Android课程---优化ListView列表视图

<?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/sa_1">

</ListView>

<?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="wrap_content">
    <ImageView
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:src="@drawable/yuantu"
        android:id="@+id/lv2"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="20dp">
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="美食图片"
            android:id="@+id/tv1"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="很好吃啊"
            android:id="@+id/tv2"/>

    </LinearLayout>

</LinearLayout>

package com.hanqi.test5;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.ListView;
import android.widget.SimpleAdapter;

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

public class UIActivity4 extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ui4);

        ListView sa_1 =(ListView)findViewById(R.id.sa_1);

        //准备数据源
        List<Map<String,Object>> lm =new ArrayList<Map<String,Object>>();
        Map<String,Object> map = new Hashtable<String, Object>();

        map.put("image",R.drawable.yuantu);
        map.put("name","美食图片01");
        map.put("content","很好吃啊01");
        lm.add(map);

        map = new Hashtable<String, Object>();
        map.put("image",R.drawable.yuantu);
        map.put("name","美食图片02");
        map.put("content","很好吃啊02");
        lm.add(map);

        map = new Hashtable<String, Object>();
        map.put("image",R.drawable.yuantu);
        map.put("name","美食图片03");
        map.put("content","很好吃啊03");
        lm.add(map);

        map = new Hashtable<String, Object>();
        map.put("image",R.drawable.yuantu);
        map.put("name","美食图片04");
        map.put("content","很好吃啊04");
        lm.add(map);

        //1.数组源里key数组
        String[] str ={"image","name","content"};

        //2.layout文件里面子视图的id
        int[] viewid = {R.id.lv2,R.id.tv1,R.id.tv2,};

        SimpleAdapter sa = new SimpleAdapter(this,lm,R.layout.layout_simple,str,viewid);

        sa_1.setAdapter(sa);
    }
}