ios - 如何围绕左上角的点旋转图像？

Question

我有一个音乐播放器，我希望播放器播放时针头图像在磁盘上。在播放器未播放时将图像围绕左上角点旋转 45°。needleImgView 的约束是 centerX to superView, top to superview = 40, size = (97,153)

我用谷歌搜索并找到了以下代码:

func setAnchorPoint(_ anchorPoint:CGPoint, for view:UIView){

        let oldOrigin = view.frame.origin
        view.layer.anchorPoint = anchorPoint
        let newOrigin = view.frame.origin

        var transition = CGPoint()
        transition.x = newOrigin.x - oldOrigin.x
        transition.y = newOrigin.y - oldOrigin.y
        view.center = CGPoint(x: view.center.x - transition.x, y: view.center.y - transition.y)

    }

然后用下面的方法旋转图片:

if !player.isPlaying {
        setAnchorPoint(CGPoint(x:40 / 97.0,y:40 / 153.0), for: needleImgView) // I'm NOT SURE the 40 is right.
        //needleImgView.layer.anchorPoint = CGPoint(x:0,y:0)
        UIView.animate(withDuration: 0.5, animations: {
            self.needleImgView.transform = CGAffineTransform(rotationAngle: CGFloat(-Double.pi / 4))
        }, completion: nil)

    }else{
        setAnchorPoint(CGPoint(x:40 / 97.0,y:40 / 153.0), for: needleImgView) 
        //needleImgView.layer.anchorPoint = CGPoint(x:0,y:0)
        UIView.animate(withDuration: 0.5, animations: {
            self.needleImgView.transform = .identity
        }, completion: nil)

    }

我设置了 setAnchorPoint(CGPoint(x:0/97.0,y:0/153.0), for: needleImgView) 或 needleImgView.layer.anchorPoint = CGPoint(x:0,y :0),结果是左上角的点也移开了。

如何解决？谢谢。

Answer 1

你可以尝试CABasicAnimation。

anchor x的0.5表示在宽度的中间，y的0表示高度的顶部。

    imageView.layer.anchorPoint = CGPoint.init(x: 0.5, y: 0)

    let basic = CABasicAnimation.init(keyPath: "transform.rotation")
    basic.fromValue = NSNumber.init(value: 0)
    basic.toValue = NSNumber.init(value: -(Double.pi / 4))
    basic.fillMode = kCAFillModeForwards
    basic.isRemovedOnCompletion = false
    imageView.layer.add(basic, forKey: nil)