startForeground()不显示任何通知

private void createNotificationChannel() {
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        CharSequence name = "My Foreground Service";
        String description = "My Foreground Service Description";
        int importance = NotificationManager.IMPORTANCE_LOW;
        NotificationChannel channel = new NotificationChannel("my_foreground_service_channel", name, importance);
        channel.setDescription(description);
        NotificationManager notificationManager = getSystemService(NotificationManager.class);
        notificationManager.createNotificationChannel(channel);
    }
}

private Notification createNotification() {
    Intent notificationIntent = new Intent(this, MainActivity.class);
    PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);

    NotificationCompat.Builder builder = new NotificationCompat.Builder(this, "my_foreground_service_channel")
            .setSmallIcon(R.drawable.ic_notification)
            .setContentTitle("My Foreground Service")
            .setContentText("My Foreground Service is running...")
            .setContentIntent(pendingIntent);

    return builder.build();
}

@Override
public void onCreate() {
    super.onCreate();
    createNotificationChannel();
    Notification notification = createNotification();
    startForeground(1, notification);
}