如何在一個點上旋轉CALayer

Question

如何在一個選定點上旋轉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); 

哪裏center是您層的中心，rotationAngle是弧度（正面是逆時針），並且rotationPoint是點你想旋轉。 center和rotationPoint位於包含視圖的座標空間中。

Answer 2

查看CA文檔here。

你想設置的轉換爲CATransform3DRotate，例如：

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

Answer 3

1. 定義要旋轉你的子層;
2. 設置它的bounds,position在超級層和anchorPoint。 anchorPoint有相對座標並且指向anchorPoint。您的子圖層將圍繞此旋轉anchorPoint;
3. 添加轉換。

例如，爲了對圍繞子層的底部中心它的父頂部中心點旋轉的子層，使用以下代碼：

// 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)