Displaying and switching between ViewControllers in another ViewController - ios

Question

I'm basically trying to create a custom UITabBarController since I need some specific functionality. The TabBar itself is done and working, but I don't quite know how to display ViewControllers in this CustomTabBarViewController itself.
Assuming i have the following method:
func tabSelected(_ index: Int) {}
and knowing the height of my TabBar through tabbar.frame.size, how do I instantiate two ViewControllers above the TabBar and switch between them when the tabSelected method is called? A transition animation would be even nicer, but not really necessary.
NOTE: my TabBar doesn't inherit from UITabBarController, only from the regular UIViewController, to avoid further confusion.

Answer 1

Here I created sample project:
CustomTabBarViewController
You should have container view for child ViewControllers
Then you should have array with embed ViewControllers
You should call method in
CustomTabBarViewController which change ViewController inside
container view to ViewController from array of VCs at index which you pass as parameter of this method
Start with declaring outlet collection for your TabBar buttons and also get reference for container view where your ViewControllers will be showed
#IBOutlet var tabBarButtons: [UIButton]!
#IBOutlet weak var container: UIView!
then create array for your tab bar items
var items: [UIViewController]?
next create lazy variables for your controllers
private lazy var aVC: A = {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
return storyboard.instantiateViewController(withIdentifier: "a") as! A
}()
private lazy var bVC: B = {
let storyboard = UIStoryboard(name: "Main", bundle: nil)
return storyboard.instantiateViewController(withIdentifier: "b") as! B
}()
.... this can be simplified by creating method which returns ViewController depending on VC’s identifier
After that append ViewControllers to your items array and also each add as child of your TabBarViewController
override func viewDidLoad() {
super.viewDidLoad()
items = [aVC, bVC]
items!.forEach { addChild($0) }
}
continue with declaring method for setting ViewController
private func setViewController(_ viewController: UIViewController) {
items!.forEach { $0.view.removeFromSuperview(); $0.willMove(toParent: nil) }
container.addSubview(viewController.view)
viewController.view.frame = container.bounds
viewController.view.autoresizingMask = [.flexibleWidth, .flexibleHeight]
viewController.didMove(toParent: self)
}
now add action for your tab bar buttons and get index of button. Then with this index call your tabSelected method
#IBAction func buttonPressed(_ sender: UIButton) {
if let index = tabBarButtons.index(of: sender) {
tabSelected(index)
}
}
inside tabSelected set VC from items depending on index of sender tab bar button
func tabSelected(_ index: Int) {
if let item = items?[index] {
setViewController(item)
}
}
finally in viewDidLoad set first item
override func viewDidLoad() {
...
tabSelected(0)
}
Now you can fully customize your ViewController and make other epic stuff which you know from UITabBarController

Answer 2

Here's another approach:
1. In your CustomTabBarViewController define an array to hold the ViewControllers:
var viewControllers: [UIViewController]
Instantiate the view controllers and add them to the array:
// If you're not using storyboard:
let homeViewController = HomeViewController()
// If using storyboard:
let searchViewController = storyboard.instantiateViewController(withIdentifier: "SearchViewController")
viewControllers = [homeViewController, searchViewController, ...]
2. Define a variable to keep track of the tab button that is selected:
var selectedIndex: Int = 0
3. Implement your tabSelected method like so. I've explained each line in code:
func tabSelected(_ index: Int) {
let previousIndex = selectedIndex
selectedIndex = index
// Use previousIndex to access the previous ViewController from the viewControllers array.
let previousVC = viewControllers[previousIndex]
// Remove the previous ViewController
previousVC.willMove(toParentViewController: nil)
previousVC.view.removeFromSuperview()
previousVC.removeFromParentViewController()
// Use the selectedIndex to access the current ViewController from the viewControllers array.
let vc = viewControllers[selectedIndex]
// Add the new ViewController (Calls the viewWillAppear method of the ViewController you are adding)
addChildViewController(vc)
vc.view.frame = contentView.bounds
// contentView is the main view above your tab buttons
contentView.addSubview(vc.view)
// Call the viewDidAppear method of the ViewController you are adding using didMove(toParentViewController: self)
vc.didMove(toParentViewController: self)
}