//创建一个URL对象

 URL url = new URL(urlString);

 //创建一个HttpURLConnection

 HttpURLConnetion urlConn = (HttpURLConnection)url.openConnecton();

 //读取数据

 BufferReader buffer = new BufferReader(new InputStreamReader(urlConn.getInputStream()));

 StringBuffer sb = null;

 String line = null;

 while((line = buffer.readline()) != null){

     sb.append(line);

 }

//创建一个URL对象

URL url = new URL(urlString);

//创建一个HttpURLConnection

HttpURLConnection urlConn ＝(HttpURLConnection)url.openConnection();

//获取一个InputStream

InputStream inputStream = urlConn.getInputStream();

//获取SD卡的路径

String SDPath = Environment.getExternalStorageDirectory() + "/";

//创建要使用的文件夹

File dir = new File(SDPath + dirName);

dir.mkdirs();

//创建输出文件

File file = new File(SDPath + dirName + fileName);

file.createNewFile();

//创建一个文件输出流

OutputStream output = new FileOutputStream(file);

//建立缓冲

byte[] buffer = new byte[1*1024];

//Stream读取索引

int downloadNum = 0;

//将输入流写到文件当中

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

   output.write(buffer, 0, downloadNum);

}

output.flush();