Swift + Autolayout:旋转 UILabel，将其放在 UIView 旁边 [英] Swift + Autolayout: Rotate UILabel, keep it next to UIView

问题描述

我想要一个 UILabel 附加到另一个 UIView，目前使用 AutoLayout 布局.

I would like to have a UILabel attached to another UIView, currently layed out with AutoLayout.

我想实现的目标如下:

但是如果我只旋转视图，它会围绕中心点旋转，如果我改变锚点，上面的视图就会移动.如何首先使用自动布局布局两个视图，然后进行旋转?

But if I only rotate the view, it's rotated around the center point, and if I change the anchor point, the upper view moves. How do I have to layout the two views with autolayout first and then make the rotation?

目前，自动布局执行以下操作:

Currently, autolayout does the following:

使用以下代码:

    label.layer.anchorPoint = CGPoint(x: 0, y: 0)
    label.layer.transform = CATransform3DMakeRotation(CGFloat(-45 / 180.0 * CGFloat(M_PI)), 0, 0, 1)

我确实得到了类似的东西

I do get something like

推荐答案

不要改变锚点，因为那样会搞乱自动布局.

Don't change the anchor point, because that will mess up autolayout.

相反，在变换中补偿锚点的位置:

Instead, compensate for the anchor point's position in your transform:

class ViewController: UIViewController {

    @IBOutlet var label: UILabel!
    @IBOutlet var slider: UISlider!

    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        updateTransform()
    }

    @IBAction func sliderValueChanged(_ sender: Any) {
        updateTransform()
    }

    private func updateTransform() {
        var transform = CGAffineTransform.identity
        let labelSize = label.bounds.size
        transform = transform.translatedBy(x: -labelSize.width / 2, y: labelSize.height / 2)
        transform = transform.rotated(by: -CGFloat(slider.value) * CGFloat.pi / 2)
        transform = transform.translatedBy(x: labelSize.width / 2, y: -labelSize.height / 2)
        label.transform = transform
    }

}

结果:

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