ios - 在 View Controller 之外选择 UISegmentedController 段

Question

我有一个带有分层容器 View 的 ViewController，以及这个 SegmentedController 代码:

@IBOutlet weak var dayPicker: UISegmentedControl!

@IBAction func dayPickerControl(sender: UISegmentedControl) {

    switch dayPicker.selectedSegmentIndex {
    case 0:
        monContainer.hidden = false
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 1:
        monContainer.hidden = true
        tuesContainer.hidden = false
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 2:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = false
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 3:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = false
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = true
    case 4:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = false
        satContainer.hidden = true
        sunContainer.hidden = true
    case 5:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = false
        sunContainer.hidden = true
    case 6:
        monContainer.hidden = true
        tuesContainer.hidden = true
        wedContainer.hidden = true
        thursContainer.hidden = true
        friContainer.hidden = true
        satContainer.hidden = true
        sunContainer.hidden = false
    default:
        break;
    }

我怎样才能从另一个 View Controller 中选择某个段，以便当我返回到这个 View 时，我想要的容器是可见的，并且相应的段被选中？

Answer 1

首先，您需要在某处保存全局状态，以便您的应用程序的任何部分都可以访问。即使像共享对象(单例)或绑定(bind)到 UIApplicationDelegate 的对象这样简单的东西在这里也能正常工作。

一种选择是使用单例方法。很多人出于各种原因不喜欢使用单例，但我认为这是在这种情况下全局值的简单说明。单例的要点是在应用程序的生命周期内保留一个对象。另一种方法是将此状态绑定(bind)到 UIApplicationDelegate。

要实现单例(如果你愿意，你可以把它放在自己的文件中，我称之为 UserState 但你可以将其更改为任何你想要的):

private let _UserStateSharedInstance = UserState()

class UserState  {
    class var sharedInstance : UserState {
        return _UserStateSharedInstance
    }
    var selectedDay = 0
}

在此 View Controller 中，您可以检索选定的日期:

override func viewWillAppear(animated: Bool) {
    super.viewWillAppear(animated)
    dayPicker.selectedSegmentIndex = UserState.sharedInstance.selectedDay
}

@IBAction func dayPickerControl(sender: UISegmentedControl) {
    UserState.sharedInstance.selectedDay = sender.selectedSegmentIndex // You probably also want to set this here

    // Do your switching here
}

在您的其他 View Controller 中，您可以设置您选择的日期:

@IBAction func dayPickerControl(sender: UISegmentedControl) {
    UserState.sharedInstance.selectedDay = sender.selectedSegmentIndex
}

---

在我们讨论的时候，我可以建议一种更简单的方法来进行这种切换吗？

我们可以从将每个案例组合成一个简单的逻辑语句开始，以避免一遍又一遍地重复列表:

@IBAction func dayPickerControl(sender: UISegmentedControl) {

    let segmentIndex = sender.selectedSegmentIndex

    monContainer.hidden = (segmentIndex != 0)
    tuesContainer.hidden = (segmentIndex != 1)
    wedContainer.hidden = (segmentIndex != 2)
    thursContainer.hidden = (segmentIndex != 3)
    friContainer.hidden = (segmentIndex != 4)
    satContainer.hidden = (segmentIndex != 5)
    sunContainer.hidden = (segmentIndex != 6)
}

现在越来越明显，这只是我们要根据索引隐藏/显示的 View 数组。我们可以用循环重写它:

var viewsToHide: [UIView]?

override func viewDidLoad() {
    super.viewDidLoad()

    viewsToHide = [monContainer, tuesContainer, wedContainer, thursContainer, friContainer, satContainer, sunContainer]
}

@IBAction func dayPickerControl(sender: UISegmentedControl) {

    let segmentIndex = sender.selectedSegmentIndex

    for (index, view) in enumerate(viewsToHide ?? []) {
        view.hidden = (segmentIndex != index)
    }
}