旋转图像视图，该图像视图应位于底部固定点的圆弧内

Question

我正在创建一个速度计。我的图像底部必须位于圆弧的中心点，我需要使用固定的中心点旋转图像。我不知道该怎么做。

    private func drawHand(center: CGPoint) {
        let handImage = UIImage(named: "hand")
        handImageView = UIImageView(image: handImage)

        handImageView.translatesAutoresizingMaskIntoConstraints = false
        handImageView.bounds = CGRect(x: center.x, y: center.y, width: 100, height: bounds.height / 3)
        handImageView.layer.anchorPoint = CGPoint(x: 0, y: 0.5)

        handImageView.center = CGPoint(x: bounds.midX, y: bounds.midY)
        addSubview(handImageView)
    }

这是我的代码，我试图将图像居中放置在圆弧内，但我的图像却在左上角。

我尝试使用旋转

            handImageView.transform = CGAffineTransform(rotationAngle: deg2rad(handRotation))

但没有任何工作正常。请帮助我将我的图像设置在圆弧中心然后旋转它。

Answer 1

这一行：

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

您已将锚点设置为左边缘和垂直中心

改成这样：

// set the anchorPoint to Horizontal Center / Bottom Edge
handImageView.layer.anchorPoint = CGPoint(x: 0.5, y: 1.0)

看看你是否得到了你想要的旋转。

这是一个完整的示例...箭头从零度开始（向上）——每次点击都会增加 10 度的旋转：

extension Double {
    var degreesToRadians: Self { self * .pi / 180 }
    var radiansToDegrees: Self { self * 180 / .pi }
}

class ViewController: UIViewController {

    var handImageView: UIImageView!
    
    var handRotation: Double = 0
    
    override func viewDidLoad() {
        super.viewDidLoad()

        let handImage = UIImage(systemName: "arrow.up")
        handImageView = UIImageView(image: handImage)
        
        // so we can see the image view frame
        handImageView.backgroundColor = .systemYellow
        
        view.addSubview(handImageView)
        
        // set imageView frame to 80 x 160
        handImageView.frame = CGRect(origin: .zero, size: CGSize(width: 80, height: 160))
        
        // set the anchorPoint to Horizontal Center / Bottom Edge
        handImageView.layer.anchorPoint = CGPoint(x: 0.5, y: 1.0)
        
        // set image view's Anchor Point to the center of the view
        handImageView.center = view.center
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        // increment rotation by 10-degrees with each touch
        //  Zero-degrees is pointing UP (12 o'clock)
        handRotation += 10
        handImageView.transform = CGAffineTransform(rotationAngle: CGFloat(handRotation.degreesToRadians))
        print("rotation:", handRotation)
    }

}

旋转图像视图，该图像视图应位于底部固定点的圆弧内

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