Responding to navigation bar height changes during push transition

10
votes

In iOS 11 the search bar will now change the navigation bar height to 56dp when adding a search bar to the navigationItem.titleView

I like the height change and don't intend on forcing the height to stay at 44dp or lower.

unfortunately when transitioning from one view controller to another the pushed view will be drawn with the larger navigation bar in mind and then the bar height is changed after the transition is finished. That looks a little like this:

enter image description here enter image description here

I need a way of getting the navigation controller to recognise the height change during the transition so that it can animate to the smaller size and draw the view correctly.

I have one current fix which I don't like because it's a little jumpy and it's more work the app has to do and also it has to re-evaulate it's views regardless of which view controller it's being pushed from.

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    if #available(iOS 11, *) {
        navigationController?.view.layoutSubviews()
    }
}

So far I haven't found any similar questions on stack overflow, any comments from WWDC and nothing in the official apple documentation. I've seen many apps deal with this however. The apple contacts app will create what looks like two navigation bars and will move between them without animating the height changes and the fb messenger app will perfectly transition between the heights and even allow for the interactive pop transition.

2
iosswiftuinavigationcontrolleruinavigationbar

2 Answers

3
votes

Using this one, it will keep your searchbar's height fixed

if #available(iOS 11.0, *) {
        searchBar.heightAnchor.constraint(equalToConstant: 44.0).isActive = true
    }
1
votes

I tried a lot of different functions. This thing is the only one that really helps

OBJ C: if (@available(iOS 11, *)) { self.navigationController.view.layoutSubviews; }

SWIFT:

if #available(iOS 11, *) {
    self.navigationController.view.layoutSubviews()
 }