Android根据URL下载文件保存到SD卡

 //下载具体操作
    private void download() {
        try {
            URL url = new URL(downloadUrl);
            //打开连接
            URLConnection conn = url.openConnection();
            //打开输入流
            InputStream is = conn.getInputStream();
            //获得长度
            int contentLength = conn.getContentLength();
            Log.e(TAG, "contentLength = " + contentLength);
            //创建文件夹 MyDownLoad，在存储卡下
            String dirName = Environment.getExternalStorageDirectory() + "/MyDownLoad/";
            File file = new File(dirName);
            //不存在创建
            if (!file.exists()) {
                file.mkdir();
            }
            //下载后的文件名
            String fileName = dirName + "xiaomibianqian.apk";
            File file1 = new File(fileName);
            if (file1.exists()) {
                file1.delete();
            }
            //创建字节流
            byte[] bs = new byte[1024];
            int len;
            OutputStream os = new FileOutputStream(fileName);
            //写数据
            while ((len = is.read(bs)) != -1) {
                os.write(bs, 0, len);
            }
            //完成后关闭流
            Log.e(TAG, "download-finish");
            os.close();
            is.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
    String dirName = Environment.getExternalStorageDirectory() + "/MyDownLoad/";
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>