How do you animate the sublayers of the layer of a UIView during a UIView animation?

Question

In a UIView animation for a view, you can animate its subviews being laid out by including UIViewAnimationOptionLayoutSubviews in the options parameter

Answer 1

You might have found the answer already, but I also faced similar problems recently, since solved it, I will post the answer.

In - layoutSubViews method, you can get current UIView animation as backing layer's CAAnimation with - animationForKey: method. Using this, You can implement - layoutSubviews like:

- (void)layoutSubviews {
    [super layoutSubviews];

    // get current animation for bounds
    CAAnimation *anim = [self.layer animationForKey:@"bounds"];

    [CATransaction begin];
    if(anim) {
        // animating, apply same duration and timing function.
        [CATransaction setAnimationDuration:anim.duration];
        [CATransaction setAnimationTimingFunction:anim.timingFunction];

        CABasicAnimation *pathAnimation = [CABasicAnimation animationWithKeyPath:@"path"];
        [self.borderLayer addAnimation:pathAnimation forKey:@"path"];
    }
    else {
        // not animating, we should disable implicit animations.
        [CATransaction disableActions];
    }

    self.borderLayer.path = [UIBezierPath bezierPathWithRect:self.bounds].CGPath;
    self.borderLayer.frame = self.bounds;
    [CATransaction commit];
}