UITapGestures in Middle of Animations

Question

I'm am trying to delete an image while it is moving on the screen using UITapGestureRecognizers and UIViewAnimation. I have used the UIViewAnimationOptionAllowUserInteraction, but I still get the SIGBART error. I have been looking through the internet and couldn't find a solution.

This is my .m file

#import "AbcViewController.h"


@interface AbcViewController ()

@end

@implementation AbcViewController

//single tap gesture action /deletes person
-(void) tapped:(UITapGestureRecognizer *)recognizer{
   [recognizer.view removeFromSuperview];
}

    //double tap gesture action
-(void) tapped2:(UITapGestureRecognizer *)recognizer{
[recognizer.view removeFromSuperview];
}

- (void)viewDidLoad
{



   [super viewDidLoad];

//this makes a zombie/person
UIImageView *zombieView =[[UIImageView alloc] initWithFrame:CGRectMake(135 , 300, 50, 75)];
UIImage *zombie=[UIImage imageNamed:@"free-vector-stick-figure-clip-art_105575_Stick_Figure_clip_art_hight.png"];
[zombieView setImage:zombie];
[self.view addSubview:zombieView];
[self.view insertSubview:zombieView belowSubview:_Railing];
[zombieView setUserInteractionEnabled:TRUE];

// double tap gesture recognizer
UITapGestureRecognizer *touch2 = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped2:)];
[touch2 setDelegate: self];
[touch2 setNumberOfTapsRequired: 2];
[zombieView addGestureRecognizer:touch2];

//tap gesture recognizer
UITapGestureRecognizer *touch = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tapped:)];
[touch setDelegate:self];
[touch setNumberOfTapsRequired: 1];
[zombieView addGestureRecognizer:touch];

//This makes the Person move down until he is behind the railing
[UIView animateWithDuration:8.5
                    delay:0.0
                    options:UIViewAnimationOptionAllowUserInteraction | UIViewAnimationOptionCurveLinear
                    animations:^{
                    CGAffineTransform transform= CGAffineTransformMakeTranslation(0,-200);
                    zombieView.transform = transform;
                   }
                 completion:nil];


};


-(void)didReceiveMemoryWarning
{

    [super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}

@end 

This is my .h file:

#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>

@interface AbcViewController : UIViewController <UIGestureRecognizerDelegate>

@property (strong, nonatomic) IBOutlet UIImageView *Railing;
//@property (strong, nonatomic) IBOutlet UIImageView *Person;
@property (strong, nonatomic) IBOutlet UIImageView *zombieView;
@property (strong, nonatomic) IBOutlet UIImage *zombie;

-(void) tapped:(UITapGestureRecognizer *)recognizer;
-(void) tapped2:(UITapGestureRecognizer *)recognizer;

@end

Every time I click it in mid-animation I get an error but when it's complete it works fine. I am fairly new to this so I'm sure it's simple, it always is. But, thank you for your patience and answers!

Answer 1

The object during the animation is not where you see it. It has already moved to its final position. Animation is an illusion: the "presentation layer" is animated, but the underlying "model layer" (the real object) stands still and has already moved when the animation starts. The model layer is the one inside a view so it is the only one that can be tapped.

Tapping an object while it is being animated is therefore a very tricky problem. I discuss it here:

http://www.apeth.com/iOSBook/ch18.html#_hit_testing_during_animation

Perhaps that discussion will give you some ideas. But no matter what, this is not going to be easy.

(Consider that perhaps you should not be using view animation for this kind of game. Sprite Kit was invented for just this sort of thing.)