Animating CAShapeLayer size change

Question

I am drawing a circle, with an initial radius of 200

self.circle = [CAShapeLayer layer];
self.circle.fillColor = nil;
self.circle.strokeColor = [UIColor blac         


        

Answer 1

You can use a CAAnimationGroup to animate the bounds and path of your CAShapeLayer:

- (void)animateToRadius:(CGFloat)newRadius {
   CAShapeLayer *shapeLayer = ...;

   UIBezierPath *newBezierPath = [UIBezierPath bezierPathWithArcCenter:CGPointMake(newRadius, newRadius)];
   NSValue *newBounds = [NSValue valueWithCGRect:CGRectMake(0,0,2*newRadius,2*newRadius);

   CAAnimationGroup *group = [CAAnimationGroup animation];

   NSMutableArray *animations  = [@[] mutableCopy];
   NSDictionary *animationData = @{@"path":newBezierPath.CGPath, @"bounds":newBounds};
   for(NSString *keyPath in animationData) {
      CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:keyPath];
      animation.toValue   = animationData[keyPath];
      [animations addObject:animation];
   }

   group.animations = [animations copy];
   group.duration = 2;
   group.removedOnCompletion = NO;
   group.fillMode = kCAFillModeForwards;

   [shapeLayer addAnimation:group forKey:nil];
}