在安卓系统中DownloadManager没有显示进度条吗？

// 创建一个自定义的通知布局文件，例如 notification_download.xml

// 在应用的代码中发起下载请求
DownloadManager downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
DownloadManager.Request request = new DownloadManager.Request(Uri.parse("下载链接"));
long downloadId = downloadManager.enqueue(request);

// 注册一个BroadcastReceiver来接收DownloadManager的下载状态变化广播
BroadcastReceiver downloadReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        if (DownloadManager.ACTION_DOWNLOAD_COMPLETE.equals(action)) {
            // 下载完成
            long completedDownloadId = intent.getLongExtra(DownloadManager.EXTRA_DOWNLOAD_ID, -1);
            if (completedDownloadId == downloadId) {
                // 更新通知栏中的相关信息，例如显示下载完成的提示
            }
        } else if (DownloadManager.ACTION_NOTIFICATION_CLICKED.equals(action)) {
            // 用户点击了通知栏，可以打开下载文件或者跳转到应用界面
        } else if (DownloadManager.ACTION_DOWNLOAD_STATUS_CHANGED.equals(action)) {
            // 下载状态变化
            DownloadManager.Query query = new DownloadManager.Query();
            query.setFilterById(downloadId);
            Cursor cursor = downloadManager.query(query);
            if (cursor.moveToFirst()) {
                int status = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
                if (status == DownloadManager.STATUS_RUNNING) {
                    // 下载中，获取下载进度并更新通知栏中的进度条
                    int totalSize = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_TOTAL_SIZE_BYTES));
                    int downloadedSize = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_BYTES_DOWNLOADED_SO_FAR));
                    int progress = (int) (downloadedSize * 100.0 / totalSize);
                    // 更新通知栏中的进度条
                }
            }
            cursor.close();
        }
    }
};

// 注册广播接收器
registerReceiver(downloadReceiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_COMPLETE));
registerReceiver(downloadReceiver, new IntentFilter(DownloadManager.ACTION_NOTIFICATION_CLICKED));
registerReceiver(downloadReceiver, new IntentFilter(DownloadManager.ACTION_DOWNLOAD_STATUS_CHANGED));