UIPickerView 冻结UI

Question

在我的应用程序中，我有一个包含两个组件的 ViewController：一个 UILabel，用户可以像时钟一样使用；UIPickerView 允许用户 select 一个项目。

这里有代码：

class MyView: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource{

@IBOutlet weak var lblClock: UILabel!
@IBOutlet weak var pickerAttendance: UIPickerView!
var timer : Timer!
var dateTime: Date!
var pickerData: [String] = ["a","b","c"]

   override func viewDidLoad() {
        super.viewDidLoad()

        dateTime = Date()
        timer = Timer.scheduledTimer(timeInterval: TimeInterval(1), target: self, selector: #selector(updateDate), userInfo: nil, repeats: true)
        timer.fire()

        pickerAttendance.delegate = self
        pickerAttendance.dataSource = self
   }

    @objc func updateDate(){
        dateTime = NSCalendar.current.date(byAdding: Calendar.Component.second, value: 1, to: self.dateTime)
        let s = DateFormatter.localizedString(from: self.dateTime, dateStyle: DateFormatter.Style.none, timeStyle: DateFormatter.Style.medium)
        DispatchQueue.main.async {
            self.lblClock.text = s
        }
    }

   func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
   }

   func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return pickerData.count
   }

   func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return pickerData[row]
   }
}

我实例化了一个具有实际值的日期和一个计时器，该函数每隔一秒更新一次标签的值。我解释我的问题：当我滚动 pickerview 时，带有计时器的标签不会更新，但是当我释放滚动时，标签会重新开始更新。

滚动条冻结 ui。

我已经尝试更新主线程中的标签，但问题仍然存在。我希望当我滚动选择器视图时，标签将继续更新。

Answer 1

将您的计时器置于运行循环中：

override func viewDidLoad() {
    super.viewDidLoad()

    dateTime = Date()
    timer = Timer.scheduledTimer(timeInterval: TimeInterval(1), target: self, selector: #selector(updateDate), userInfo: nil, repeats: true)

    RunLoop.main.add(timer, forMode: RunLoop.Mode.common)

    timer.fire()

    pickerAttendance.delegate = self
    pickerAttendance.dataSource = self
}

UIPickerView 冻结UI

UIPickerView freeze UI

ios

swift

uipickerview