下载管理器有时显示不成功

Question

正如标题所述，我有一个下载管理器，它可以工作，但仅有时。这很奇怪，我找不到模式。我有一个按钮，当单击该按钮时，它会将请求发送到服务器，该服务器返回要下载的文件，然后有时会下载，有时则不会。我看不到任何模式，电话或服务器也没有收到任何错误。

这对我的应用程序不利，因为我需要知道它已成功下载，所以我要么需要找出有时为何它不起作用的原因，要么需要找到一种在下载失败时运行功能的方法。这是我用来下载文件的代码：

        GlobalVariables globalVariables = new GlobalVariables();
        String url = globalVariables.getIPAddress() + "downloadsong/" + Integer.toString(songId) + "/";
        SharedPreferences sharedPreferences = getSharedPreferences("StoredValues", MODE_PRIVATE);
        String token = sharedPreferences.getString("token", "null");

        DownloadManager downloadManager = (DownloadManager)getSystemService(DOWNLOAD_SERVICE);
        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
        request.setTitle("Downloading");
        request.setDescription("Downloading new titles");
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
        request.setDestinationInExternalPublicDir(Environment.DIRECTORY_MUSIC, "" + songId + ".mp3");
        request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI);
        request.addRequestHeader("Authorization", "Token " + token);
        request.allowScanningByMediaScanner();
        request.setAllowedOverMetered(true);
        request.setAllowedOverRoaming(true);

        long downloadReference = downloadManager.enqueue(request);
        if (downloadReference != 0) {
            Toast.makeText(getApplicationContext(), "download started", Toast.LENGTH_SHORT).show();
        }else {
            Toast.makeText(getApplicationContext(), "no download started", Toast.LENGTH_SHORT).show();
        }

感谢您的帮助或见识。谢谢！

Answer 1

您必须注册一个广播接收者

public static int validDownload(Context context, long downloadId) {
    //Verify if download is a success
    DownloadManager dm = (DownloadManager) context.getSystemService(Context.DOWNLOAD_SERVICE);
    Cursor c = dm.query(new DownloadManager.Query().setFilterById(downloadId));

    try {
        if (c.moveToFirst()) {
            int status = c.getInt(c.getColumnIndex(DownloadManager.COLUMN_STATUS));

            if (status == DownloadManager.STATUS_SUCCESSFUL) {
                return 0; //Download is valid, celebrate
            } else {
                return c.getInt(c.getColumnIndex(DownloadManager.COLUMN_REASON));
            }
        }
    } finally {
        c.close();
    }

    return -1; 
}


private BroadcastReceiver onDownloadComplete = new BroadcastReceiver() {
   @Override
   public void onReceive(Context context, Intent intent) {

       //Fetching the download id received with the broadcast
       long id = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);

       //Checking if the received broadcast is for our enqueued download by matching download id
       if (downloadID == id) {
           validDownload(this, id);
       }

   }

};

并在您的活动的onCreate方法中注册ACTION_DOWNLOAD_COMPLETE。

  @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    registerReceiver(onDownloadComplete, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
}