动画的CALayer阴影圆圈（或圆角）

Question

我有一个UIImageView，它从正方形动画来圈与此代码：

CABasicAnimation *circleShapeAnimation = [CABasicAnimation animationWithKeyPath:@"cornerRadius"]; 
circleShapeAnimation.fromValue = [NSNumber numberWithFloat:0.0f]; 
circleShapeAnimation.toValue = [NSNumber numberWithFloat:cornerRadius]; 

我也有一个单独的的UIView（其的backgroundColor是clearColor），我专门用来实现动画阴影。动画一切正常，除了形状动画：

CABasicAnimation* shadowShapeAnimation = [CABasicAnimation animationWithKeyPath: @"shadowPath"]; 
shadowShapeAnimation.fromValue = (id)[UIBezierPath bezierPathWithRoundedRect: cell.placeImage.bounds cornerRadius:0.0f].CGPath; 
shadowShapeAnimation.toValue = (id)[UIBezierPath bezierPathWithRoundedRect: cell.placeImage.bounds cornerRadius:cornerRadius].CGPath; 

其中，简单地说，看起来比我早上宿醉丑陋。

我想实现圆角的一个不错的，流畅的动画效果。任何想法如何？

Answer 1

的关键是使用这些方法：

func circlePathWithCenter(center: CGPoint, radius: CGFloat) -> UIBezierPath { 
    let circlePath = UIBezierPath() 
    circlePath.addArcWithCenter(center, radius: radius, startAngle: -CGFloat(M_PI), endAngle: -CGFloat(M_PI/2), clockwise: true) 
    circlePath.addArcWithCenter(center, radius: radius, startAngle: -CGFloat(M_PI/2), endAngle: 0, clockwise: true) 
    circlePath.addArcWithCenter(center, radius: radius, startAngle: 0, endAngle: CGFloat(M_PI/2), clockwise: true) 
    circlePath.addArcWithCenter(center, radius: radius, startAngle: CGFloat(M_PI/2), endAngle: CGFloat(M_PI), clockwise: true) 
    circlePath.closePath() 
    return circlePath 
} 

func squarePathWithCenter(center: CGPoint, side: CGFloat) -> UIBezierPath { 
    let squarePath = UIBezierPath() 
    let startX = center.x - side/2 
    let startY = center.y - side/2 
    squarePath.moveToPoint(CGPoint(x: startX, y: startY)) 
    squarePath.addLineToPoint(squarePath.currentPoint) 
    squarePath.addLineToPoint(CGPoint(x: startX + side, y: startY)) 
    squarePath.addLineToPoint(squarePath.currentPoint) 
    squarePath.addLineToPoint(CGPoint(x: startX + side, y: startY + side)) 
    squarePath.addLineToPoint(squarePath.currentPoint) 
    squarePath.addLineToPoint(CGPoint(x: startX, y: startY + side)) 
    squarePath.addLineToPoint(squarePath.currentPoint) 
    squarePath.closePath() 
    return squarePath 
} 

这里找到：iOS animate/morph shape from circle to square