Swift - 使用 Storyboard 的属性文本功能在以编程方式设置字体大小并运行模拟器时全部重置

Question

On the storyboard I created a text view. Inserted two paragraphs of text content inside textview. Selected custom attributes on the storyboard and made some words bold. When I run the simulator, everything is ok. But when I set the font size programmatically with respect to the "view.frame.height", the bold words which I set on the storyboard resets to regular words.

Code: "abcTextView.font = abcTextView.font?.withSize(self.view.frame.height * 0.021)"

I couldn't get past this issue. How can I solve this?

Answer 1

The problem is that you're working with an AttributedString. Take a look at Manmal's excellent answer here if you want more context, and an explanation of how the code works:

NSAttributedString, change the font overall BUT keep all other attributes?

Here's an easy application of the extension he provides, to put it in the context of your problem:

class ViewController: UIViewController {

    @IBOutlet weak var myTextView: UITextView!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.

        let newString = NSMutableAttributedString(attributedString: myTextView.attributedText)
        newString.setFontFace(font: UIFont.systemFont(ofSize: self.view.frame.height * 0.033))
        myTextView.attributedText = newString

    }

}

extension NSMutableAttributedString {
    func setFontFace(font: UIFont, color: UIColor? = nil) {
        beginEditing()
        self.enumerateAttribute(
            .font,
            in: NSRange(location: 0, length: self.length)
        ) { (value, range, stop) in

            if let f = value as? UIFont,
              let newFontDescriptor = f.fontDescriptor
                .withFamily(font.familyName)
                .withSymbolicTraits(f.fontDescriptor.symbolicTraits) {

                let newFont = UIFont(
                    descriptor: newFontDescriptor,
                    size: font.pointSize
                )
                removeAttribute(.font, range: range)
                addAttribute(.font, value: newFont, range: range)
                if let color = color {
                    removeAttribute(
                        .foregroundColor,
                        range: range
                    )
                    addAttribute(
                        .foregroundColor,
                        value: color,
                        range: range
                    )
                }
            }
        }
        endEditing()
    }
}