如何将UISlider的值从SettingsVC传递到ViewController页面？

问题根源 #

你在ViewController的controll()方法里直接创建了SettingsVC()的新实例，这个实例和你之前弹出的设置页面实例完全无关，所以获取到的是滑块的默认值，不是用户调整后的数值。同时你没有在两个页面之间建立值传递的通道。

方案一：使用闭包（推荐，实现简单） #

1. 修改SettingsVC，添加闭包属性

在SettingsVC里定义一个闭包，用于用户点击Done时传递滑块值：

import UIKit

class SettingsVC: UIViewController {
 
    //MARK: - Sliders
    var focusTimeSlider = UISlider()
    let shortBreakTimeSlider = UISlider()
    let longBreakTimeSlider = UISlider()
    
    // 添加闭包属性，用于传递设置值
    var onSettingsSaved: ((Int, Int, Int) -> Void)?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground
        title = "Settings"
        addCloseButton() // 调用添加按钮方法，确保Done按钮显示
    }
    
    //MARK: - Done Button
    func addCloseButton(){
        let button = UIBarButtonItem(title: "Done", style: .done, target: self, action: #selector(onClose))
        navigationItem.rightBarButtonItem = button
    }
    
    @objc func onClose(){
        let focusTime = Int(focusTimeSlider.value)
        let shortBreakTime = Int(shortBreakTimeSlider.value)
        let longBreakTime = Int(longBreakTimeSlider.value)
        
        // 调用闭包传递值
        onSettingsSaved?(focusTime, shortBreakTime, longBreakTime)
        
        self.dismiss(animated: true, completion: nil)
        
        print("Focus Time       : \(focusTime)")
        print("Short Break Time : \(shortBreakTime)")
        print("Long Break Time  : \(longBreakTime)")
    }
    
    // 滑块相关代码保持不变
    //MARK: - Slider Actions
    func layoutFocusTimeSlider(){
        focusTimeSlider.addTarget(self, action: #selector(focusSliderValueChanged(sender:)), for: .valueChanged)
    }
    
    @objc func focusSliderValueChanged(sender: UISlider){
        focusTimeSliderValueLabel.text = String(Int(focusTimeSlider.value))
    }
    
    func layoutShortBreakTimeSlider(){
        shortBreakTimeSlider.addTarget(self, action: #selector(shortSliderValueChanged), for: .valueChanged)
    }
    
    @objc func shortSliderValueChanged(){
        shortBreakTimeSliderValueLabel.text = String(Int(shortBreakTimeSlider.value))
    }

    func layoutLongBreakTimeSlider(){
        longBreakTimeSlider.addTarget(self, action: #selector(longSliderValueChanged), for: .valueChanged)
    }

    @objc func longSliderValueChanged(){
        longBreakTimeSliderValueLabel.text = String(Int(longBreakTimeSlider.value))
    }
}

2. 修改ViewController，设置闭包并更新UI

弹出SettingsVC时设置闭包，接收传递回来的值并更新页面显示：

import UIKit

class ViewController: UIViewController {
  
    let actionButton = SFActionButton()
    var minutesLabel = SFTimeLabel(text: "25")
    let secondsLabel = SFTimeLabel(text: "00")
    // 可以新增属性保存设置值
    private var savedFocusTime = 25
    
    override func viewDidLoad() {
        super.viewDidLoad()
        view.backgroundColor = .systemBackground
        // 读取本地保存的设置，初始化页面
        let savedTime = UserDefaults.standard.integer(forKey: "FocusTime")
        if savedTime != 0 {
            savedFocusTime = savedTime
            minutesLabel.text = String(savedFocusTime)
        }
    }
    
    @objc func controll(){
        print("Saved Focus Time : \(savedFocusTime)")
    }
    
    @objc func settingsAction(){
        let rootVC = SettingsVC()
        // 设置闭包接收值
        rootVC.onSettingsSaved = { [weak self] focusTime, shortBreak, longBreak in
            guard let self = self else { return }
            // 更新主页面显示
            self.savedFocusTime = focusTime
            self.minutesLabel.text = String(focusTime)
            // 保存到本地，下次启动保留设置
            UserDefaults.standard.set(focusTime, forKey: "FocusTime")
            UserDefaults.standard.set(shortBreak, forKey: "ShortBreakTime")
            UserDefaults.standard.set(longBreak, forKey: "LongBreakTime")
        }
        let navVC = UINavigationController(rootViewController: rootVC)
        navVC.modalPresentationStyle = .fullScreen
        self.present(navVC, animated: true, completion: nil)
    }
    
}

额外提示 #

• 确保SettingsVC里的addCloseButton()在viewDidLoad中被调用，否则Done按钮不会显示。
• 使用UserDefaults保存设置值，可以让用户调整的时长在应用重启后依然保留。

内容的提问来源于stack exchange，提问作者user15200527