Question

Here is my problem.

I use blocks to display two labels on screen one by one (one READY label appears, then disappears, and GO! label appears, then disappears).

I also have a gesture recognizer to detect if the user is dragging a view.

When my app is displaying the labels, gesture recognizers stop calling their callback.

Here is my code:

[UIView animateWithDuration:1 animations:^{
    readyLabel.alpha = 0;
}completion:^(BOOL finished){
    [readyLabel removeFromSuperview];
    [self.view addSubview:goLabel];
    [UIView animateWithDuration:1 animations:^{
        goLabel.alpha = 0;
    }completion:^(BOOL finished){
        self.ball = [[Ball alloc] init];
        [self.view addSubview:self.ball];

        _timer = [NSTimer scheduledTimerWithTimeInterval:0.02 target:self selector:@selector(moveBall:) userInfo:nil repeats:YES];
    }];
}];

What I tried so far is using NSThread to execute my blocks outside of the main thread, but without result.

I could use performSelector:withObject:afterDelay to avoid the problem for my labels (display one label after the first animation has finished) but I think it’s a bit dirty.

Why does my gesture recognizer stop calling his callback? Are blocks responsible for this?

Answer 1

This is because block animations disable user interaction. You should use animateWithDuration:delay:options:animations:completion: and specify UIViewAnimationOptionAllowUserInteraction in options.