将CALayer阴影从正方形设置为圆形（或圆角）

Question

我有一个UIImageView，它使用以下代码从正方形到圆形动画：

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

我还有一个单独的UIView（它的backgroundColor是clearColor），我专门用它来实现一个动画阴影。除了形状动画外，一切都很好动画：

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;

简而言之，在早上宿醉时，看起来比我看起来更丑。

我想要实现一个漂亮，流畅的圆角动画。知道怎么做？

Answer 1

关键是要使用这些方法：

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
}

在此处找到：iOS animate/morph shape from circle to square