在设置->常规->文本大小中，更改文本大小后，我必须退出我自己的应用才能应用这些大小

 [UIFont preferredFontForTextStyle:..]

是否有委托(delegate)或通知通知我的应用重新应用新尺寸？

更新:我尝试了以下但有趣的是，字体大小将在我 BG 并启动应用程序两次后应用。

- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.


[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(fromBg:) name:UIApplicationDidBecomeActiveNotification object:nil];

}


 -(void) fromBg:(NSNotification *)noti{

    self.headline1.font = [UIFont preferredFontForTextStyle:UIFontTextStyleHeadline];
    self.subHeadline.font = [UIFont preferredFontForTextStyle:UIFontTextStyleSubheadline];
    self.body.font = [UIFont preferredFontForTextStyle:UIFontTextStyleBody];
    self.footnote.font = [UIFont preferredFontForTextStyle:UIFontTextStyleFootnote];
    self.caption1.font = [UIFont preferredFontForTextStyle:UIFontTextStyleCaption1];
    self.caption2.font = [UIFont preferredFontForTextStyle:UIFontTextStyleCaption2];
//    [self.view layoutIfNeeded];

}

最佳答案

对于 Swift 5 和 iOS 12，您可以选择以下三种解决方案之一来解决您的问题。

#1。使用 UIContentSizeCategoryAdjusting 的 adjustsFontForContentSizeCategory 属性

UILabel、UITextField 和 UITextView 符合 UIContentSizeCategoryAdjusting 协议(protocol)，因此有一个名为 adjustsFontForContentSizeCategory 的实例属性. adjustsFontForContentSizeCategory 具有以下声明:

A Boolean value indicating whether the object automatically updates its font when the device's content size category changes.

var adjustsFontForContentSizeCategory: Bool { get set }

下面的 UIViewController 实现展示了如何使用 adjustsFontForContentSizeCategory 检测 iOS 设置中的动态字体大小变化并使用react:

import UIKit

class ViewController: UIViewController {

    let label = UILabel()

    override func viewDidLoad() {
        super.viewDidLoad()

        label.text = "Lorem ipsum dolor sit er elit lamet, consectetaur cillium adipisicing pecu, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
        label.numberOfLines = 0
        label.font = .preferredFont(forTextStyle: UIFont.TextStyle.body)
        label.adjustsFontForContentSizeCategory = true
        view.addSubview(label)

        // Auto layout
        label.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = label.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        let verticalConstraint = label.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        let widthConstraint = label.widthAnchor.constraint(equalToConstant: 300)
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint])
    }

}

#2。使用 UIContentSizeCategory 的 didChangeNotification 类型属性

UIContentSizeCategory 有一个名为 didChangeNotification 的类型属性. didChangeNotification 具有以下声明:

Posted when the user changes the preferred content size setting.

static let didChangeNotification: NSNotification.Name

This notification is sent when the value in the preferredContentSizeCategory property changes. The userInfo dictionary of the notification contains the newValueUserInfoKey key, which reflects the new setting.

下面的 UIViewController 实现展示了如何使用 didChangeNotification 检测 iOS 设置中的动态字体大小变化并使用react:

import UIKit

class ViewController: UIViewController {

    let label = UILabel()

    override func viewDidLoad() {
        super.viewDidLoad()

        label.text = "Lorem ipsum dolor sit er elit lamet, consectetaur cillium adipisicing pecu, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
        label.numberOfLines = 0
        label.font = UIFont.preferredFont(forTextStyle: UIFont.TextStyle.body)
        view.addSubview(label)

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

        // Auto layout
        label.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = label.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        let verticalConstraint = label.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        let widthConstraint = label.widthAnchor.constraint(equalToConstant: 300)
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint])
    }

    @objc func preferredContentSizeChanged(_ notification: Notification) {
        label.font = UIFont.preferredFont(forTextStyle: UIFont.TextStyle.body)
        /* perform other operations if necessary */
    }

}

#3。使用 UITraitCollection 的 preferredContentSizeCategory 属性

UITraitCollection 有一个名为 preferredContentSizeCategory 的属性. preferredContentSizeCategory 具有以下声明:

The font sizing option preferred by the user.

var preferredContentSizeCategory: UIContentSizeCategory { get }

With Dynamic Type, users can ask that apps display text using fonts that are larger or smaller than the normal font size defined by the system. For example, a user with a visual impairment might request a larger default font size to make it easier to read text. Use the value of this property to request a UIFont object that matches the user's requested size.

下面的 UIViewController 实现展示了如何使用 preferredContentSizeCategory 检测 iOS 设置中的动态字体大小变化并使用react:

import UIKit

class ViewController: UIViewController {

    let label = UILabel()

    override func viewDidLoad() {
        super.viewDidLoad()

        label.text = "Lorem ipsum dolor sit er elit lamet, consectetaur cillium adipisicing pecu, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua."
        label.numberOfLines = 0
        label.font = UIFont.preferredFont(forTextStyle: UIFont.TextStyle.body)
        view.addSubview(label)

        // Auto layout
        label.translatesAutoresizingMaskIntoConstraints = false
        let horizontalConstraint = label.centerXAnchor.constraint(equalTo: view.centerXAnchor)
        let verticalConstraint = label.centerYAnchor.constraint(equalTo: view.centerYAnchor)
        let widthConstraint = label.widthAnchor.constraint(equalToConstant: 300)
        NSLayoutConstraint.activate([horizontalConstraint, verticalConstraint, widthConstraint])
    }

    override func traitCollectionDidChange(_ previousTraitCollection: UITraitCollection?) {
        super.traitCollectionDidChange(previousTraitCollection)

        if previousTraitCollection?.preferredContentSizeCategory != traitCollection.preferredContentSizeCategory {
            self.label.font = UIFont.preferredFont(forTextStyle: UIFont.TextStyle.body)
            /* perform other operations if necessary */
        }
    }

}

来源:

• useyourloaf.com / Auto Adjusting Fonts for Dynamic Type

关于ios - 如何从 iOS 设置中检测动态字体大小变化？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/18951332/