ios - 限制和缩放 UITextField 中文本的大小

Question

我有一个带有两个 CAShapeLayers 的 UITextField。我希望我的文本始终居中并限制(大小)到内部白色圆圈。

如何限制白色圆圈内文本的大小(最好使用填充)，同时又使文本始终填充该空间？第二部分问题与缩放因子有关，如果有更多文本，该缩放因子会将文本字体大小设置得更小。

这是我的 MWE:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        self.view.backgroundColor = .darkGray

        let size:CGFloat = 300.0
        let centerPoint:CGFloat = 200.0

        let valueLabel = UITextField()
        valueLabel.isUserInteractionEnabled = false
        valueLabel.contentVerticalAlignment = .center
        valueLabel.textAlignment = .center
        valueLabel.text = "300"
        valueLabel.textColor = .black

        valueLabel.font = UIFont.init(name: "HelveticaNeue-Medium", size: 100)
        valueLabel.bounds = CGRect(x:0.0, y:0.0, width:size, height:size)
        valueLabel.center = CGPoint(x:centerPoint, y:centerPoint)

        let redCircle:CAShapeLayer = CAShapeLayer()
        redCircle.path = UIBezierPath(ovalIn: valueLabel.bounds).cgPath
        redCircle.fillColor = UIColor.red.cgColor
        redCircle.strokeColor = UIColor.white.cgColor
        redCircle.lineWidth = 10

        valueLabel.layer.addSublayer(redCircle)

        let whiteCircle:CAShapeLayer = CAShapeLayer()
        let tmpRect = CGRect(x:valueLabel.bounds.origin.x,y:valueLabel.bounds.origin.x,width:valueLabel.bounds.width-80.0,height:valueLabel.bounds.height-80.0)
        whiteCircle.path = UIBezierPath(ovalIn: tmpRect).cgPath
        whiteCircle.fillColor = UIColor.white.cgColor
        whiteCircle.strokeColor = UIColor.white.cgColor
        whiteCircle.lineWidth = 10
        let posX = valueLabel.bounds.midX - (size-80.0)/2.0
        let posY = valueLabel.bounds.midY - (size-80.0)/2.0
        whiteCircle.position = CGPoint(x:posX, y:posY)
        valueLabel.layer.addSublayer(whiteCircle)

        self.view.addSubview(valueLabel)
    }
}

Answer 1

为此，我建议使用 UITextView，它通过 NSTextContainer 对此提供 native 支持。 docs

textView.textContainer.exclusionPaths = [..] // array of UIBezierPaths