Android 用线程来实现远程下载

Java代码：

static Bitmap downloadBitmapByCwj(String url) { 
final AndroidHttpClient client = AndroidHttpClient.newInstance("Android123"); 
final HttpGet getRequest = new HttpGet(url); 

try { 
HttpResponse response = client.execute(getRequest); 
final int statusCode = response.getStatusLine().getStatusCode(); 
if (statusCode != HttpStatus.SC_OK) { 
Log.e("cwjDebug", "Error " + statusCode + " while retrieving bitmap from " + url); 
return null; 
} 

final HttpEntity entity = response.getEntity(); 
if (entity != null) { 
InputStream inputStream = null; 
try { 
inputStream = entity.getContent(); 
final Bitmap bitmap = BitmapFactory.decodeStream(inputStream); 
return bitmap; 
} finally { 
if (inputStream != null) { 
inputStream.close(); 
} 
entity.consumeContent(); 
} 
} 
} catch (Exception e) { 
getRequest.abort(); 
Log.e("android123Debug", "Error while retrieving bitmap from " + url, e.toString()); 
} finally { 
if (client != null) { 
client.close(); 
} 
} 
return null; 
}

static class FlushedInputStream extends FilterInputStream { 
public FlushedInputStream(InputStream inputStream) { 
super(inputStream); 
} 

@Override 
public long skip(long n) throws IOException { 
long totalBytesSkipped = 0L; 


while (totalBytesSkipped < n) { 
long bytesSkipped = in.skip(n - totalBytesSkipped); 


if (bytesSkipped == 0L) { 
int byte = read(); 
if (byte < 0) { 
break; // we reached EOF 
} else { 
bytesSkipped = 1; // 我们读到一个字节
} 
} 
totalBytesSkipped += bytesSkipped; 
} 
return totalBytesSkipped; 


} 


}

Java代码：

public class ImageDownloader { 

public void download(String url, ImageView imageView) { 
BitmapDownloaderTask task = new BitmapDownloaderTask(imageView); 
task.execute(url); 
} 
} 

}

Java代码：

class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> { 
private String url; 
private final WeakReference<ImageView> imageViewReference; //使用WeakReference解决内存问题

public BitmapDownloaderTask(ImageView imageView) { 
imageViewReference = new WeakReference<ImageView>(imageView); 
} 

@Override 
protected Bitmap doInBackground(String... params) { //实际的下载线程，内部其实是concurrent线程，所以不会阻塞

return downloadBitmap(params[0]); 
} 

@Override 
protected void onPostExecute(Bitmap bitmap) { //下载完后执行的
if (isCancelled()) { 
bitmap = null; 
} 

if (imageViewReference != null) { 
ImageView imageView = imageViewReference.get(); 
if (imageView != null) { 
imageView.setImageBitmap(bitmap); //下载完设置imageview为刚才下载的bitmap对象
} 
} 
} 
}