Swift version: 5.4
Navigation bars are one of the most common user interface components in iOS, so being able to add buttons to them is something you'll do a lot. You can add buttons to the left and right side of a navigation bar, and you can add more than one to either side.
Note: usually bar button items don't belong to the
UINavigationBar directly. Instead, they belong to a
UINavigationItem that is currently active on the navigation bar, which in turn is usually owned by the view controller that is currently active on the screen.
So, to create bar button items for your view controller, you would add code like this to the
viewDidLoad() method of a view controller:
navigationItem.leftBarButtonItem = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addTapped)) navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Add", style: .plain, target: self, action: #selector(addTapped))
That will call the
addTapped() method on the current view controller when either button is tapped. Note that the first one uses a standard system icon (recommended when it's available!) and the second one uses text.
Like I said, you can attach more than one bar button item to either side of the navigation bar, like this:
let add = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(addTapped)) let play = UIBarButtonItem(title: "Play", style: .plain, target: self, action: #selector(playTapped)) navigationItem.rightBarButtonItems = [add, play]
Because navigation bar items are attached to view controllers rather than the bar itself, UIKit is able to animate them sliding in and out as view controllers are pushed and popped from a navigation controller – it just replaces the buttons from the existing controller with the buttons from the new controller.
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