[android] 练习使用ListView（二）详解手机开发

package com.android.test; 
import java.io.InputStream; 
import java.net.HttpURLConnection; 
import java.net.URL; 
import com.nostra13.universalimageloader.core.ImageLoader; 
import com.nostra13.universalimageloader.core.ImageLoaderConfiguration; 
import com.nostra13.universalimageloader.core.assist.FailReason; 
import com.nostra13.universalimageloader.core.listener.ImageLoadingListener; 
import android.app.Activity; 
import android.graphics.Bitmap; 
import android.graphics.BitmapFactory; 
import android.graphics.drawable.BitmapDrawable; 
import android.os.AsyncTask; 
import android.os.Bundle; 
import android.support.v4.util.LruCache; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.ImageView; 
import android.widget.ListAdapter; 
import android.widget.ListView; 
import android.widget.TextView; 
public class MainActivity extends Activity { 
private ListView lv_images; 
@Override 
protected void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_main); 
lv_images = (ListView) findViewById(R.id.lv_images); 
ImageLoaderConfiguration configuration=ImageLoaderConfiguration.createDefault(this); 
ImageLoader.getInstance().init(configuration); 
ListAdapter adapter = new ImageAdapter(); 
lv_images.setAdapter(adapter); 
} 
/** 
* 适配器 
* @author taoshihan 
* 
*/ 
class ImageAdapter extends BaseAdapter { 
private LruCache<String, BitmapDrawable> mImageCache; 
public ImageAdapter() { 
int maxSize=(int) (Runtime.getRuntime().maxMemory()/8); 
mImageCache=new LruCache<String, BitmapDrawable>(maxSize){ 
protected int sizeOf(String key, BitmapDrawable drawable) { 
return drawable.getBitmap().getByteCount();  
}; 
}; 
} 
@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
String url=(String) getItem(position); 
View view; 
if(convertView!=null){ 
view=convertView; 
}else{ 
view=View.inflate(getApplicationContext(), R.layout.image_item, null); 
} 
ImageView imageView=(ImageView) view.findViewById(R.id.tv_image); 
BitmapDrawable bitmapDrawable=getBitmapFromMemoryCache(url); 
if(bitmapDrawable!=null){ 
//读取缓存图片 
                imageView.setImageDrawable(bitmapDrawable); 
}else{ 
//读取网络图片 
ImageWorkerTask task=new ImageWorkerTask(imageView); 
task.execute(url); 
} 
return view; 
} 
/** 
* 从缓存中读取图片 
* @param key 
* @return  
*/ 
public BitmapDrawable getBitmapFromMemoryCache(String key) { 
if(mImageCache.get(key)!=null){ 
return mImageCache.get(key); 
} 
return null; 
} 
public void addBitmapToMemoryCache(String key,BitmapDrawable drawable){ 
if(getBitmapFromMemoryCache(key)==null){ 
mImageCache.put(key, drawable); 
} 
} 
@Override 
public int getCount() { 
// TODO Auto-generated method stub 
return Images.IMAGE_URLS.length; 
} 
@Override 
public Object getItem(int position) { 
return Images.IMAGE_URLS[position]; 
} 
@Override 
public long getItemId(int position) { 
// TODO Auto-generated method stub 
return position; 
} 
/** 
* 异步任务 
* @author taoshihan 
* 
*/ 
class ImageWorkerTask extends AsyncTask<String, Void, BitmapDrawable>{ 
private ImageView imageView; 
public ImageWorkerTask(ImageView imageView) { 
this.imageView=imageView; 
} 
@Override 
protected BitmapDrawable doInBackground(String... params) { 
String imageUrl=params[0]; 
Bitmap bitmap=downLoadBitmap(imageUrl); 
BitmapDrawable drawable=new BitmapDrawable(getApplicationContext().getResources(),bitmap); 
addBitmapToMemoryCache(imageUrl, drawable); 
return drawable; 
} 
//下载图片 
private Bitmap downLoadBitmap(String imageUrl) { 
Bitmap bitmap=null; 
try { 
URL url=new URL(imageUrl); 
HttpURLConnection conn=(HttpURLConnection) url.openConnection(); 
conn.setConnectTimeout(10000); 
InputStream is=conn.getInputStream(); 
bitmap=BitmapFactory.decodeStream(is); 
} catch (Exception e) { 
} 
return bitmap; 
} 
//下载完成的 
            @Override 
protected void onPostExecute(BitmapDrawable result) { 
if(imageView!=null&&result!=null){ 
imageView.setImageDrawable(result); 
} 
} 
} 
} 
static class Images{ 
public final static String[] IMAGE_URLS = new String[]{ 
"http://img.my.csdn.net/uploads/201508/05/1438760758_3497.jpg",     
"http://img.my.csdn.net/uploads/201508/05/1438760758_6667.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760757_3588.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760756_3304.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760755_6715.jpeg",   
"http://img.my.csdn.net/uploads/201508/05/1438760726_5120.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760726_8364.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760725_4031.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760724_9463.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760724_2371.jpg",   
"http://img.my.csdn.net/uploads/201508/05/1438760707_4653.jpg" 
}; 
} 
}