UIPIckerViews 在一个 UIView 中协同工作

Question

查看了其他类似的问题，但没有找到答案。整理了我遇到的一些问题，但仍然存在第一个 pickerView 中的数据确定第二个 pickerView 中有哪些选择的问题（应用程序的这一部分是单位转换器）。

我了解出了什么问题，但不知道如何解决问题。通过打印语句我可以看到，当我更改第一个pickerView 时，保存第二个pickerView 中的行数的值发生了变化。但是第二个 pickerView 标题不会改变，因此当我转到高于新数组中索引号的项目时，应用程序会崩溃。错误索引超出范围证实了这一点。

我已经包含了代码和 pickerViews 外观的快照（没有格式化或使其漂亮 - 喜欢首先获得功能）。

感谢您的帮助。

import UIKit

导入基础

类 ViewController: UIViewController, UIPickerViewDataSource, UIPickerViewDelegate {

var conversionTypes = ["length", "mass", "area", "volume", "rate", "temp", "pressure"]
var conversionItems = [["metres", "feet", "yard", "inch", "cm"], ["kg", "lbs", "tonne", "ounces"], ["ft2", "m2", "in2"], ["US Gall", "UK Gall", "Bbls", "ft3", "m3"], ["bbl/min", "scf/min", "scf/hr"], ["degC", "degF", "Kelvin"], ["bar", "psi"]]
var littlePickerType = 0
var wheelOne = 0
var wheelTwo = 0



@IBOutlet weak var numberToConvert: UITextField!
@IBOutlet weak var answerLabel: UILabel!


@IBOutlet weak var littlePicker: UIPickerView!
@IBOutlet weak var bigPicker: UIPickerView!


override func viewDidLoad() {
    super.viewDidLoad()
    // Do any additional setup after loading the view.
    littlePicker.delegate = self
    littlePicker.dataSource = self
    bigPicker.delegate = self
    bigPicker.dataSource = self

    let tap = UITapGestureRecognizer(target: self.view, action: #selector(UIView.endEditing))
    view.addGestureRecognizer(tap)
}


func numberOfComponents(in pickerView: UIPickerView) -> Int {
    if pickerView == littlePicker {
        return 1
    } else if pickerView == bigPicker {
        return 2
    }

    return 1
}


func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
    if pickerView == littlePicker {
        return conversionTypes.count
    } else if pickerView == bigPicker {
        return conversionItems[littlePickerType].count
    }

    return 1
}

func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {

    if pickerView == littlePicker {
        return conversionTypes[row]
    } else if pickerView == bigPicker {
        return conversionItems[littlePickerType][row]
    }
    return ""
}

func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {

    if pickerView == littlePicker {
        littlePickerType = row
    } else if pickerView == bigPicker {
        if component == 0 {
            wheelOne = row
        } else if component == 1 {
            wheelTwo = row
        }
    }

    print ("Conversion Type \(littlePickerType) WheelOne \(wheelOne) WheelTwo \(wheelTwo) count \(conversionItems[littlePickerType].count)")


}

}

Answer 1

每当littlePickerType 更改时，您都应该在您的大选择器上调用reloadAllComponents。这会导致为大选择器再次调用所有选择器视图数据源方法（尤其是 titleForRow）。

var littlePickerType = 0 {
    didSet {
        bigPicker.reloadAllComponents()
    }
}