iphone - How to pause and resume UIView Animation?

Question

I have a UIView with several UILabels that is animating from top to bottom and vice versa. A sort of Autoque let's say :) I use 2 functions:

-(void)goUp 
-(void)goDown 

Those functions start a UIView animation to the required position.They both have an AnimationDidStopSelector defined that calls the other function at the end. This all works smoothly.

When touching the screen, using touchesBegan, I would like to pause the current animation and change the vertical position of the UIView using touchesMoved event. In touchesEnded I want to resume the animation to the required end position.

What would be the proper way to do so?

Thomas

Answer 1

I've created a category on UIView to pause and stop animations:

@interface UIView (AnimationsHandler)

- (void)pauseAnimations;
- (void)resumeAnimations;

@end

@implementation UIView (AnimationsHandler)
- (void)pauseAnimations
{
    CFTimeInterval paused_time = [self.layer convertTime:CACurrentMediaTime() fromLayer:nil];
    self.layer.speed = 0.0;
    self.layer.timeOffset = paused_time;
}

- (void)resumeAnimations
{
    CFTimeInterval paused_time = [self.layer timeOffset];
    self.layer.speed = 1.0f;
    self.layer.timeOffset = 0.0f;
    self.layer.beginTime = 0.0f;
    CFTimeInterval time_since_pause = [self.layer convertTime:CACurrentMediaTime() fromLayer:nil] - paused_time;
    self.layer.beginTime = time_since_pause;
}