How to Align Child View Content Below a Custom Header in UITabBarController?

You can solve this by shifting the layout of your child view controllers so that their views start below your custom header. A common, cleaner approach is to leverage the safe area insets rather than trying to “reach up” to the parent’s view. In your custom UITabBarController (TabBarLayout), after you add your header view, you can adjust its additionalSafeAreaInsets so that each child controller’s view automatically starts below the header.

For example, in TabBarLayout.swift, update viewDidLoad like this:

SWIFTCopied
override func viewDidLoad() {
    super.viewDidLoad()
    
    viewHeader.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(viewHeader)
    
    // Setup header constraints
    NSLayoutConstraint.activate([
        viewHeader.leftAnchor.constraint(equalTo: view.leftAnchor),
        viewHeader.rightAnchor.constraint(equalTo: view.rightAnchor),
        viewHeader.topAnchor.constraint(equalTo: view.topAnchor),
        viewHeader.heightAnchor.constraint(equalToConstant: 100)
    ])
    
    // Adjust safe area so child view controllers layout below header.
    // This will shift their safeAreaLayoutGuide.top to viewHeader.bottom.
    additionalSafeAreaInsets.top = 100
}

By setting additionalSafeAreaInsets.top to 100 (the height of your header), any child view (like the one in Buy.storyboard) that uses the safe area layout guide will automatically appear below the header. In your BuyController, if you lay out your views relative to the safe area (for example, by pinning your test label’s topAnchor to view.safeAreaLayoutGuide.topAnchor), it will be positioned immediately below your header.

This approach avoids manually setting constraints between the header in the tab bar controller and views in each child controller. It also makes the layout more robust (for example, automatically working correctly with the status bar or other elements).

If you need to manually set a constraint in BuyController relative to the header, you’d have to expose the header view (and ensure proper timing when the layout has been performed), but leveraging the safe area is generally preferred.