UIView is shown after IBAction method returns

Question

I've got the following code fragment (for illustration purpose):

- (IBAction)buttonPress:(id)sender {
    UIView *overlayView = [[UIView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    overlayView.backgroundColor = [UIColor colorWithRed:0 green:0 blue:0 alpha:0.5];
    UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];
    activityIndicator.center = overlayView.center;
    [overlayView addSubview:activityIndicator];
    [self.navigationController.view addSubview:overlayView];
    //[self.navigationController.view bringSubviewToFront:overlayView];
    [activityIndicator startAnimating];

    sleep(10);

    //[overlayView removeFromSuperview];
}

I wonder why the overlay view is only displayed after the method returns...

from where returns – Prashant Tukadiya Aug 06 '16 at 08:34 — Prashant Tukadiya, Aug 06 '16 at 08:34

score 0 · Accepted Answer · edited May 23 '17 at 11:51

0

I guess it's because sleep(10) blocks the main thread which is responsible for performing UI related activities, such as drawing on screen.

Remove the sleep(10) line and should work fine.

Here's on link to SO in case you're interested how to use delays in coca-touch:
Adding delay between execution of two following lines

edited May 23 '17 at 11:51

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answered Aug 06 '16 at 09:14

Andrej

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Right... Then it's a bad idea to use synchronous operations within the method. – Andrew Aug 06 '16 at 09:27

UIView is shown after IBAction method returns

1 Answers1