View on Top of UITabBar

Question

Similar to what the Spotify or Apple Music app does when a song is playing, it places a custom view on top of the UITabBar:

Solutions I've tried:

1. UITabBarController in a ViewController with a max-sized Container View, and the custom view on top of the Container View49pt above the Bottom Layout Guide: Problem: Any content in ViewControllers embedded in the UITabBarController constrained to the bottom don't show because they're hidden behind the custom layout. I've tried overriding size forChildContentContainer in UITabBarController, tried updating the bottom layout guide, Nothing. I need to resize the frame of container view of the UITabBarController.

2. Tried #1 again, but tried solving the problem of content hiding behind it by increasing the size of UITabBar, and then using ImageInset on every TabBarItem to bring it down, and adding my custom view on top of the UITabBar. Hasn't worked really well. There are going to be times when I want to hide my custom view.

3. UITabBarController as root, with each children being a ViewController with a Container View + my custom view: But now I have multiple instances of my custom view floating around. If I want to change a label on it, have to change it to all views. Or hide, etc.

4. Override the UITabBar property of UITabBarController and return my custom UITabBar (inflated it with a xib) that has a UITabBar + my custom view. Problem: Probably the most frustrating attempt of all. If you override that property with an instance of class MyCustomTabBar : UITabBar {}, no tab shows up! And yes, I set the delegate of myCustomTabBar to self.

Leaning towards #3, but looking for a better solution.

Answer 1

This is actually very easy if you subclass UITabBarController and add your view programmatically. Using this technique automatically supports rotation and size changes of the tab bar, regardless of which version you are on.

class CustomTabBarController: UITabBarController {
  override func viewDidLoad() {
    super.viewDidLoad()

    //...do some of your custom setup work
    // add a container view above the tabBar
    let containerView = UIView()
    containerView.backgroundColor = .red
    view.addSubview(containerView)
    containerView.translatesAutoresizingMaskIntoConstraints = false
    containerView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
    containerView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true

    // anchor your view right above the tabBar
    containerView.bottomAnchor.constraint(equalTo: tabBar.topAnchor).isActive = true

    containerView.heightAnchor.constraint(equalToConstant: 50).isActive = true
  }
}

Answer 2

I got it!

In essence, I increased the size of the original UITabBar to accomodate a custom view (and to shrink the frame of the viewcontrollers above), and then adds a duplicate UITabBar + custom view right on top of it.

Here's the meat of what I had to do. I uploaded a functioning example of it and can be found in this repo:

class TabBarViewController: UITabBarController {

    var currentlyPlaying: CurrentlyPlayingView!
    static let maxHeight = 100
    static let minHeight = 49
    static var tabbarHeight = maxHeight

    override func viewDidLoad() {
        super.viewDidLoad()

        currentlyPlaying = CurrentlyPlayingView(copyFrom: tabBar)
        currentlyPlaying.tabBar.delegate = self

        view.addSubview(currentlyPlaying)
        tabBar.isHidden = true
    }
    override func viewWillAppear(_ animated: Bool) {
        super.viewWillAppear(animated)

        currentlyPlaying.tabBar.items = tabBar.items
        currentlyPlaying.tabBar.selectedItem = tabBar.selectedItem
    }
    func hideCurrentlyPlaying() {
        TabBarViewController.tabbarHeight = TabBarViewController.minHeight
        UIView.animate(withDuration: 0.5, animations: {
            self.currentlyPlaying.hideCustomView()
            self.updateSelectedViewControllerLayout()
        })
    }
    func updateSelectedViewControllerLayout() {
        tabBar.sizeToFit()
        tabBar.sizeToFit()
        currentlyPlaying.sizeToFit()
        view.setNeedsLayout()
        view.layoutIfNeeded()
        viewControllers?[self.selectedIndex].view.setNeedsLayout()
        viewControllers?[self.selectedIndex].view.layoutIfNeeded()
    }
}

extension UITabBar {

    open override func sizeThatFits(_ size: CGSize) -> CGSize {
        var sizeThatFits = super.sizeThatFits(size)
        sizeThatFits.height = CGFloat(TabBarViewController.tabbarHeight)
        return sizeThatFits
    }
}