NSView旋转

一个看似简单的旋转，用了大半天的时间，有必要总结一下。

首先献上网上旋转动画的代码

链接：https://www.jianshu.com/p/f568a55e1f9f
此教程实现了连续旋转，动画结束后，会回到原来的状态，如果我们需要实现图片旋转 90 度的功能就不行了
核心代码：

let oldFrame = imageView.layer!.frame
imageView.wantsLayer = true
let animation = CABasicAnimation.init(keyPath: "transform.rotation")
animation.timingFunction = CAMediaTimingFunction.init(name: CAMediaTimingFunctionName.linear)
animation.fromValue = 0
animation.toValue = CGFloat.pi / 2
animation.duration = 0.5
animation.repeatCount = 1
let cent_x = imageView.frame.origin.x + imageView.frame.size.width/2
let cent_y = imageView.frame.origin.y + imageView.frame.size.height/2
//旋转锚点
imageView.layer?.anchorPoint = CGPoint.init(x: 0.5, y: 0.5)
//旋转位置
imageView.layer?.position = CGPoint.init(x: cent_x, y: cent_y)
imageView.layer?.add(animation, forKey: nil)

代码略作改进

如何实现旋转 90 度呢

链接：https://developer.apple.com/documentation/appkit/nsview?language=objc

官方文档
官方提供了以上方法

如何使用呢：

let cent_x = imageView.frame.origin.x + imageView.frame.size.width/2
let cent_y = imageView.frame.origin.y + imageView.frame.size.height/2
let wid = imageView.frame.size.width
let hei = imageView.frame.size.height
let newFrame = CGRect.init(x: cent_x-hei/2, y: cent_y-wid/2, width: hei, height: wid)
imageView.frame = newFrame
imageView.translateOrigin(to: NSPoint.init(x: cent_x, y: cent_y))
imageView.rotate(byDegrees: -90)
currentRotate += 1

需要注意的点：

1. imageView是一个 NSImageView，由于NSImageView集成自NSControl，NSControl集成自NSView，此例使用NSImageView没毛病
2. imageView要设置的尽可能大一些，以防旋转后图片被挤压
3. currentRotate是用来记录旋转角度的
4. 由于旋转的是整个控件，所以当用这个控件加载其他的图片的时候，要旋转回去
5. 需要重新设置控件的 frame，否则样式会异常，猜测是translateOrigin方法中传的点并不贴切导致的

核心代码展示：

    //用于记录旋转角度
    var currentRotate:Int = 0{
        didSet{
            if currentRotate == -4 || currentRotate == 4 {
                currentRotate = 0
            }
            print("currentRotete",currentRotate)
        }
    }

    //顺时针旋转 90 度
    @IBAction func turnRight90(_ sender: NSButton?) {
        let cent_x = imageView.frame.origin.x + imageView.frame.size.width/2
        let cent_y = imageView.frame.origin.y + imageView.frame.size.height/2
        let wid = imageView.frame.size.width
        let hei = imageView.frame.size.height
        let newFrame = CGRect.init(x: cent_x-hei/2, y: cent_y-wid/2, width: hei, height: wid)
        imageView.frame = newFrame
        imageView.translateOrigin(to: NSPoint.init(x: cent_x, y: cent_y))
        imageView.rotate(byDegrees: -90)
        currentRotate += 1
    }

    //逆时针旋转 90 度
    @IBAction func turnLeft90(_ sender: NSButton?) {
        
        let cent_x = imageView.frame.origin.x + imageView.frame.size.width/2
        let cent_y = imageView.frame.origin.y + imageView.frame.size.height/2
        let wid = imageView.frame.size.width
        let hei = imageView.frame.size.height
        let newFrame = CGRect.init(x: cent_x-hei/2, y: cent_y-wid/2, width: hei, height: wid)
        imageView.frame = newFrame
        imageView.translateOrigin(to: NSPoint.init(x: cent_x, y: cent_y))
        imageView.rotate(byDegrees: 90)
        currentRotate -= 1

    }

恢复旋转角度的代码：

        while currentRotate != 0 {
            if currentRotate > 0 {
                turnLeft90(nil)
            }else{
                turnRight90(nil)
            }
        }