Display activity indicator over dimmed screen

dimScreenAndShowActivityIndicator.m

- (IBAction)dimScreenAndShowActivityIndicator:(id)sender {
    CGRect bounds = self.view.bounds;
    
    // Create black view covering entire view
    UIView *maskView = [[UIView alloc] initWithFrame:bounds];
    maskView.backgroundColor = [UIColor blackColor];    
    [self.view addSubview:maskView];
    
    // Put spinning activity indicator in middle of view
    UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithActivityIndicatorStyle:UIActivityIndicatorViewStyleWhiteLarge];
    activityIndicator.frame = bounds;
    [maskView addSubview:activityIndicator];
    [activityIndicator startAnimating];
    
    // Put a label below the activity indicator
    CGRect statusLabelFrame = CGRectMake(0, 0, 320, 20);
    UILabel *statusLabel = [[UILabel alloc] initWithFrame:statusLabelFrame];
    statusLabel.center = CGPointMake(maskView.center.x, maskView.center.y + 32);
    statusLabel.textColor = [UIColor whiteColor];
    statusLabel.backgroundColor = [UIColor clearColor];
    statusLabel.text = @"Submitting Report";
    statusLabel.textAlignment = NSTextAlignmentCenter;
    statusLabel.font = [UIFont boldSystemFontOfSize:14];
    [maskView addSubview:statusLabel];
    
    // Fade in the screen-covering view
    maskView.alpha = 0.0;
    [UIView animateWithDuration:0.6 animations:^{
        [maskView setAlpha:0.8];
    }];
    
    // After delay, fade the view out and remove it
    int64_t delayInSeconds = 2.0;
    dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);
    dispatch_after(popTime, dispatch_get_main_queue(), ^(void){
        [activityIndicator stopAnimating];
        statusLabel.text = @"";
        [UIView animateWithDuration:0.6
                         animations:^{
                             [maskView setAlpha:0];
                         } completion:^(BOOL finished) {
                             [maskView removeFromSuperview];
                         }];
    });
}