更改 swift 中多个 colors 的 UISlider 轨道颜色？

Question

当 slider 移动时，我可以使用我获得的值 (sender.value) 来改变颜色吗？ 随着 slider 的移动，我正在尝试将颜色从绿色变为黄色再变为红色。 请帮忙swift谢谢！

let brokeSlider = UISlider(frame:CGRectMake(5, 440, 355, 20))
            brokeSlider.minimumValue = 0
            brokeSlider.maximumValue = 1
            brokeSlider.continuous = true
            brokeSlider.tintColor = UIColor.blackColor()
            brokeSlider.value = 0
            brokeSlider.addTarget(self, action: #selector(AnnotationPhotoWidget.sliderValueDidChange(_:)), forControlEvents: .ValueChanged)
            self.view.addSubview(brokeSlider)

    func sliderValueDidChange(sender:UISlider) {
            print("value--\(sender.value)")
    }

Answer 1

尝试以下代码：

func sliderValueDidChange(sender:UISlider) {
     print("value--\(sender.value)")
     if sender.value <= 0.3 {
        brokeSlider.minimumTrackTintColor = UIColor.greenColor()
     } else if sender.value > 0.3 && sender.value <= 0.6 {
           brokeSlider.minimumTrackTintColor = UIColor.yellowColor()
     } else {
          brokeSlider.minimumTrackTintColor = UIColor.redColor()
     }
}

Answer 2

@ashimVerma 的解决方案效果很好。 要提高一个档次并获得平滑的颜色过渡，请试一试：

@objc func sliderValueDidChange(sender: UISlider) {
    let saturation = 0.9 // 0...1
    let lightness = 0.46 // 0...1

    let sliderPercentage = sender.value / sender.maximumValue
    let invertedPercentage = 1 - sliderPercentage
    let hue = CGFloat(invertedPercentage * 120 / 360)

    let brightness = lightness + saturation * min(lightness, 1 - lightness)

    var adjustedSaturation: CGFloat = 0.0
    if brightness > 0 {
        adjustedSaturation = 2 * (1 - lightness / brightness)
    }

    let trackColor = UIColor(hue: hue, saturation: adjustedSaturation, brightness: brightness, alpha: 1)
    brokeSlider.minimumTrackTintColor = trackColor
}

这是通过利用饱和度和亮度恒定的 HSL 色彩空间来实现的。 所以我们只需要根据总色调范围的一部分来改变色调（从绿色到红色）。 然后我们将这些值转换为使用 UIColor 的 HSB 初始值设定项。

参考： https://en.wikipedia.org/wiki/Hue

更简单：

如果您不需要在 HSL 色彩空间中工作，可以通过直接设置饱和度和亮度值来进一步简化。

@objc func sliderValueDidChange(sender: UISlider) {
    let sliderPercentage = sender.value / sender.maximumValue
    let invertedPercentage = 1 - sliderPercentage
    let hue = CGFloat(invertedPercentage * 120 / 360)

    let trackColor = UIColor(hue: hue, saturation: 0.95, brightness: 0.87, alpha: 1)
    brokeSlider.minimumTrackTintColor = trackColor
}

Answer 3

尝试这个：

import Foundation
import UIKit

class AnnotationPhotoWidget: UIViewController  {
    let brokeSlider = UISlider(frame:CGRectMake(5, 440, 355, 20))

    override func viewDidLoad() {
        brokeSlider.minimumValue = 0
        brokeSlider.maximumValue = 1
        brokeSlider.continuous = true
        brokeSlider.tintColor = UIColor.blackColor()
        brokeSlider.value = 0
        brokeSlider.addTarget(self, action: #selector(AnnotationPhotoWidget.sliderValueDidChange(_:)),forControlEvents: .
            ValueChanged)
        self.view.addSubview(brokeSlider)
    }

    func sliderValueDidChange(sender: UISlider) {
        if sender.value <= 0.3 {
            brokeSlider.minimumTrackTintColor = UIColor.greenColor()
        } else if sender.value > 0.3 && sender.value <= 0.6 {
            brokeSlider.minimumTrackTintColor = UIColor.yellowColor()
        } else {
            brokeSlider.minimumTrackTintColor = UIColor.redColor()
        }
    }
}