URL url = newURL(http://somewhere.com/some/webhosted/file);
HttpURLConnectionurlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
urlConnection.connect();
File SDCardRoot = Environment.getExternalStorageDirectory();
File file = new File(SDCardRoot,"somefile.ext");
FileOutputStream fileOutput = new FileOutputStream(file);
InputStream inputStream = urlConnection.getInputStream();
int totalSize = urlConnection.getContentLength();
pd.setMax(totalSize);//ProgressDialog  pd
int downloadedSize = 0;
byte[] buffer = new byte[1024];
int bufferLength = 0;
while ( (bufferLength = inputStream.read(buffer)) > 0 ) {
    fileOutput.write(buffer, 0, bufferLength);
    downloadedSize += bufferLength; ;
    pd.setProgress(downloadedSize);//ProgressDialog  pd
}

Android下载文件的进度条提示（网络通信部分示例）