UIView animation block pause both the animation and the completion code

Question

I have an animation block to perform a simple transform based animation, that on completion removes the view in question from its superview.

UIView *msgView = [[UIView alloc] initWithFrame:CGRectMake(160, 120, 160, 100)];

// Do stuff to set up the subviews of msgView.

// Add the msgView to the superview (ViewController) that is going to display it.

CATransform3D transform = CATransform3DMakeScale(2.5, 2.5, 1.0);

[UIView animateWithDuration:5.0 
                 animations:^(void){msgView.layer.transform = transform;}
                 completion:^(BOOL finished){[msgView removeFromSuperview];}];

I then use the code as detailed by Tech Q&A 1673 http://developer.apple.com/library/ios/#qa/qa1673/_index.html to pause the animation.

-(void)pauseLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
    layer.speed = 0.0;
    layer.timeOffset = pausedTime;
}

-(void)resumeLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer timeOffset];
    layer.speed = 1.0;
    layer.timeOffset = 0.0;
    layer.beginTime = 0.0;
    CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
    layer.beginTime = timeSincePause;
}

However, this code does not prevent the completion code from executing. So to prevent the code from executing I change the code for completion to this:

completion:^(BOOL finished){if(finished == TRUE)[msgView removeFromSuperview];};

Whilst checking for finished == TRUE prevents the completion code from being executed whilst the animation block is paused. If the duration time is now exceded before you "unpause" the animation, the completion code will not be executed. ie In this case the msgView remains in the superview.

Is there anyway to pause/unpause both the animation and the timer associated with the completion code (if that's what's going on)?

Answer 1

As I said in the comments above, there doesn't seem to be a problem. The below is tested in iOS 5.1 and 6.1.

Create a storyboard with UIImageView *transView and UIButton *trigger. Here's the class:

TSTViewController.h:

@property (weak, nonatomic) IBOutlet UIImageView *transView;
@property (weak, nonatomic) IBOutlet UIButton *trigger;
@property (nonatomic) NSUInteger bState;

- (IBAction)didPressTrigger:(id)sender;

TSTViewController.m:

- (void)viewDidLoad
{
    [super viewDidLoad];
    self.bState = 0;    // 0 is initial state
                        // 1 is transform being animated
                        // 2 is transform paused
                        // 3 is transform ended
}

- (IBAction)didPressTrigger:(id)sender {
    switch (self.bState) {
        case 0:
        {
            CATransform3D transform = CATransform3DMakeScale(2.5, 2.5, 1.0);
            self.bState++;
            [UIView animateWithDuration:5.0
                             animations:^(void){self.transView.layer.transform = transform;}
                             completion:^(BOOL finished){
                                 self.bState = 3;
                                 NSLog(@"Done");
                             }];
            break;
        }
        case 1:
        {
            self.bState++;
            [self pauseLayer:self.transView.layer];
            break;
        }
        case 2:
        {
            self.bState = 1;
            [self resumeLayer:self.transView.layer];
            break;
        }
        case 3:
        {
            [UIView animateWithDuration:0 animations:^(void){self.transView.layer.transform = CATransform3DIdentity;}
                             completion:^(BOOL finished) {
                                 self.bState = 0;
                                 NSLog(@"Reset");
                             }];
            break;
        }
        default:
            break;
    }
}

-(void)pauseLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer convertTime:CACurrentMediaTime() fromLayer:nil];
    layer.speed = 0.0;
    layer.timeOffset = pausedTime;
}

-(void)resumeLayer:(CALayer*)layer
{
    CFTimeInterval pausedTime = [layer timeOffset];
    layer.speed = 1.0;
    layer.timeOffset = 0.0;
    layer.beginTime = 0.0;
    CFTimeInterval timeSincePause = [layer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
    layer.beginTime = timeSincePause;
}

When you press the trigger button, the animation starts. Press it again, the animation stops. Wait 10 seconds, and press the button yet again. The animation continues and finishes, and it logs "Done".