更改导航栏后退按钮的厚度

Question

I looked everywhere and can't seem to find how to change the thickness of the navigation bar's back button text. I want it to be thinner.

Also, while we are talking about thickness, how would you go about changing the navigation bar's title thickness as well?

Thank you!

Answer 1

You can modify the font style by adjusting the titleTextAttributes on the navigation bar and the back-button item.

Default Style (iOS 8)

Adapting Size and Thickness (iOS < 8.2)

Prior to iOS version 8.2 the only way to adjust the weight of a font is to choose one of its variants like HelveticaNeue-Light or HelveticaNeue-Bold or by using

UIFont.boldSystemFontOfSize(_ fontSize: CGFloat)

There is, however, no equivalent lightSystemFontOfSize factory function. To reduce the weight and size of the back button and title text you could use something like this (inside a presenting view controller)

let rootController = UIViewController()
rootController.navigationItem.backBarButtonItem = UIBarButtonItem(title: "Back",
    style: .Plain, target: nil, action: nil)
rootController.navigationItem.backBarButtonItem?.setTitleTextAttributes(
    [NSFontAttributeName: UIFont(name: "HelveticaNeue-Light", size: 15)!],
    forState: .Normal)

let detailController = UIViewController()
detailController.title = "Title"

let navController = UINavigationController()
navController.viewControllers = [rootController, detailController]
navController.navigationBar.titleTextAttributes = [
    NSFontAttributeName: UIFont(name: "HelveticaNeue", size: 18)!]

presentViewController(navController, animated: true, completion: nil)

which produces the following style

Adapting Size and Thickness (iOS >= 8.2)

Since iOS version 8.2 you can initialize system fonts with a weight attribute.

UIFont.systemFontOfSize(_ fontSize: CGFloat, weight weight: CGFloat)

There is a set of predefined weight constants that can be found in Apple's official documentation .

Building upon the previous example you could do something like this

let rootController = UIViewController()
rootController.navigationItem.backBarButtonItem = UIBarButtonItem(title: "Back",
    style: .Plain, target: nil, action: nil)
rootController.navigationItem.backBarButtonItem?.setTitleTextAttributes(
    [NSFontAttributeName: UIFont.systemFontOfSize(15, weight: UIFontWeightThin)],
    forState: .Normal)

let detailController = UIViewController()
detailController.title = "Title"

let navController = UINavigationController()
navController.viewControllers = [rootController, detailController]
navController.navigationBar.titleTextAttributes = [
    NSFontAttributeName: UIFont.systemFontOfSize(18, weight: UIFontWeightLight)]

which ultimately results in a style like this