UIScrollView: subview added but not showing up

Question

I have a UIScrollView called scroller. It has subviews which are custom UIButtons..I try to print the number of subviews before and after adding like as follows

    NSLog(@"Adding %d b4 %d",buttonno, [[self.scroller subviews] count]);
    [self.scroller addSubview:menuBtn];
    NSLog(@"Adding %d after %d",buttonno, self.scroller.subviews.count);

The subview is not showing up. But the number of subviews increments for example the output of this is like

2014-03-11 17:53:49.863 PC2[4519:60b] Adding 1 b4 10

2014-03-11 17:53:49.872 PC2[4519:60b] Adding 1 after 11

But when I try to print the number of subviews using a test button which runs the code

NSLog(@"Buttons subviews: %d",self.scroller.subviews.count);

I can see that no subview is added..I can also see that no subview is added when I see the variables in the debugger.

btw I'm adding buttons based on timer [NSTimer scheduledTimerWithTimeInterval:0.2 target:self selector:@selector(checkForTiles) userInfo:nil repeats:YES];

Update:: The code to add subview

                if (!alreadyExists)
{
    NSLog(@"Adding %d b4 %d",buttonno, [[self.scroller subviews] count]);
    //AudioServicesPlayAlertSound(kSystemSoundID_Vibrate);
    pccButtonViewController *menuBtn=nil;
    menuBtn=[pccButtonViewController alloc ];
    menuBtn = [pccButtonViewController buttonWithType:UIButtonTypeCustom];
    menuBtn.no=buttonno;
    menuBtn.slotNo=buttonCount;
    menuBtn.frame = [[slotFrames objectAtIndex:menuBtn.slotNo] CGRectValue];
    [menuBtn setBackgroundImage:[UIImage imageNamed:[[NSString alloc] initWithFormat:@"L%02d_Tile.jpg",buttonno]] forState:UIControlStateNormal];
    [menuBtn addTarget:self action:@selector(miniButtons:) forControlEvents:UIControlEventTouchUpInside];
    menuBtn.no=buttonno;
    menuBtn.alpha=0.0f;
    [self.scroller addSubview:menuBtn];
    NSLog(@"Adding %d after %d",buttonno, self.scroller.subviews.count);
    //NSLog(@"Subview Added %d btn no:%@",buttonno,[slotFrames objectAtIndex:menuBtn.slotNo]);
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1.0f];
    //self.menuBtn.frame = CGRectMake(8, 10, 50, 60);
    menuBtn.alpha=1.0f;
    [UIView commitAnimations];
    [buttons addObject:menuBtn];
    buttonCount++;
}
buttonclicked=0;
[self.scroller  setContentSize:CGSizeMake([self.scroller  bounds].size.width,(ceil(buttonCount/tilesPerRow)+1)*[self.scroller  bounds].size.width/tilesPerRow/2*3)];
appdelegate.Sharevar.vidsyncButtons=self.scroller.subviews.copy;//Used to maintain State when the view is presented for the second time

This works fine when the View runs for the first time.The problems arise when it is run for the second time..I remove the view from appdelegate like this

-(void)removeAnyView
{
NSLog(@"Removing");
if (viewonScreen)
{
    viewonScreen=false;
    [self.inPort prepareToBeDeleted];
    self.inPort=Nil;
    [self.window.rootViewController dismissViewControllerAnimated:NO completion:^{[self     presentView];}];
 }

}

Answer 1

It's been a long time.. I forgot about this question.. The error was caused by not invalidating the NSTimer.. Got to be careful with these..

Answer 2

Any updates to the UI have to be on the main thread, which your NSTimer won't be, so you need to do something like this...

dispatch_sync(dispatch_get_main_queue(), ^{
    [self.scroller addSubview:menuBtn];
});

Answer 3

Change this

menuBtn=[pccButtonViewController alloc ];

to this

menuBtn=[[pccButtonViewController alloc ] init];

From documenation:

buttonWithType:

This method is a convenience constructor for creating button objects with specific configurations. If you subclass UIButton, this method does not return an instance of your subclass. If you want to create an instance of a specific subclass, you must alloc/init the button directly.