Ggtcf

I am experiencing a problem with the new way of adding search bar to the navigation item.

As you can see in the picture below, there are two UIViewControllers one after the other, and both have the search bar. The problem is the animation, which is ugly when search bar is visible on the first view controller but not on the second one. The area occupied by the search bar stays on the screen and suddenly disappears.

The code is very basic (no other changes in the project were made):

(I write primarily in C#, so there might be errors in this code.)

ViewController.swift:

import UIKit

class ViewController: UITableViewController, UISearchResultsUpdating 

override func loadView() 
 super.loadView()

 definesPresentationContext = true;

 navigationController?.navigationBar.prefersLargeTitles = true;
 navigationItem.largeTitleDisplayMode = .automatic;
 navigationItem.title = "VC"

 tableView.insetsContentViewsToSafeArea = true;
 tableView.dataSource = self;

 refreshControl = UIRefreshControl();
 refreshControl?.addTarget(self, action: #selector(ViewController.handleRefresh(_:)), for: UIControlEvents.valueChanged)
 tableView.refreshControl = refreshControl;

 let stvc = UITableViewController();
 stvc.tableView.dataSource = self;

 let sc = UISearchController(searchResultsController: stvc);
 sc.searchResultsUpdater = self;
 navigationItem.searchController = sc;


override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell 
 var cell = tableView.dequeueReusableCell(withIdentifier: "cell1");
 if (cell == nil) 
 cell = UITableViewCell(style: .default, reuseIdentifier: "cell1");
 
 cell?.textLabel?.text = "cell " + String(indexPath.row);
 return cell!;


override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int 
 return 20;


override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) 
 let vc = ViewController();
 navigationController?.pushViewController(vc, animated: true);


@objc func handleRefresh(_ refreshControl: UIRefreshControl) 
 DispatchQueue.main.asyncAfter(deadline: .now() + .seconds(2), execute: 
 refreshControl.endRefreshing();
 )


func updateSearchResults(for searchController: UISearchController) 

AppDelegate.swift:

import UIKit

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate 

var window: UIWindow?

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool 

 window = UIWindow(frame: UIScreen.main.bounds);
 window?.rootViewController = UINavigationController(rootViewController: ViewController());
 window?.makeKeyAndVisible();

 UINavigationBar.appearance().barTintColor = UIColor.red;

 return true

Ideas?

It looks like Apple still needs to iron out the use of the UISearchBar in the new large title style. If the UIViewController you push to doesn't have its navigationItem.searchController set, the animation works fine. When navigating between two instances of UIViewController that both have a searchController set, you get the issue you describe where the height of the navigation bar jumps.

You can solve (work around) the problem by creating the UISearchController every time viewDidAppear gets called (instead of creating it in loadView) and setting navigationItem.searchController to nil on viewDidDisappear.

override func viewDidAppear(_ animated: Bool) 
 super.viewDidAppear(animated)

 DispatchQueue.main.async 
 let stvc = UITableViewController()
 stvc.tableView.dataSource = self

 let sc = UISearchController(searchResultsController: stvc)
 sc.searchResultsUpdater = self
 self.navigationItem.searchController = sc
 


override func viewDidDisappear(_ animated: Bool) 
 super.viewDidDisappear(animated)

 self.navigationItem.searchController = nil

The reason for the asynchronous dispatch is that when setting the navigationItem.searchController inline in the viewDidAppear method, an exception is raised:

Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Only one palette with a top boundary edge can be active outside of a transition. Current active palette is <_UINavigationControllerManagedSearchPalette: 0x7fad67117e80; frame = (0 116; 414 0); layer = <CALayer: 0x60400002c8e0>>'

I know this is only a work around, but hopefully this will help you for now, until Apple solves the issue with navigating between two view controllers that both have a UISearchController set on their navigationItem.

My solution for this problem is to update the constraint that is keeping the UISearchBar visible, when the UIViewController is being dismissed. I was not able to use silicon_valley's solution as even with the asynchronous dispatch I was getting the crash he mentioned. This is admittedly a pretty messy solution but Apple hasn't made this easy.

The code below assumes you have a property containing a UISearchController instance within your UIViewController subclass called searchController

override func viewWillDisappear(_ animated: Bool) 
 super.viewWillDisappear(animated)

 if
 animated
 && !searchController.isActive
 && !searchController.isEditing
 && navigationController.map($0.viewControllers.last != self) ?? false,
 let searchBarSuperview = searchController.searchBar.superview,
 let searchBarHeightConstraint = searchBarSuperview.constraints.first(where: 
 $0.firstAttribute == .height
 && $0.secondItem == nil
 && $0.secondAttribute == .notAnAttribute
 && $0.constant > 0
 ) 

 UIView.performWithoutAnimation 
 searchBarHeightConstraint.constant = 0
 searchBarSuperview.superview?.layoutIfNeeded()
 
 

You can remove the performWithoutAnimation and layoutIfNeeded, and it will still animate; however I found the animation was never triggered the first time, and it doesn't look that great anyway.

I hope Apple fixes this in a later iOS release, the current release is 12.1.4 at the time of writing.

The accepted answer does solve the problem for some situations, but I was experiencing it resulting in the complete removal of the navigationItem in the pushed view controller if the first search bar was active.

I've come up with another workaround, similar to the answer by stu, but requiring no meddling with constraints. The approach is to determine, at the point of the segue, whether the search bar is visible. If it is, we instruct the destination view controller to make its search bar visible from load. This means that the navigation item animation behaves correctly:

Assuming the two view controllers are called UIViewController1 and UIViewController2, where 1 pushes 2, the code is as follows:

class ViewController1: UITableViewController 

 override func viewDidLoad() 
 super.viewDidLoad()

 let searchController = UISearchController(searchResultsController: nil)
 searchController.obscuresBackgroundDuringPresentation = false
 navigationItem.searchController = searchController

 definesPresentationContext = true
 

 override func prepare(for segue: UIStoryboardSegue, sender: Any?) 
 if let viewController2 = segue.destination as? ViewController2, let searchController = navigationItem.searchController 

 // If the search bar is visible (but not active, which would make it visible but at the top of the view)
 // in this view controller as we are preparing to segue, instruct the destination view controller that its
 // search bar should be visible from load.
 viewController2.forceSearchBarVisibleOnLoad = !searchController.isActive && searchController.searchBar.frame.height > 0
 
 

class ViewController2: UITableViewController 

 var forceSearchBarVisibleOnLoad = false

 override func viewDidLoad() 
 super.viewDidLoad()

 let searchController = UISearchController(searchResultsController: nil)
 searchController.obscuresBackgroundDuringPresentation = false
 navigationItem.searchController = searchController

 // If on load we want to force the search bar to be visible, we make it so that it is always visible to start with
 if forceSearchBarVisibleOnLoad 
 navigationItem.hidesSearchBarWhenScrolling = false
 
 

 override func viewDidAppear(_ animated: Bool) 
 super.viewDidAppear(animated)
 // When the view has appeared, we switch back the default behaviour of the search bar being hideable.
 // The search bar will already be visible at this point, thus achieving what we aimed to do (have it
 // visible during the animation).
 navigationItem.hidesSearchBarWhenScrolling = true
 

I have added this code in viewDidLoad() and it's working, when I moved in b/w of tabs

searchController.dimsBackgroundDuringPresentation