Android多線程下載遠程圖片

http://blog.csdn.net/longlong3050/article/details/6709528

修改後的代碼

import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.net.HttpURLConnection;
import java.net.URL;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.AsyncTask;
import android.util.Log;
import android.widget.ImageView;
/**
 * @類名：ImageDownloader
 * @功能描述：優化的ImageDownloader, 不帶緩存，在線下載，用戶頭像請使用。
 * @作者： William Xu
 * @創建日期：2013-6-7
 * @修改人：
 * @修改日期：
 * @修改備註：
 * @版本號：1.0
 */
public class ImageDownloader {
    public void download(String url, ImageView p_w_picpathView) {
        BitmapDownloaderTask task = new BitmapDownloaderTask(p_w_picpathView);
        task.execute(url);
    }
    class BitmapDownloaderTask extends AsyncTask<String, Void, Bitmap> {
          
        private final WeakReference<ImageView> p_w_picpathViewReference; // 使用WeakReference解決內存問題
        public BitmapDownloaderTask(ImageView p_w_picpathView) {
            p_w_picpathViewReference = new WeakReference<ImageView>(p_w_picpathView);
        }
        @Override
        protected Bitmap doInString...  params) { // 實際的下載線程，內部其實是concurrent線程，所以不會阻塞
            Bitmap bitmap = null;
            try {
                URL p_w_picpathUrl = new URL(params[0]);
                HttpURLConnection conn = (HttpURLConnection) p_w_picpathUrl
                        .openConnection();
                conn.setConnectTimeout(30000);
                conn.setReadTimeout(30000);
                conn.setInstanceFollowRedirects(true);
                InputStream is = conn.getInputStream();
                bitmap = BitmapFactory.decodeStream(is);
            } catch (Exception ex) {
                Log.e("",
                        "getBitmap catch Exception...\nmessage = "
                                + ex.getMessage());
            }
            return bitmap;
        }
        @Override
        protected void onPostExecute(Bitmap bitmap) { // 下載完後執行的
            if (isCancelled()) {
                bitmap = null;
            }
            if (p_w_picpathViewReference != null) {
                  
                ImageView p_w_picpathView = p_w_picpathViewReference.get();
                  
                if (p_w_picpathView != null && bitmap != null) {
                      
                    p_w_picpathView.setImageBitmap(bitmap); // 下載完設置p_w_picpathview爲剛纔下載的bitmap對象
                }
            }
        }
    }
}