CAKeyframeAnimation Manual Progress

Question

I have a UIView whose backing layer has a CAKeyframeAnimation with a simple straight line path set as its `path`.
Can I have the animation \"frozen\", so to speak, and man

Answer 1

Yes you can do this with the CAMediaTiming interface. You can set the speed of the layer to 0 and manualy set the timeOffset. Example of a simple pause/resume method:

- (void)pauseAnimation {
    CFTimeInterval pausedTime = [yourLayer convertTime:CACurrentMediaTime() fromLayer:nil];
    yourLayer.speed = 0.0;
    yourLayer.timeOffset = pausedTime;
}

- (void)resumeAnimation {

    CFTimeInterval pausedTime = [yourLaye timeOffset];
    if (pausedTime != 0) {
        yourLayer.speed = 1.0;
        yourLayer.timeOffset = 0.0;
        yourLayer.beginTime = 0.0;

        CFTimeInterval timeSincePause = [yourLayer convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
        yourLayer.beginTime = timeSincePause;
    }
}

Answer 2

This is based on what Jonathan said, only a bit more to the point. The animation is set up correctly, but the slider action method should be as follows:

- (void)sliderDidSlide:(UISlider *)slider 
{
    // Create and configure a new CAKeyframeAnimation instance
    CAKeyframeAnimation *animation = ...;
    animation.duration = 1.0;
    animation.speed = 0;
    animation.removedOnCompletion = NO;
    animation.timeOffset = slider.value;

    // Replace the current animation with a new one having the desired timeOffset
    [_label.layer addAnimation:animation forKey:@"LabelPathAnimation"];
}

This will make the label move along the animation's path based on timeOffset.