一、订制ListView的界面
1.先建立一个Fruit水果类
package com.example.listviewtest;
public class Fruit {
private String name;
private int imageId;
public Fruit(String name,int imageId) {
this.name=name;
this.imageId = imageId;
}
public String getName() {
return name;
}
public int getImageId() {
return imageId;
}
}
2.然后建立一个展示水果的LayOut文件
<?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" >
<ImageView
android:id="@+id/fruit_image"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView
android:id="@+id/fruit_name"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="10dip" />
</LinearLayout>
然后新建一个FruitAdapter适配器,来继承ArrayAdapter
package com.example.listviewtest;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.content.Context;
import java.util.List;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class FruitAdapter extends ArrayAdapter<Fruit> {
private int resourceId;
public FruitAdapter(Context context,int textViewResourceId,List<Fruit> objects) {
super(context,textViewResourceId,objects);
resourceId = textViewResourceId;
}
@Override
public View getView(int position,View convertView,ViewGroup parent) {
Fruit fruit = getItem(position);//获取当前项的Fruit实例
View view = LayoutInflater.from(getContext()).inflate(resourceId,null);
ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);
fruitImage.setImageResource(fruit.getImageId());
fruitName.setText(fruit.getName());
return view;
}
}
最后我们完善我们的主程序
package com.example.listviewtest;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import java.util.*;
//import java.lang.ArrayAdapter;
public class MainActivity extends Activity {
private List<Fruit> fruitList = new ArrayList<Fruit>();
// private String[] data = {"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFruits();//初始化水果数据
FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
// ArrayAdapter<String> adapter = new ArrayAdapter<String>(
// MainActivity.this,android.R.layout.simple_list_item_1,data);
ListView listView = (ListView) findViewById(R.id.list_view);
listView.setAdapter(adapter);
}
private void initFruits() {
Fruit apple = new Fruit("Apple",R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana",R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange =new Fruit("Orange",R.drawable.orange_pic);
fruitList.add(orange);
}
}
这样运行我们的代码,得到如下的结果
二、提升ListView的运行效率
1.我们通过下面的注释内容可以看出,这一段代码的重构,可以将画面的流畅程度提升,以及缓存一个ViewHolder对象就可以大幅度提升运行速度。
package com.example.listviewtest;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import android.content.Context;
import java.util.List;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
public class FruitAdapter extends ArrayAdapter<Fruit> {
private int resourceId;
public FruitAdapter(Context context,int textViewResourceId,List<Fruit> objects) {
super(context,textViewResourceId,objects);
resourceId = textViewResourceId;
}
@Override
public View getView(int position,View convertView,ViewGroup parent) {
Fruit fruit = getItem(position);//获取当前项的Fruit实例
// View view = LayoutInflater.from(getContext()).inflate(resourceId,null);
//上面我们注释掉一个View实例,我们下一行先初始化一个View实例
View view;
ViewHolder viewHolder;
if(convertView == null) {//如果这个View不存在的话,我们就直接建一个View
view = LayoutInflater.from(getContext()).inflate(resourceId,null);
viewHolder = new ViewHolder();
viewHolder.fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
viewHolder.fruitName = (TextView) view.findViewById(R.id.fruit_name);
view.setTag(viewHolder);//将ViewHolder存储在View中
}else {
view = convertView;//如果View已经存在了,那么我们就复用已经存在了的View,这样就可以避免再次重新生成View,节省了运行时间
viewHolder = (ViewHolder) view.getTag();//调用getTag方法,把ViewHolder重新取出。
}
//这里我们建立了一个内部类,用来存储已经生成了的fruitImage和fruieName的实例,就省的每次都需要通过findViewById的方法,来去内存中查找目标实例
viewHolder.fruitImage.setImageResource(fruit.getImageId());
viewHolder.fruitName.setText(fruit.getName());
// ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
// TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);
// fruitImage.setImageResource(fruit.getImageId());
// fruitName.setText(fruit.getName());
return view;
}
class ViewHolder{
ImageView fruitImage;
TextView fruitName;
}
}
三、ListView的点击事件
如果只列出了几条内容,我们不能通过点击List来来获取我们想要知道的信息,那将是毫无意义的。
接下来就在MainActivity中来注册我们的点击事件。
package com.example.listviewtest;
import java.util.List;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.Toast;
import java.util.*;
//import java.lang.ArrayAdapter;
public class MainActivity extends Activity {
private List<Fruit> fruitList = new ArrayList<Fruit>();
// private String[] data = {"Apple","Banana","Orange","Watermelon","Pear","Grape","Pineapple","Strawberry","Cherry"};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initFruits();//初始化水果数据
FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
// ArrayAdapter<String> adapter = new ArrayAdapter<String>(
// MainActivity.this,android.R.layout.simple_list_item_1,data);
ListView listView = (ListView) findViewById(R.id.list_view);
listView.setAdapter(adapter);
//接下来就来注册点击事件
listView.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent,View view,int position,long id) {
Fruit fruit = fruitList.get(position);
Toast.makeText(MainActivity.this, fruit.getName(), Toast.LENGTH_SHORT).show();
}
});
}
private void initFruits() {
Fruit apple = new Fruit("Apple",R.drawable.apple_pic);
fruitList.add(apple);
Fruit banana = new Fruit("Banana",R.drawable.banana_pic);
fruitList.add(banana);
Fruit orange =new Fruit("Orange",R.drawable.orange_pic);