如何在一个点旋转CALayer

Question

如何在一个选定点旋转CALayer。

Answer 1

CATransform3D transform = CATransform3DIdentity;
transform = CATransform3DTranslate(transform, rotationPoint.x-center.x, rotationPoint.y-center.y, 0.0);
transform = CATransform3DRotate(transform, rotationAngle, 0.0, 0.0, -1.0);
transform = CATransform3DTranslate(transform, center.x-rotationPoint.x, center.y-rotationPoint.y, 0.0);

center是图层的中心，rotationAngle以弧度为单位（正向为逆时针方向），rotationPoint是您想要旋转的点。 center和rotationPoint位于包含视图的坐标空间中。

Answer 2

1. 定义要旋转的子图层;
2. 在超级层和bounds中设置其position，anchorPoint。 anchorPoint具有相对坐标并指向anchorPoint。您的子图层将围绕此anchorPoint;
旋转
3. 添加转化。

例如，要在子图层底部中心周围的超视图顶部中心点旋转子图层，请使用以下代码：

    // 1
    let rect = CGRect(x: 0,
                      y: 0,
                      width: 20,
                      height: 20)
    let path = UIBezierPath(rect: rect)
    let sublayer = CAShapeLayer()
    sublayer.fillColor = UIColor.green.cgColor
    sublayer.path = path.cgPath
    superlayer.addSublayer(sublayer)

    // 2
    sublayer.bounds = rect
    sublayer.position = CGPoint(x: superlayer.bounds.size.width/2, y: 0)
    sublayer.anchorPoint = CGPoint(x: 0.5, y: 1)

    // 3
    let rotationAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
    rotationAnimation.toValue = 2*CGFloat.pi
    rotationAnimation.duration = 3
    rotationAnimation.fillMode = kCAFillModeForwards
    rotationAnimation.isRemovedOnCompletion = false
    sublayer.add(rotationAnimation, forKey: nil)

Answer 3

查看CA文档here。

您希望将变换设置为CATransform3DRotate，例如：

CATransform3D current = myLayer.transform;
myLayer.transform = CATransform3DRotate(current, DEGREES_TO_RADIANS(20), 0, 1.0, 0);