CALayer - CABasicAnimation not scaling around center/anchorPoint

ios core-animation
spring picture spring · Jul 15, 2012 · Viewed 18.3k times · Source

Using the code below I've been trying to get my CALayer to scale around its center - but it scales by left/top (0,0). I saw this question: Anchor Point in CALayer and have tried setting the anchorPoint - but it was [.5, .5] before I set it and setting makes no difference. Also tried setting contentsGravity.

The set up is I have a CAShapeLayer added to self.view.layer I do some drawing in it and then add the CABasicAnimation. The animation runs fine - but it scales toward the top/left - not the center of the view.

Have been tinkering with this for a few hours - it must be something simple but I'm not getting it.

shapeLayer.anchorPoint = CGPointMake(.5,.5);
shapeLayer.contentsGravity = @"center";

printf("anchorPoint %f  %f\n", shapeLayer.anchorPoint.x, shapeLayer.anchorPoint.y);

CABasicAnimation *animation =
[CABasicAnimation animationWithKeyPath:@"transform.scale"];

animation.fromValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
animation.toValue =   [NSValue valueWithCATransform3D:CATransform3DMakeScale(0.1, 0.1, 1.0)];

[animation setDuration:1.0];
animation.fillMode=kCAFillModeForwards;
animation.removedOnCompletion=NO;
[shapeLayer addAnimation:animation forKey:@"zoom"];

Answer

Kurt Revis picture Kurt Revis · Jul 16, 2012

What is the bounds of your layer?

I bet it has zero size; try setting its size to the same size as your shape.

CAShapeLayer draws the shape as kind of an overlay, independent of the contents (and bounds and contentsGravity and etc.) that you'd use in an ordinary CALayer. It can be a bit confusing.

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