new Thread(new Runnable() {

			@Override

			public void run() {

				// TODO Auto-generated method stub

				try {

					updateFile = Environment.getExternalStorageDirectory()

							+ "/3530.jpg";

					//downloadUpdateFile("http://image.anzimall.com/3530/3530_K21D_app_V2.3_2015050528.bin",  updateFile);

					downloadUpdateFile("http://img1.cache.netease.com/catchpic/F/FC/FCC085159B92C5EE4FDDB9618166051E.jpg",  updateFile);

				} catch (Exception e) {

					// TODO Auto-generated catch block

					e.printStackTrace();  //android.os.NetworkOnMainThreadException

					System.out.println(e.toString()+"");

				}

			}

		}).start();

public static long downloadUpdateFile(String down_url, String file)

			throws Exception {

		int downloadCount = 0;// 已经下载好的大小

		InputStream inputStream;

		OutputStream outputStream;

		URL url = new URL(down_url);

		HttpURLConnection httpurlconnection = (HttpURLConnection) url

				.openConnection();

		httpurlconnection.setConnectTimeout(5000);

		httpurlconnection.setReadTimeout(5000);

		// 获取下载文件的size

		//totalSize = httpURLConnection.getContentLength();

		if (httpurlconnection.getResponseCode() == 404) {

			throw new Exception("fail!");

			// 这个地方应该加一个下载失败的处理，但是，因为我们在外面加了一个try---catch，已经处理了Exception,

			// 所以不用处理

		}

		inputStream = httpurlconnection.getInputStream();

                File file_ok = new File(file);

		outputStream = new FileOutputStream(file_ok);// 文件存在则覆盖掉

		byte buffer[] = new byte[1024];

		int readsize = 0;

		while ((readsize = inputStream.read(buffer)) != -1) {

			outputStream.write(buffer, 0, readsize);

			downloadCount += readsize;// 时时获取下载到的大小

		}

		if (httpurlconnection != null) {

			httpurlconnection.disconnect();

		}

		inputStream.close();

		outputStream.close();

		return downloadCount;

	}