UIViewcontroller disappear after switch tabs UITabBarController - ios

Question

I'm working on an app that uses UITabBarController and sudenlly one tabItem stops to appear. Then I start to investigate and end up with a problem related with UISearchController and UITabBarController.
To isolate the problem a build a simple app to demostrate the situation.
This is how I instanciate the TabBar at didFinishLaunchingWithOptions :
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
self.window = UIWindow(frame: UIScreen.main.bounds)
self.window?.backgroundColor = .white
let first:SearchController = {
let sc = SearchController()
sc.tabBarItem = UITabBarItem(title: "First", image: UIImage(named:"iphone"), tag: 0)
return sc
}()
let second:SecondViewController = {
let s = SecondViewController()
s.tabBarItem = UITabBarItem(title: "Second", image: UIImage(named:"iphone"), tag: 1)
return s
}()
let tabBar = UITabBarController()
let controllers = [first, second]
tabBar.viewControllers = controllers.map {
UINavigationController(rootViewController: $0)
}
self.window?.rootViewController = tabBar
self.window?.makeKeyAndVisible()
return true
}
This is the viewController with UISearchController:
class SearchController: UIViewController {
var matchingItems:[String] = [] {
didSet{
self.tableView.reloadData()
}
}
lazy var searchController:UISearchController = UISearchController(searchResultsController: nil)
lazy var tableView: UITableView = { [unowned self] in
let tv = UITableView(frame: CGRect.zero, style: .grouped)
tv.translatesAutoresizingMaskIntoConstraints = false
tv.delegate = self
tv.dataSource = self
tv.register(UITableViewCell.self, forCellReuseIdentifier: "id")
return tv
}()
override func viewDidLoad() {
super.viewDidLoad()
title = "First"
view.addSubview(self.tableView)
self.navigationItem.searchController = searchController
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
self.perform(#selector(showKeyboard), with: nil, afterDelay: 0.1)
}
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
searchController.searchBar.resignFirstResponder()
}
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
let layout = self.view.safeAreaLayoutGuide
tableView.topAnchor.constraint(equalTo: layout.topAnchor).isActive = true
tableView.bottomAnchor.constraint(equalTo: layout.bottomAnchor).isActive = true
tableView.rightAnchor.constraint(equalTo: layout.rightAnchor).isActive = true
tableView.leftAnchor.constraint(equalTo: layout.leftAnchor).isActive = true
}
#objc func showKeyboard() {
self.searchController.searchBar.becomeFirstResponder()
self.searchController.searchBar.text = ""
}
}
In run time, when system finished rendering this view controller, the debug console print this:
SearchBar+TabBar[15454:895018] [MC] Reading from private effective user settings.
2018-04-22 12:07:19.595887-0300 SearchBar+TabBar[15454:895018] +[CATransaction synchronize] called within transaction
2018-04-22 12:07:19.608090-0300 SearchBar+TabBar[15454:895018] +[CATransaction synchronize] called within transaction
2018-04-22 12:07:19.608269-0300 SearchBar+TabBar[15454:895018] +[CATransaction synchronize] called within transaction
2018-04-22 12:07:19.608516-0300 SearchBar+TabBar[15454:895018] +[CATransaction synchronize] called within transaction
Searching on the stackoverflow I found that this message +[CATransaction synchronize] called within transaction
is related to rendering more than one animation in the main thread.
I'm wondering if this viewcontroller visualisation problem is related to that. So I commented the searchController instantiation line in SearchController class:
self.navigationItem.searchController = searchController
Now the UITabBarController works perfectly without the UISearchController in my first view controller.
My questions are:
Is there another way to instanciate UISearchController to avoid
this?
If yes, how should I do that?
GitHub repository with the sample code: sample code

Answer 1

In Your TabBarController class implement this function:
func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool
In this function you should check if Controller with searchBar was selected before and make SearchController inactive
func tabBarController(_ tabBarController: UITabBarController, shouldSelect viewController: UIViewController) -> Bool {
if (tabBarController.selectedIndex == ControllerWithSearchBarIndex) {
((viewControllers![ControllerWithSearchBarIndex] as! UINavigationController).viewControllers.first! as! ControllerWithSearchBarIndex).searchController.isActive = false
}
return true
}

Answer 2

A friend of my suggests to add UITabBarController as root of UINavigationController in the at didFinishLaunchingWithOptions and it works perfectly and solve the problem:
let tabBar = UITabBarController()
let controllers = [first, second]
tabBar.viewControllers = controllers.map {
UINavigationController(rootViewController: $0)
}
let nav = UINavigationController(rootViewController: tabBar)
nav.isNavigationBarHidden = true
nav.navigationBar.isUserInteractionEnabled = false

Answer 3

Set definesPresentationContext = true on the view controller with the tableView (SearchController in your example). This will allow the UISearchController to remain active when you switch tabs.