).inflate(R.layout.list_item, viewGroup, false);
        ImageView iv_image = (ImageView) view.findViewById(R.id.iv_image);
        TextView tv_theme = (TextView) view.findViewById(R.id.tv_theme);
        TextView tv_content = (TextView) view.findViewById(R.id.tv_content);
        iv_image.setImageResource(Datas.get(i).getImageId());
        tv_theme.setText(Datas.get(i).getTheme());
        tv_content.setText(Datas.get(i).getContent());
        return view;
    }
}

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

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

public class MainActivity extends Activity {
    private List<Message> lists;
    private InfoAdapter adapter;
    private ListView listView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        listView = (ListView) findViewById(R.id.ll_list);
        lists = new ArrayList<>();
        lists.add(new Message(R.mipmap.ic_launcher, "张三", "你好，我是张三"));
        lists.add(new Message(R.mipmap.ic_account, "李四", "你好，我是李四"));
        lists.add(new Message(R.mipmap.ic_password, "王五", "你好，我是王五"));
        adapter = new InfoAdapter(lists, MainActivity.this);
        listView.setAdapter(adapter);
    }
}

利用Listview缓存机制但findviewbyid反复使用

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // 若view未被实例化，缓存池无对应缓存
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.item, null);
    }
    /**
     * 获取item布局文件对应控件
     */
    ImageView imageView = (ImageView) convertView.findViewById(R.id.iv_image);
    TextView titleTextView = (TextView) convertView.findViewById(R.id.tv_theme);
    TextView contentTextView = (TextView) convertView.findViewById(R.id.tv_content);
    // 获取相应索引ItemBean对象
    ItemBean bean = mList.get(position);
    /**
     * 设置控件的对应属性值
     */
    imageView.setImageResource(bean.itemImageResId);
    titleTextView.setText(bean.itemTheme);
    contentTextView.setText(bean.itemContent);
    return convertView;
}

1. 创建bean对象，用于封装数据
2. 在构造方法中初始化数据List
3. 创建ViewHolder类，创建布局映射关系
4. 判断convertView，为空则创建并设置tag，不为空则通过tag取出ViewHolder
5. 给ViewHolder控件设置数据

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    ViewHolder viewHolder;
    // 若view未被实例化过，缓存池无对应缓存
    if (convertView == null) {
        viewHolder = new ViewHolder();
        // 仅需将XML转化为View，不涉及布局，第二个参数设置为null
        convertView = mInflater.inflate(R.layout.item, null);
        // 对viewHolder属性进行赋值
        viewHolder.imageView = (ImageView) convertView.findViewById(R.id.iv_image);
        viewHolder.theme = (TextView) convertView.findViewById(R.id.tv_theme);
        viewHolder.content = (TextView) convertView.findViewById(R.id.tv_content);
        // 通过setTag将convertView与viewHolder关联
        convertView.setTag(viewHolder);
    } else {
        // 若缓存池有对应view缓存，则通过getTag取出viewHolder
        viewHolder = (ViewHolder) convertView.getTag();
    }
    // 取出bean对象
    ItemBean bean = mList.get(position);
    // 设置控件的数据
    viewHolder.imageView.setImageResource(bean.itemImageResId);
    viewHolder.title.setText(bean.itemTheme);
    viewHolder.content.setText(bean.itemContent);

    return convertView;
}
// ViewHolder用于缓存控件，属性对应item布局文件控件
class ViewHolder{
    public ImageView imageView;
    public TextView theme;
    public TextView content;
}