How to make NSMutableAttributedString responsive with dynamic type text from settings app

Question

let dictTitleColor = [NSAttributedStringKey.foregroundColor: UIColor.LTColor()]
let titleAttributedString = NSMutableAttributedString(string: title, attributes: dictTitleColor)
alert.setValue(titleAttributedString, forKey: "attributedTitle")

When I Increase the font size of the device the title string dont increase i have set this string in alertview controller ? So How to make This Responsive to font size Change ?

Inder Kumar Rathore · Answer 1 · 2020-10-13T14:56:26.067

3

let dictTitleColor = [NSAttributedStringKey.foregroundColor : UIColor.green,
                      NSAttributedStringKey.font : UIFont.preferredFont(forTextStyle: .headline)]
let titleAttributedString = NSMutableAttributedString(string: title, attributes: dictTitleColor)
alert.setValue(titleAttributedString, forKey: "attributedTitle")

NOTE: This will fail if the popup is presented and then user changed the font size in the accessibility settings. For this case you might need to listen to the UIContentSizeCategory.didChangeNotification and update the font size there.

e.g.

NotificationCenter.default.addObserver(self, selector: #selector(preferredContentSizeChanged(_:)), name: UIContentSizeCategory.didChangeNotification, object: nil)

The method

@objc func preferredContentSizeChanged(_ notification: Notification) {
  let dictTitleColor = [NSAttributedStringKey.foregroundColor : UIColor.green,
                        NSAttributedStringKey.font : UIFont.preferredFont(forTextStyle: .headline)]
  let titleAttributedString = NSMutableAttributedString(string: title, attributes: dictTitleColor)
  alert.setValue(titleAttributedString, forKey: "attributedTitle")
}

edited Oct 13 '20 at 14:56

answered Nov 30 '17 at 09:31

Inder Kumar Rathore

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Setting .Headline Font Will Change The Default Font . What Is The Default Font for AttributedString ? – Amey Nov 30 '17 at 12:47
I don't know what's the default but if I've to guess then it would be `UIFont.systemFont` – Inder Kumar Rathore Dec 01 '17 at 07:26
If i set at function preferredContentSizeChanged new alert would popup above the old one ! – Amey Dec 07 '17 at 06:47
You don't have to show the alert again, just change the font size of the existing alert – Inder Kumar Rathore Dec 07 '17 at 09:09
If alert is already Opened and user change the font size the above code wouldn't work . – Amey Dec 08 '17 at 06:00
Did you hold the reference of the alert shown? and did your callback is being called? – Inder Kumar Rathore Dec 08 '17 at 06:16
how to hold reference of the alert shown would be a great help if you can demonstrate it using code !. – Amey Dec 08 '17 at 08:20
Since Swift 4.2 some notification names has changed. Use 'UIContentSizeCategory.didChangeNotification' instead of 'NSNotification.Name.UIContentSizeCategoryDidChange'. – Peter Kreinz Oct 13 '20 at 10:37

Isha · Answer 2 · 2022-02-18T09:09:16.080

To adapt dynamic font size and enable accessibility for attributed text you can use the following function.

static func convertHtml(string: String?) -> NSAttributedString? {
    
    guard let string = string else {return nil}
    
    guard let data = string.data(using: .utf8) else {
        return nil
    }
    
    do {
        let attrStr = try NSAttributedString(data: data,
                                      options: [.documentType: NSAttributedString.DocumentType.html, .characterEncoding: String.Encoding.utf8.rawValue],
                                      documentAttributes: nil)
        let range = NSRange(location: 0, length: attrStr.length)
        let str = NSMutableAttributedString(attributedString: attrStr)
        
        str.enumerateAttribute(NSAttributedString.Key.font, in: NSMakeRange(0, str.length), options: .longestEffectiveRangeNotRequired) {
            (value, range, stop) in
            if let font = value as? UIFont {
                
                let userFont =  UIFontDescriptor.preferredFontDescriptor(withTextStyle: .title2)
                let pointSize = userFont.withSize(font.pointSize)
                let customFont = UIFont.systemFont(ofSize: pointSize.pointSize)
                let dynamicText = UIFontMetrics.default.scaledFont(for: customFont)
                str.addAttribute(NSAttributedString.Key.font,
                                         value: dynamicText,
                                         range: range)
            }
        }

        str.addAttribute(NSAttributedString.Key.underlineStyle, value: 0, range: range)
        
        return NSAttributedString(attributedString: str.attributedSubstring(from: range))
    } catch {}
    return nil
    
}

Then you can you this on ur textview.

let htmToStringText = convertHtml(string: html))
            
  self.bodyTextView.isEditable = false
  self.bodyTextView.isAccessibilityElement = true
  self.bodyTextView.adjustsFontForContentSizeCategory = true
  self.bodyTextView.attributedText = htmToStringText
  self.bodyTextView.accessibilityAttributedLabel = htmToStringText

How to make NSMutableAttributedString responsive with dynamic type text from settings app

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