Android DownloadManager 的使用

public static long downloadMusic(String url, String artist, String song){        Uri uri = Uri.parse(url);        DownloadManager.Request request = new DownloadManager.Request(uri);        String mp3FileName = FileUtils.getMp3FileName(artist, song);        //设置下载文件存放路径        request.setDestinationInExternalPublicDir(FileUtils.getRelativeMusicDir(), mp3FileName);        //设置MimeType用于响应点击下载完后响应的事件        request.setMimeType(MimeTypeMap.getFileExtensionFromUrl(url));        //表示允许MediaScanner扫描到这个文件，默认不允许        request.allowScanningByMediaScanner();        //设置允许下载的数据类型        request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_MOBILE | DownloadManager.Request.NETWORK_WIFI);        //移动网络情况下是否允许漫游,不允许        request.setAllowedOverRoaming(false);        DownloadManager downloadManager = (DownloadManager) AppCache.getContext().getSystemService(Context.DOWNLOAD_SERVICE);        return downloadManager.enqueue(request);    }