如何在接近尾声时更改 UIProgressView 色调颜色

Question

所以，我在一个基本的费用跟踪应用程序中有一个 UIProgressView，我想在它到达终点时逐渐从绿色变为红色来更改它的进度色调。我真的不知道该怎么做（我刚开始 swift 和 Xcode）。

大致应该是这样工作的：我的进度是用这条线计算的：
let progress = Float(UserDefaults.standard.double(forKey: "spentThisMonth") / UserDefaults.standard.double(forKey: "monthlyExpenseLimit"))
progressView.progress = progress

这里我将用户本月花费的金额除以限额以获得进度。当用户接近限制时，进度色调变为红色，表示用户应降低支出。

类似，但我认为它是 Objective-C，而我使用 Swift 5. 有什么办法可以做到这一点，即可能吗？我也是 Stack Overflow 的新手，所以如果我做错了什么，我提前道歉。

Answer 1

当然可以使用 Swift 来完成。这里的代码来自 Swift:

中的答案

func changeSendProg(progress: CGFloat) {
    let redBlueValue: CGFloat = (255 - (255 * progress)) / 255
    let colorProg = UIColor(red: redBlueValue, green: redBlueValue, blue: 1.0, alpha: 1.0)

    sendProgress.setTintColor(colorProg)
    sendProgress.setProgress(progress)
}

Answer 2

您可以使用您已经计算出的 progress 值轻松设置绿色/红色色调：

    let progress = Float(UserDefaults.standard.double(forKey: "spentThisMonth") / UserDefaults.standard.double(forKey: "monthlyExpenseLimit"))

    // progress is now a value between 0.0 and 1.0
    progressView.progress = progress

    let red = CGFloat(progress)
    let green = CGFloat(1.0 - progress)
    progressView.progressTintColor = UIColor(red: red, green: green, blue: 0.0, alpha: 1.0)

这是一个工作示例 - 每次点击屏幕时，进度都会递增，直到达到 100%，届时它会递减回零：

class ProgressTintViewController: UIViewController {
    
    let progressView = UIProgressView()
    let statsLabel = UILabel()
    
    var spentThisMonth: Float = 0
    var monthlyExpenseLimit: Float = 100
    var isAdding: Bool = true
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        progressView.translatesAutoresizingMaskIntoConstraints = false
        statsLabel.translatesAutoresizingMaskIntoConstraints = false
        
        view.addSubview(progressView)
        view.addSubview(statsLabel)
        
        let g = view.safeAreaLayoutGuide
        
        NSLayoutConstraint.activate([

            progressView.topAnchor.constraint(equalTo: g.topAnchor, constant: 80.0),
            progressView.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            progressView.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),

            statsLabel.topAnchor.constraint(equalTo: progressView.bottomAnchor, constant: 20.0),
            statsLabel.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 20.0),
            statsLabel.trailingAnchor.constraint(equalTo: g.trailingAnchor, constant: -20.0),

        ])
        
        statsLabel.numberOfLines = 0
        
        let t = UITapGestureRecognizer(target: self, action: #selector(self.tapped))
        view.addGestureRecognizer(t)
        
        updateProgress()
    }

    @objc func tapped() -> Void {
        
        if isAdding {
            spentThisMonth += 10
        } else {
            spentThisMonth -= 10
        }

        updateProgress()
        
        if spentThisMonth >= monthlyExpenseLimit {
            spentThisMonth = monthlyExpenseLimit
            isAdding = false
        }
        
        if spentThisMonth <= 0 {
            spentThisMonth = 0
            isAdding = true
        }

    }
    
    func updateProgress() -> Void {
        
        //let progress = Float(UserDefaults.standard.double(forKey: "spentThisMonth") / UserDefaults.standard.double(forKey: "monthlyExpenseLimit"))
        // progress is now a value between 0.0 and 1.0
        
        let progress = spentThisMonth / monthlyExpenseLimit
        progressView.progress = progress

        let red = CGFloat(progress)
        let green = CGFloat(1.0 - progress)
        progressView.progressTintColor = UIColor(red: red, green: green, blue: 0.0, alpha: 1.0)

        var str = ""
        str += "Tap to change progress"
        str += "\n\n"
        str += "Spent This Month: \(spentThisMonth)"
        str += "\n"
        str += "Monthly Limit: \(monthlyExpenseLimit)"
        str += "\n"
        str += "Percent: \(progress)"
        
        statsLabel.text = str
        
    }
    
}

如何在接近尾声时更改 UIProgressView 色调颜色

How to change UIProgressView tint colour as it approaches the end

xcode

uiprogressview

ios

swift