问当我的闹钟触发onReceive()时不显示通知

EN

@Override
public void onReceive(Context context, Intent intent) {
    PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE);
    PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "YOUR TAG");
    //Acquire the lock
    wl.acquire(10000);

    startNotification(context);

    wl.release();

}


public void setAlarm(Context context){
    AlarmManager am=(AlarmManager)context.getSystemService(Context.ALARM_SERVICE);
    Intent intent = new Intent(context, AlarmManagerBroadcastReceiver.class);
    intent.putExtra(Activity, "MainActivity.class");
    PendingIntent pi = PendingIntent.getBroadcast(context, 0, intent, 0);
    assert am != null;
    am.set(AlarmManager.RTC_WAKEUP, 60000, pi);
}


private void startNotification(Context context){
    // Sets an ID for the notification
    int mNotificationId = 001;
    NotificationManager notificationManager;
    NotificationCompat.Builder mBuilder;

            // Build Notification , setOngoing keeps the notification always in status bar
    mBuilder =
            new NotificationCompat.Builder(context)
                    .setSmallIcon(R.drawable.ic_launcher_foreground)
                    .setContentTitle("RandomTitle")
                    .setContentText("RandomText")
                    .setOngoing(true);

    // Create pending intent, mention the Activity which needs to be
    //triggered when user clicks on notification(StopScript.class in this case)

    Intent notificationIntent = new Intent(context, MainActivity.class);
    notificationIntent.putExtra("extra","Extra Notificacion");
    notificationIntent.addFlags(Intent.FLAG_ACTIVITY_BROUGHT_TO_FRONT |
            Intent.FLAG_ACTIVITY_SINGLE_TOP);
    PendingIntent contentIntent = PendingIntent.getActivity(context, 0, notificationIntent , PendingIntent.FLAG_UPDATE_CURRENT);
   // context.startActivity(notificationIntent);

    mBuilder.setContentIntent(contentIntent);


    // Gets an instance of the NotificationManager service
     notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);

    //Android Oreo
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        NotificationChannel channel = new NotificationChannel("notify_001",
                "Channel human readable title",
                NotificationManager.IMPORTANCE_DEFAULT);
        notificationManager.createNotificationChannel(channel);
    }

    // Builds the notification and issues it.
    notificationManager.notify(mNotificationId, mBuilder.build());
}