public int onStartCommand(Intent intent, int flags, int startId) {


    Intent notificationIntent = new Intent(this, NotificationActivity.class);
    PendingIntent pendingIntent =
            PendingIntent.getActivity(this, 0, notificationIntent, 0);
    String id = "mNotification";
    Notification notification = null;
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
        notification = new Notification.Builder(this,id)
                .setContentTitle("getSignalStrength")
                .setContentText("我是信号检测软件,请不要关闭我")
                .setLargeIcon(BitmapFactory.decodeResource(this.getResources(), R.drawable.icon))
                .setSmallIcon(R.drawable.ic_baseline_event_note_24)
                .setContentIntent(pendingIntent)
                .build();
    }

    // Notification ID cannot be 0.
    startForeground(110, notification);
    return super.onStartCommand(intent, flags, startId);
}