带有属性字符串的 UIPickerView

Question

根据 Apple 的文档，有一个名为 pickerView(_:attributedTitleForRow:forComponent:) 的 UIPickerView 委托函数。但是，我试图让它工作，但我似乎在这里做错了什么。我希望有人能帮助我。

为了简单起见，我有一个简单的程序，它在选择器视图的两个组件中显示两个数组的内容。该程序只是一个视图控制器和一个选择器视图。代码呈现给她：

import UIKit

class ViewController: UIViewController, UIPickerViewDelegate, UIPickerViewDataSource {

var familyNames = [String]()
var fontName = ""
let firstArray = Array(0...99)
let secondArray = Array(0...99)
let fontCount = 0

@IBOutlet weak var samplePickerView: UIPickerView!
@IBOutlet weak var fontLabel: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    familyNames = UIFont.familyNames.sorted()
    let fontNames = UIFont.fontNames(forFamilyName: familyNames[17])
    fontName = fontNames.first!

    samplePickerView.delegate = self
    samplePickerView.dataSource = self
}

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

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {

    if component == 0 {
        return firstArray.count
    } else {
        return secondArray.count
    }
}

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

    var rowTitle = ""
    let font = UIFont(name: fontName, size: 18.0)
    let stringDictionary = [NSAttributedString.Key.font: font]

    switch component {
    case 0:
        rowTitle = String(format: "%03d", firstArray[row])
    case 1:
        rowTitle = String(format: "%03d", secondArray[row])
    default:
        break
    }

    let returnString = NSAttributedString(string: rowTitle, attributes: stringDictionary as [NSAttributedString.Key : Any])
    print(returnString)
    return returnString
}

}

选择器视图现在应显示 Bradley Hand 中的标题，因此很容易发现有效的标题。不幸的是，选择器视图没有在属性字符串中显示标题。委托方法返回的字符串是一个属性字符串，所以它应该可以工作。图片显示情况并非如此。我究竟做错了什么？

Answer 1

问题来了

familyNames = UIFont.familyNames.sorted()

你得到了 字体家族 的名称，但是 UIFont 初始化程序将 字体名称 作为参数，而不是它的姓氏。来自 Apple Documentation:

familyNames

Font family names correspond to the base name of a font, such as Times New Roman. You can pass the returned strings to the fontNames(forFamilyName:) method to retrieve a list of font names available for that family. You can then use the corresponding font name to retrieve an actual font object.

因此，如果您想获取给定姓氏的字体名称，请使用以下方法。然后你可以使用它们来创建字体。

UIFont.fontNames(forFamilyName: String)

此外，不要通过像 familyNames[17] 这样的魔术索引号来访问您的字体系列名称，这是一种糟糕的方法。您可能会越界，这会使您的应用程序崩溃。

我会将我的字体名称存储在一个常量中，例如

let pickerFontName = "MyAwesomeFont"

// later in your program
let font = UIFont(name: pickerFontName, size: 18.0)

Answer 2

在没有找到解决方案后，我在 Apple 请求了 DTS 以了解我做错了什么。显然，我没有做错任何事，但是 "pickerView(_ pickerView: UIPickerView, attributedTitleForRow row: Int, forComponent component: Int) -> NSAttributedString?" 方法不允许您对属性字符串进行太多操作。 Apple 的回答是："UIPickerView’s attributedTitleForRow delegate won’t change the font attribute, but will work for other attributes like font color."

幸运的是，由于我想更改字体大小和字体，所以有一种方法可以在 UIPickerView 中获取不同的字体和字体大小。苹果提供的解决方案："If you want to use all the font attributes available in NSAttributedString, use viewForRow and return a UILabel as an alternative."

代码现在看起来像这样： var familyNames = 字符串 var 字体名称 = "" 让 firstArray = Array(0...99) 让 secondArray = Array(0...99) 让 fontCount = 0

@IBOutlet weak var samplePickerView: UIPickerView!
@IBOutlet weak var fontLabel: UILabel!

override func viewDidLoad() {
    super.viewDidLoad()

    familyNames = UIFont.familyNames.sorted()
    let fontNames = UIFont.fontNames(forFamilyName: familyNames[17])
    fontName = fontNames.first!

    samplePickerView.delegate = self
    samplePickerView.dataSource = self
}

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

func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {

    if component == 0 {
        return firstArray.count
    } else {
        return secondArray.count
    }
}

func pickerView(_ pickerView: UIPickerView, viewForRow row: Int, forComponent component: Int, reusing view: UIView?) -> UIView {

    var rowTitle = ""
    let pickerLabel = UILabel()

    pickerLabel.textColor = UIColor.blue

    switch component {
        case 0:
            rowTitle = String(format: "%03d", firstArray[row])
        case 1:
            rowTitle = String(format: "%03d", secondArray[row])
        default:
            break
    }

    pickerLabel.text = rowTitle
    pickerLabel.font = UIFont(name: fontName, size: 24.0)
    pickerLabel.textAlignment = .center

    return pickerLabel
}

结果如下所示：这是我想对选择器视图中的文本进行的操作。

带有属性字符串的 UIPickerView

UIPickerView with attributes string

ios

swift

uipickerview