ios - UIProgressBar:如何根据背景颜色更改UILabel颜色

Question

我是 iOS 编程新手。我想创建一个带有 UIlabel 的进度条，它还会根据背景颜色更改文本颜色，如下所示:

请不要将该问题标记为重复。因为我找到的解决方案是在 Obj C 或一些 Pod 中。但我想要 Swift 中的解决方案，因为我对 Obj-C 没有任何了解。

谢谢!

Answer 1

如果你想用 swift 得到答案，这里是来自 post 的代码(从 objc 更改为 swift) ，这应该正是您所需要的:

这太快了4

class MyProgressView: UIView {

    var progress: CGFloat = 0 {
        didSet {
            setNeedsDisplay()
        }
    }

    override func draw(_ rect: CGRect) {
        let context = UIGraphicsGetCurrentContext()

        // Set up environment.
        let size = bounds.size
        let backgroundColor = UIColor(red: 108/255, green: 200/255, blue: 226/255, alpha: 1)
        let foregroundColor = UIColor.white
        let font = UIFont.boldSystemFont(ofSize: 42)

        // Prepare progress as a string.
        let progress = NSString(format: "%d%%", Int(round(self.progress * 100))) // this cannot be a String because there are many subsequent calls to NSString-only methods such as `size` and `draw`
        var attributes: [NSAttributedString.Key: Any] = [.font: font]
        let textSize = progress.size(withAttributes: attributes)
        let progressX = ceil(self.progress * size.width)
        let textPoint = CGPoint(x: ceil((size.width - textSize.width) / 2), y: ceil((size.height - textSize.height) / 2))

        // Draw background + foreground text
        backgroundColor.setFill()
        context?.fill(bounds)
        attributes[.foregroundColor] = foregroundColor
        progress.draw(at: textPoint, withAttributes: attributes)

        // Clip the drawing that follows to the remaining progress's frame
        context?.saveGState()
        let remainingProgressRect = CGRect(x: progressX, y: 0, width: size.width - progressX, height: size.height)
        context?.addRect(remainingProgressRect)
        context?.clip()

        // Draw again with inverted colors
        foregroundColor.setFill()
        context?.fill(bounds)
        attributes[.foregroundColor] = backgroundColor
        progress.draw(at: textPoint, withAttributes: attributes)

        context?.restoreGState()
    }
}

在 Playground 进行测试