Swift NSAttributedStringKey 没有正确应用前景色

Question

我正在尝试创建一个 meme 生成器应用程序，以更好地理解 Swift、Xdode、delegates 和 UIKit。我正在尝试使用 NSAttributedStringKey 将模因文本的颜色设置为带有黑色笔划的白色。黑色描边有效，但当用户从相机胶卷中选择图像时，未应用前景色。我已经通过 Whosebug 进行了搜索，但所有解决方案都适用于 Swift 3，而不适用于 Swift 4。我哪里错了？

我在下面包含了我的源代码。

import UIKit

class ViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate {

    @IBOutlet weak var imagePickerView: UIImageView!
    @IBOutlet weak var cameraButton: UIBarButtonItem!
    @IBOutlet weak var topText: UITextField!
    @IBOutlet weak var bottomText: UITextField!

    let memeTextAttributes:[String:Any] = [
        NSAttributedStringKey.strokeColor.rawValue: UIColor.black,
        NSAttributedStringKey.foregroundColor.rawValue: UIColor.white,
        NSAttributedStringKey.font.rawValue: UIFont(name: "HelveticaNeue-CondensedBlack", size: 40)!,
        NSAttributedStringKey.strokeWidth.rawValue: 3.0]

    override func viewDidLoad() {
        super.viewDidLoad()
        // Diable camer a button if camera ource isn't available
        cameraButton.isEnabled = UIImagePickerController.isSourceTypeAvailable(.camera)
        topText.defaultTextAttributes = memeTextAttributes
        bottomText.defaultTextAttributes = memeTextAttributes
    }

    // MARK: Delegate Methods

    func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [String : Any]) {
        if let image = info[UIImagePickerControllerOriginalImage] as? UIImage {
            imagePickerView.image = image
            self.dismiss(animated: true, completion: nil)
        }
    }

    func imagePickerControllerDidCancel(_ picker: UIImagePickerController) {
        self.dismiss(animated: true, completion: nil)
    }

    @IBAction func pickAnImageFromAlbum(_ sender: Any) {
        let pickerController = UIImagePickerController()
        pickerController.delegate = self
        pickerController.sourceType = .photoLibrary
        present(pickerController, animated: true, completion: nil)
    }

    @IBAction func pickAnImageFromCamera(_ sender: Any) {
        let imagePicker = UIImagePickerController()
        imagePicker.delegate = self
        imagePicker.sourceType = .camera
        present(imagePicker, animated: true, completion: nil)
    }
}

Answer 1

如果您还要设置 foregroundColor，请使用否定 strokeWidth。否则，只能看到笔画。

let attributes = [
        NSAttributedStringKey.strokeColor.rawValue: UIColor.black,
        NSAttributedStringKey.backgroundColor.rawValue: UIColor.red,
        NSAttributedStringKey.foregroundColor.rawValue: UIColor.white,
        NSAttributedStringKey.font.rawValue: UIFont(name: "HelveticaNeue-CondensedBlack", size: 40)!,
        NSAttributedStringKey.strokeWidth.rawValue: -4.5]

Swift 5

let attributes = [
        NSAttributedString.Key.strokeColor: UIColor.black,
        NSAttributedString.Key.backgroundColor: UIColor.red,
        NSAttributedString.Key.foregroundColor: UIColor.white,
        NSAttributedString.Key.font: UIFont(name: "HelveticaNeue-CondensedBlack", size: 40)!,
        NSAttributedString.Key.strokeWidth: -3.0]

编辑：请参阅 rmaddy 关于为什么我们需要下面这种情况下的 rawValue 的评论。

Answer 2

笔画宽度负责，负笔画值可以解决你的问题。

Swift 4.2

let attributes = [
        NSAttributedString.Key.strokeColor.rawValue: UIColor.black,
        NSAttributedString.Key.backgroundColor.rawValue: UIColor.red,
        NSAttributedString.Key.foregroundColor.rawValue: UIColor.white,
        NSAttributedString.Key.font.rawValue: UIFont(name: "HelveticaNeue-CondensedBlack", size: 40)!,
        NSAttributedString.Key.strokeWidth.rawValue: -3.0]

Swift 5

let attributes = [
        NSAttributedString.Key.strokeColor: UIColor.black,
        NSAttributedString.Key.backgroundColor: UIColor.red,
        NSAttributedString.Key.foregroundColor: UIColor.white,
        NSAttributedString.Key.font: UIFont(name: "HelveticaNeue-CondensedBlack", size: 40)!,
        NSAttributedString.Key.strokeWidth: -3.0]

Swift NSAttributedStringKey 没有正确应用前景色

Swift NSAttributedStringKey not applying foreground color correctly

ios

swift

nsattributedstringkey