简介：
ListView是手机上最常用的控件之一，几乎所有的程序都会用到，手机屏幕空间有限，当需要显示大量数据的时候，就需要借助ListView来实现，允许用户通过手指上下滑动的方式将屏幕外的数据滚动到屏幕内，同时原有的数据将滚动出去。
一、使用准备好的data数组来显示ListView
- 新建项目，修改activity_main.xml中的代码，增加ListView控件，简单设置属性
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.listviewtest.MainActivity" > <ListView
android:id="@+id/list_view"
android:layout_width="match_parent"
android:layout_height="match_parent"
/> </RelativeLayout> - 在主活动MainActivity.java中新建数据数组data，新建适配器，设置适配器显示
package com.example.listviewtest; import android.app.Activity;
import android.os.Bundle;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends Activity { //建立私有数组来存储要显示的数据
private String[] data = {"Apple","Banana","Orange","Watermelon","pear","Grape","Pineapple","Strawberry","Cherry","Mango"
,"Apple","Banana","Orange","Watermelon","pear","Grape","Pineapple","Strawberry","Cherry","Mango"}; @Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); //新建适配器来转换数据
ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_list_item_1,data); //实例化ListView
ListView listView = (ListView) findViewById(R.id.list_view); //给listView设置适配器，将ListView和数据联系起来
listView.setAdapter(adapter);
} }
二、定制ListView的界面，可以设置图片等、更加美观
- 新建实体类，来存放要显示的数据，这里使用的水果列表
package com.example.listviewtest; //存放水果信息的类
public class Fruit {
private String name ;//定义私有变量存储水果名称
private int imageId ;//定义私有变量存储水果图片ID //定义构造方法来初始化
public Fruit(String name , int imageId ) {
// TODO Auto-generated method stub
this.name = name;
this.imageId = imageId;
} //获取名称
public String getName() {
return name;
}
//获取图片ID
public int getImageId()
{
return imageId;
}
}Fruit
- 为ListView的子项指定一个自定义布局fruit_item.xml，ImageView显示水果图片，TextView显示水果名称
<?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="horizontal" > <ImageView
android:id="@+id/fruit_image"
android:layout_width="50sp"
android:layout_height="50sp"/> <TextView
android:id="@+id/fruit_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"居中显示 android:layout_marginLeft="10dip" 距离左侧10dip />
</LinearLayout> - 自定义适配器继承于ArrayAdapter，将泛型指定为Fruit类
package com.example.listviewtest; import java.util.List;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView; public class FruitAdapter extends ArrayAdapter<Fruit> {
//定义地址路径 resourceId
private int resourceId; //重写父类的构造方法，传入上下文，ListView子布局ID和数据传进来；
public FruitAdapter(Context context,int textViewResource,List<Fruit> object) {
// TODO Auto-generated constructor stub
super(context , textViewResource , object);
resourceId = textViewResource;
} //重写getView方法，返回View
@Override
public View getView(int position, View convertView, ViewGroup parent) { //获取当前页面的Fruit实例，根据屏幕上的菜单滚动得到
Fruit fruit = getItem(position); //使用Layoutinflater为这个子项加载我们传入的布局(resourceId)，
View view = LayoutInflater.from(getContext()).inflate(resourceId, null); //分别获取子布局中ImageView和TextView的实例
ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
TextView fruitName = (TextView) view.findViewById(R.id.fruit_name); //调用控件ImageView实例的setImageResource设置图片，TextView的setText方法设置文字；
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName()); //返回View
return view; }
}FruitAdapter类
- 重写MainActivity.java文件，
package com.example.listviewtest; import java.util.ArrayList;
import java.util.List;
import com.example.listviewtest.Fruit;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;
public class MainActivity extends Activity { //建立一个集合来存储实体类，实际上是水果的列表
private List<Fruit> fruitList = new ArrayList<Fruit>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); //实例化ListView控件为listView
ListView listView = (ListView) findViewById(R.id.list_view); //利用自定义方法初始化水果数据
initFruits(); //实例化适配器FruitAdapter，传入上下文、子布局、水果列表
FruitAdapter adapter = new FruitAdapter(MainActivity.this, R.layout.fruit_item, fruitList); //为listView设置适配器，联系ListView和数据
listView.setAdapter(adapter);
} //自定义方法初始化水果数据
private void initFruits() { //实例化水果对象；
Fruit apple = new Fruit("Apple",R.drawable.apple_pic); //将对象传入自定义列表中
fruitList.add(apple); //以下和上面是一个道理
Fruit banana = new Fruit("Banana", R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange = new Fruit("Orange",R.drawable.orange_pic);
fruitList.add(orange);
Fruit watermelon = new Fruit("Watermelon",R.drawable.watermelon_pic);
