Reload navigationBar UIBarButtonItems

Question

I've been trying to solve this issue, but I can't figure out how.

I have a UIButton to which I need to add a UILabel as a subview.

I need to update this UIButton because I don't have the number I need until a method is called through an NSNotification.

The thing is, with this code theUIBarButtonItem takes too long to change, and if the UITableView is scrolled (navBar disappears) both buttons disappear (even though the navigationBar reappears).

- (void) addSettingsButton {
    self.navigationItem.rightBarButtonItems = nil;

    UIButton * button2 = [UIButton buttonWithType:UIButtonTypeSystem];
    button2.frame = CGRectMake(0, 0, 19, 19);
    [button2 setImage:[UIImage imageNamed:@"settingsBtn.png"] forState:UIControlStateNormal];
    button2.tintColor = [UIColor grayColor];
    [button2 addTarget:self action:@selector(showSettings) forControlEvents:UIControlEventTouchUpInside];
    //self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithCustomView:button2];
    UIBarButtonItem* button2Aux = [[UIBarButtonItem alloc] initWithCustomView:button2];

    UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 19, 19)];

    UIButton * button3 = [UIButton buttonWithType:UIButtonTypeSystem];
    button3.frame = CGRectMake(0, 4, 23, 15.5);

    int altoPantalla = [UIScreen mainScreen].bounds.size.height;

    [button3 setBackgroundImage:[UIImage imageNamed:[NSString stringWithFormat:@"Icon_Buzon.png"]] forState:UIControlStateNormal];

    [button3 addTarget:self action:@selector(showTut) forControlEvents:UIControlEventTouchUpInside];

    [view addSubview:button3];

    NSString *cantNotificaciones = self.cantNotificaciones;
    NSInteger posX = 0, posY = 0, ancho = 0, alto = 0, radio;
    BOOL ponerCirculo = NO;

    if (cantNotificaciones.length >= 3) {

        cantNotificaciones = @"+99";
        posX = 10.5;
        posY = 12;
        ancho = 21;
        alto = 15;
        radio = 8;
        ponerCirculo = YES;

    } else if (cantNotificaciones.length == 2 || (cantNotificaciones.length == 1 && ![cantNotificaciones isEqualToString:@"0"])) {

        posX = 8;
        posY = 12;
        ancho = 16;
        alto = 16;
        radio = 8;

        ponerCirculo = YES;
    } else {
        ponerCirculo = NO;
    }

    if (ponerCirculo) {

        UILabel *lbl3 = [[UILabel alloc] initWithFrame:CGRectMake(button3.center.x-posX, -posY, ancho, alto)];
        [lbl3 setText:cantNotificaciones];
        lbl3.textColor = [UIColor whiteColor];
        lbl3.backgroundColor = [UIColor redColor];
        [lbl3 setFont:[UIFont systemFontOfSize:10]];
        lbl3.layer.cornerRadius = radio;
        lbl3.clipsToBounds = YES;
        [lbl3 setTextAlignment:NSTextAlignmentCenter];
        [button3 addSubview:lbl3];

    } else {

    }

    UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(showTut)];
    [tap setNumberOfTouchesRequired:1];
    [tap setNumberOfTapsRequired:1];
    [view addGestureRecognizer:tap];

    UIBarButtonItem* button3Aux = [[UIBarButtonItem alloc] initWithCustomView:view];

    switch (altoPantalla) {
        case 480:
            posicionX = -7;
            space = 21;
            break;
        case 568:
            posicionX = -10;
            space = 21;
            break;
        case 667:
            posicionX = 19;
            space = 27;
            break;
        case 736:
            posicionX = 19;
            space = 40;
            break;
        default:
            break;
    }

    UIBarButtonItem *positiveSpacer = [[UIBarButtonItem alloc]
                                   initWithBarButtonSystemItem:UIBarButtonSystemItemFixedSpace
                                   target:nil action:nil];
    positiveSpacer.width = space;

    self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:button2Aux, positiveSpacer, button3Aux, nil];
    [self.view setNeedsLayout];
    [self.view setNeedsDisplay];
}

-(void) modificarNumeroBoton:(NSNotification *) notification
{
    NSString *cantidad = (NSString *)[notification object];
    NSLog(@"Numero recibido: %@",cantidad);

    self.cantNotificaciones = cantidad;
    [self addSettingsButton];
}

For me there's two possible solutions: Either make the update immediate (would be better), or make it so the buttons don't disappear when scrolled

Answer 1

If you want to reload the label text or the table view then do it on the Main thread.

Notifications work on threads other than main unless specified.

Do this:

dispatch_async(dispatch_get_main_queue(), ^(void){
        //Update the label text
        // Update the Tableview
});