如何根据另一个组件中的选定值更改UIPickerView组件中的行数

Question

Google日历应用具有一项功能，您可以自定义何时在事件发生之前发送通知。如果您不熟悉它，它看起来像这样：

Google Calendar Custom Notification

本质上是一个选择器视图，包含两个部分，第一个显示供用户选择的数字，第二个显示时间单位（“分钟”，“小时”，“天”，“周”）。当用户选择时间单位时，数字会更改。例如，如果用户选择“分钟”作为单位，则第一个部分将显示1到60。如果他们选择“小时”，则第一个部分将显示1到24。选择“天”将显示1到28，并且“周”将显示1到4。

我想开发类似的功能，但是当我运行代码时，出现错误“索引超出范围”。该代码块的最后一个函数中发生错误。在调试部分，“行”的值为0。我认为该错误与数组大小的差异有关，但我不确定。感谢所有帮助！

import UIKit
class AlarmSet
{
    func timeIntervals() -> [String]
    {
        return ["minutes", "hours", "days", "weeks"]
    }

    func timeValues(time: String) -> [Int]
    {
        switch time
        {
            case "minutes":
                return Array(1...60)
            case "hours":
                return Array(1...24)
            case "days":
                return Array(1...28)
            case "weeks":
                return [1, 2, 3, 4]
            default:
                return [0]
        }
    }
}

class ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate 
{

    @IBOutlet weak var addAlarm: UIButton!
    @IBOutlet weak var alarmView: UIPickerView!

    //The first component of the picker displays numbers
    var picker1Options:[Int] = []
    //The second picker displays units of time (minutes, hours, etc.)
    var picker2Options:[String] = []

    override func viewDidLoad()
    {
        super.viewDidLoad()
        alarmView.delegate = self
        alarmView.dataSource = self
        alarmView.delegate?.pickerView?(alarmView, didSelectRow: 0, inComponent: 0)
        alarmView.delegate?.pickerView?(alarmView, didSelectRow: 0, inComponent: 1)

        alarmView.isHidden = true
        let alarm = AlarmSet();

        picker2Options = alarm.timeIntervals()
        let firstValue = picker2Options[0]
        picker1Options = alarm.timeValues(time: firstValue)

        // Do any additional setup after loading the view.
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int
    {
        return 2
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int
    {
        if component == 1
        {
            return picker2Options.count
        }
        else
        {
            return picker1Options.count
        }
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String?
    {
        if component == 0 
        {
            return "\(picker1Options[row])"
        } 
        else 
        {
        return "\(picker2Options[row])"
        }
    }

    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int)
    {
        if component == 1
        {
            let alarm = AlarmSet();
            //Out of range error is on this next line
            let currentValue = picker2Options[row]
            picker1Options = alarm.timeValues(time: currentValue)
            pickerView.reloadAllComponents()
        }
    }
}

Answer 1

您正在打电话

alarmView.delegate?.pickerView?(alarmView, didSelectRow: 0, inComponent: 0

在设置picker2Options变量之前，在viewDidLoad中，因此当picker2Options为空时，它试图访问picker2Options [0]。在调用委托方法之前设置数组