Passen Sie die Navigationsleiste Titel Schriftgröße anpassen von text

Können Sie erstellen ein UILabel und legen Sie es auf UINavigationItem ist titleView. Siehe Apple doc: https://developer.apple.com/library/ios/documentation/UIKit/Reference/UINavigationItem_Class/#//apple_ref/occ/instp/UINavigationItem/titleView

Für die erstellten UILabel, können Sie die adjustsFontSizeToFitWidth & minimumScaleFactor Eigenschaften zu lassen, passen die Titel. Doc:
https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UILabel_Class/#//apple_ref/occ/instp/UILabel/adjustsFontSizeToFitWidth

Einige codes:

- (void)setMyTitle:(NSString *)title
{
    UILabel *titleLabel = [[UILabel alloc] initWithFrame:CGRectMake(0, 0, self.navigationController.view.bounds.size.width - 100, 44)];
    titleLabel.text = title;
    titleLabel.font = [UIFont systemFontOfSize:16];
    titleLabel.textColor = ...
    ...
    self.navigationItem.titleView = titleLabel;
}

Swift 5

private var isFirst = true
override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    guard isFirst else {
    return
    }
    isFirst = false
    //Adjust Navigation Title by text
    if let navigationController = navigationController {
    let bar = navigationController.navigationBar
    var minX: CGFloat = 0
    var maxX: CGFloat = bar.bounds.width
    if let lastLeft = navigationItem.leftBarButtonItems?.last, let leftView = lastLeft.view, let buttonBarStackViewFrame = leftView.superview?.frame {
        minX = buttonBarStackViewFrame.maxX
    }
    if let firstRight = navigationItem.rightBarButtonItems?.first, let rightView = firstRight.view, let buttonBarStackViewFrame = rightView.superview?.frame {
        maxX = buttonBarStackViewFrame.minX
    }

    let titleLabel = UILabel(frame: CGRect(x: 0, y: 0, width: maxX - minX, height: bar.bounds.height))
    titleLabel.text = LocStr(.favorite_master_title)
    titleLabel.adjustsFontSizeToFitWidth = true
    titleLabel.minimumScaleFactor = 0.3
    titleLabel.textColor = UIColor.white
    titleLabel.textAlignment = .center
    if UIDevice.current.modelName.contains(PLUS) {
        titleLabel.font = UIFont(name: GENERAL_FONT_NAME, size: PLUS_NAVIGATION_BAR_TITLE_FONT)!
    } else {
        titleLabel.font = UIFont(name: GENERAL_FONT_NAME, size: GENERAL_NAVIGATION_BAR_TITLE_FONT)!
    }
    navigationItem.titleView = titleLabel
    }
}

mit einer Erweiterung

extension UIBarButtonItem {
    var view: UIView? {
        return value(forKey: "view") as? UIView
    }
}