Objective-C Block stops UIGestureRecognizer - iphone

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.

Answer 2

This is because, when UIView is animating using blocks it prevents UI interaction. To avoid this behaviour you must use the UIViewAnimationOptionAllowUserInteraction option:
[UIView animateWithDuration:1
delay:0.0
options:UIViewAnimationOptionAllowUserInteraction
animations:^{
readyLabel.alpha = 0;
}
completion:^(BOOL finished){
[UIView animateWithDuration:1
delay:0.0
options:UIViewAnimationOptionAllowUserInteraction
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];
}
];
}
];