如何使用pop或CoreAnimation更改动画的起点或锚点

Question

下面的代码启动一个缩放动画，并从UIButton的中心沿XY扩展。 如何使其从左侧开始或frame.origin.x = 0

    POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerBounds];
    anim.fromValue = [NSValue valueWithCGRect:CGRectMake(signupButton.frame.origin.x,
                                                         signupButton.frame.origin.y,
                                                         0,
                                                         signupButton.frame.size.height)];
    anim.toValue = [NSValue valueWithCGRect:signupButton.frame];
    [anim setValue:@"progressBar" forKey:@"animName"];
    anim.delegate = self;

//    I tried to set anchor point but without any luck
//    signupButton.layer.anchorPoint = CGPointMake(150, signupButton.frame.origin.y);

    [signupButton.layer pop_addAnimation:anim forKey:@"signupButton"];

Answer 1

您正在为边界设置动画，但正在传递帧。 您想动画边界是正确的。

因此，我认为这将是正确的代码。

POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerBounds];
CGRect startRect = signupButton.layer.bounds;
startRect.size.width = 0.0;
anim.fromValue = [NSValue valueWithCGRect:startRect];
anim.toValue = [NSValue valueWithCGRect:signupButton.layer.bounds];
[anim setValue:@"progressBar" forKey:@"animName"];
anim.delegate = self;

//anchor on the center left
CGPoint center = signupButton.layer.position;
signupButton.layer.anchorPoint = CGPointMake(0, 0.5);
signupButton.layer.position = CGPointMake(center.x - signupButton.layer.bounds.size.width * 0.5, center.y);

[signupButton.layer pop_addAnimation:anim forKey:@"signupButton"];