Adding a UIView to the bottom of a UICollectionViewController - ios

Question

I have a UICollectionViewController embedded inside a UINavigationController which in turn embedded inside a UITabBarController.
I want to add a UIView to the UICollectionViewController just above the tab bar (shown by red rectangle).
I have the UIView created separately as a nib file.
import UIKit
class BottomView: UIView {
#IBOutlet var view: UIView!
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
commonInit()
}
override init(frame: CGRect) {
super.init(frame: frame)
commonInit()
}
fileprivate func commonInit() {
Bundle.main.loadNibNamed("BottomView", owner: self, options: nil)
view.frame = self.frame
view.autoresizingMask = [.flexibleHeight, .flexibleWidth]
addSubview(view)
}
}
And I initialize and add it in the UICollectionViewController like so.
class CollectionViewController: UICollectionViewController {
fileprivate var bottomView: BottomView!
override func viewDidLoad() {
super.viewDidLoad()
let yPos = view.bounds.height - (tabBarController!.tabBar.frame.size.height + 44)
bottomView = BottomView(frame: CGRect(x: 0, y: yPos, width: view.bounds.width, height: 44))
collectionView?.addSubview(bottomView)
}
// ...
}
I figured if I substract the combined height of the bottom view plus the tab bar from the entire view's height, I should be able to get the correct y position value. But it's not happening. The view is getting added but way off screen.
How do I calculate the correct y position without hardcoding it?
Example demo project

Answer 1

I would suggest adding the BottomView to the UICollectionViewController's view rather than to the collection view itself. This is part of the problem you're having.
You're also trying to set the frame of the BottomView in the viewDidLoad() method using values from view.bounds. The CGRect will return (0.0, 0.0, 0.0, 0.0) at this point because the layout has yet to take place, which is most likely why your positioning is off. Try moving your layout logic to the viewWillLayoutSubviews() method and see if that helps.
A better approach would be by setting auto layout constrains rather than defining a frame manually, this will take a lot of the leg work out for you.
Here's a quick example:
self.bottomView.translatesAutoresizingMaskIntoConstraints = false
self.view.insertSubview(self.bottomView, at: 0)
self.bottomView.bottomAnchor.constraint(equalTo: self.view.layoutMarginsGuide.bottomAnchor).isActive = true
self.bottomView.leadingAnchor.constraint(equalTo: self.view.leadingAnchor).isActive = true
self.bottomView.trailingAnchor.constraint(equalTo: self.view.trailingAnchor).isActive = true
self.bottomView.heightAnchor.constraint(equalToConstant: 100.0).isActive = true
You can apply autolayout logic in your viewDidLoad() and it should work correctly.
You can find some more information on setting autolayout constraints programatically here:
https://developer.apple.com/library/content/documentation/UserExperience/Conceptual/AutolayoutPG/ProgrammaticallyCreatingConstraints.html

Answer 2

Sounds what you want to achieve is exactly the footer view for the UICollectionView.
A footerView is like a view that will stick to the bottom of the collectionView and wont move with the cells.
This will help you add a footer View: https://stackoverflow.com/a/26893334/3165112
Hope that helps!