fruitList.add(watermelon);
Fruit pear = new Fruit("Pear",R.drawable.pear_pic);
fruitList.add(pear);
Fruit grape = new Fruit("Grape",R.drawable.grape_pic);
fruitList.add(grape);
Fruit pineapple = new Fruit("Pineapple", R.drawable.pineapple_pic);
fruitList.add(pineapple);
Fruit strawberry = new Fruit("Strawberry", R.drawable.strawberry_pic);
fruitList.add(strawberry);
Fruit cherry = new Fruit("Cherry", R.drawable.cherry_pic);
fruitList.add(cherry);
Fruit mango = new Fruit("Mango", R.drawable.mango_pic);
fruitList.add(mango);
} }MainActivity.java
- 显示效果（右键查看图像看大图）：
三、提升ListView的运行效率，基于上面二中的例子
主要解决的是： 1、在getView中每次都加载布局
2、getView中每次都要实例化控件的实例
- 优化一：通过判断FruitAdapter中的getView方法中的convertView是否为空进行优化；(红色为修改部分)
package com.example.listviewtest; import java.util.List;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView; public class FruitAdapter extends ArrayAdapter<Fruit> {
//定义地址路径 resourceId
private int resourceId; //重写父类的构造方法，传入上下文，ListView子布局ID和数据传进来；
public FruitAdapter(Context context,int textViewResource,List<Fruit> object) {
// TODO Auto-generated constructor stub
super(context , textViewResource , object);
resourceId = textViewResource;
} //重写getView方法，返回View
@Override
public View getView(int position, View convertView, ViewGroup parent) { //获取当前页面的Fruit实例，根据屏幕上的菜单滚动得到
Fruit fruit = getItem(position); //新建View对象
View view ;
32
33 //判断convertView对象是否为空，如果为空就重新加载；
34 if(convertView == null)
35 {
36 //使用Layoutinflater为这个子项加载我们传入的布局(resourceId)，
37 view = LayoutInflater.from(getContext()).inflate(resourceId, null);
38 }
39 else//如果不为空，则重新调用convertView；不必重新加载
40 {
41 view = convertView;
42 } //分别获取子布局中ImageView和TextView的实例
ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
TextView fruitName = (TextView) view.findViewById(R.id.fruit_name); //调用控件ImageView实例的setImageResource设置图片，TextView的setText方法设置文字；
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName()); //返回View
return view; }
} - 优化二：借助ViewHolder来对获取控件实例进行优化，修改Fruit中的代码，(对比上面的优化一，红色为修改部分)
package com.example.listviewtest; import java.util.List;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView; public class FruitAdapter extends ArrayAdapter<Fruit> {
//定义地址路径 resourceId
private int resourceId; //重写父类的构造方法，传入上下文，ListView子布局ID和数据传进来；
public FruitAdapter(Context context,int textViewResource,List<Fruit> object) {
// TODO Auto-generated constructor stub
super(context , textViewResource , object);
resourceId = textViewResource;
} //重写getView方法，返回View
@Override
public View getView(int position, View convertView, ViewGroup parent) { //获取当前页面的Fruit实例，根据屏幕上的菜单滚动得到
Fruit fruit = getItem(position); //新建View对象
View view ; //声明
34 ViewHolder viewHolder; //判断convertView对象是否为空，如果为空就重新加载；
if(convertView == null)
{
//使用Layoutinflater为这个子项加载我们传入的布局(resourceId)，
view = LayoutInflater.from(getContext()).inflate(resourceId, null);
//实例化一个ViewHolder
viewHolder = new ViewHolder();
43 //将控件的实例都存在ViewHolder中
44 viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
45 viewHolder.fruitname = (TextView) view.findViewById(R.id.fruit_name);
46 //吧ViewHolder存储在View中；
47 view.setTag(viewHolder);
}
else//如果不为空，则重新调用convertView；不必重新加载
{
view = convertView;
//重新获取ViewHolder
viewHolder = (ViewHolder) view.getTag();
} //分别获取子布局中ImageView和TextView的实例
// ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
// TextView fruitName = (TextView) view.findViewById(R.id.fruit_name); //调用控件ImageView实例的setImageResource设置图片，TextView的setText方法设置文字；
// fruitImage.setImageResource(fruit.getImageId());
// fruitName.setText(fruit.getName()); //在ViewHolder中完成设置
65 viewHolder.fruitImage.setImageResource(fruit.getImageId());
66 viewHolder.fruitname.setText(fruit.getName()); //返回View
return view; }
}
class ViewHolder {
ImageView fruitImage;
TextView fruitname;
}
总结：通过上面两部的优化，已经很大程度上提高了ListView的运行效率了；
最终效果图：
追加：为ListView设置点击事件；
在MainActivity中加入ListView的监听事件
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
//获取当前点击的Fruit对象
Fruit fruit = fruitList.get(position);
//利用Toast提示点击事件
Toast.makeText(MainActivity.this, "You Clicked The"+fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
效果图：