iOS 购物车动画

动画效果：

效果图

Demo

一、计算动画开始结束位置

方法：- (CGPoint)convertPoint:(CGPoint)point toView:(nullable UIView *)view;

1） 动画开始位置fromCenter

CGPoint fromCenter =  [animationView convertPoint:CGPointMake(animationView.frame.size.width * 0.5f, animationView.frame.size.height * 0.5f) toView:keyWindow];

2）动画结束位置endCenter

CGPoint endCenter = [endView convertPoint:CGPointMake(endView.frame.size.width * 0.5f, endView.frame.size.height * 0.5f) toView:keyWindow];

二、计算贝塞尔曲线（抛物线）的两个控制点

图1

• controlPoint1是控制点1
• controlPoint2是控制点2
• A是controlPoint1和controlPoint2的中点
• controlPointC是fromCenter和B的中点

1）先设置控制点距最高点（fromCenter或endCenter）的水平距离controlPointEY，本篇默认controlPointEY = 100，即图1中点controlPointC到点A的距离。

2）计算控制点相对于点A的距离controlPointEX，即controlPoint1到A距离或controlPoint2到A距离，本篇设置为fromCenter.x到endCenter.x的1/4，即controlPointEX = (endCenter.x - fromCenter.x) * 0.25f;

3）计算两个控制点

CGPoint controlPoint1 = CGPointMake(controlPointCX - controlPointEX, controlPointCY - controlPointEY);
CGPoint controlPoint2 = CGPointMake(controlPointCX + controlPointEX, controlPointCY - controlPointEY);

三、复制动画的layer

NSString *str = ((UIButton *)animationView).titleLabel.text;
_animationLayer = [CATextLayer layer];
_animationLayer.bounds = animationView.bounds;
_animationLayer.position = fromCenter;
_animationLayer.alignmentMode = kCAAlignmentCenter;//文字对齐方式
_animationLayer.wrapped = YES;
_animationLayer.contentsScale = [UIScreen mainScreen].scale;
_animationLayer.string = str;
_animationLayer.backgroundColor = [UIColor redColor].CGColor;
[keyWindow.layer addSublayer:_animationLayer];

四、动画组合

1）运动轨迹（抛物线）

UIBezierPath *path = [UIBezierPath bezierPath];
[path moveToPoint:fromCenter];
[path addCurveToPoint:endCenter controlPoint1:controlPoint1 controlPoint2:controlPoint2];
CAKeyframeAnimation *pathAnimation = [CAKeyframeAnimation animationWithKeyPath:@"position"];
pathAnimation.path = path.CGPath;

2）旋转起来

CABasicAnimation *rotateAnimation = [CABasicAnimation animationWithKeyPath:@"transform.rotation"];
rotateAnimation.removedOnCompletion = YES;
rotateAnimation.fromValue = [NSNumber numberWithFloat:0];
rotateAnimation.toValue = [NSNumber numberWithFloat:10 * M_PI];
rotateAnimation.timingFunction=[CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn]

3）缩放动画

CABasicAnimation *scaleAnimation = [CABasicAnimation animationWithKeyPath:@"transform.scale"];
scaleAnimation.removedOnCompletion = NO;
scaleAnimation.fromValue = [NSNumber numberWithFloat:1.0];
scaleAnimation.toValue = [NSNumber numberWithFloat:0.2];

4）透明度动画

CABasicAnimation *alphaAnimation = [CABasicAnimation animationWithKeyPath:@"opacity"];
alphaAnimation.removedOnCompletion = NO;
alphaAnimation.fromValue = [NSNumber numberWithFloat:1.0];
alphaAnimation.toValue = [NSNumber numberWithFloat:0.1];

5）动画组合

CAAnimationGroup *groups = [CAAnimationGroup animation];
groups.animations = @[pathAnimation,rotateAnimation, scaleAnimation, alphaAnimation];
groups.duration = kShoppingCartDuration;
groups.removedOnCompletion=NO;
groups.fillMode=kCAFillModeForwards;
groups.delegate = self;
[_animationLayer addAnimation:groups forKey:@"group"];

五、其他

模拟贝塞尔曲线

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参考：iOS 一分钟搞定加入购物车的交互动画