How to prevent Large Title from Collapsing

问题

The question is simple, how can I prevent a Large Title Navigation Bar from collapse when a scrollview scrolls down?

My navigation must have a large navigation bar at all times... so when a scrollview scroll, the navigation bar shouldn't collapse up, it should stay the same size, how can I do that?

This is how I set the largeTitle preferences

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)
    self.navigationItem.hidesBackButton = true
    presenter.expandForSimulatorLayoutIfNeeded()

}


func expandForSimulatorLayoutIfNeeded(){
            if !isExpanded{
        topMenu = TopMenu(frame: expandedNavigationFrame, interactor: interactor)
        oldNavigationBarFrame = navigationBar.frame
        self.navigationBar.addSubview(topMenu)
    }

    if #available(iOS 11.0, *) {
        self.navigationBar.prefersLargeTitles = true
    } else {
        self.navigationBar.frame = expandedNavigationFrame
    }

    let topConstraint = NSLayoutConstraint(item: topMenu, attribute: .top, relatedBy: .equal, toItem: navigationBar, attribute: .top, multiplier: 1, constant: 0)
    let leadingConstraint = NSLayoutConstraint(item: topMenu, attribute: .leading, relatedBy: .equal, toItem: navigationBar, attribute: .leading, multiplier: 1, constant: 0)
    let widthConstraint = NSLayoutConstraint(item: topMenu, attribute: .width, relatedBy: .equal, toItem: self.navigationBar, attribute: .width, multiplier: 1, constant: 0)
    let bottomConstraint = NSLayoutConstraint(item: topMenu, attribute: .bottom, relatedBy: .equal, toItem: navigationBar, attribute: .bottom, multiplier: 1, constant: 0)
    topMenu.translatesAutoresizingMaskIntoConstraints = false
    NSLayoutConstraint.activate([leadingConstraint, widthConstraint, topConstraint, bottomConstraint])

}

回答1:

A workaround i figured out is to add a placeholder view that is not CollectionView/TableView as the very first view in ViewController's base view. This first view will be attached to the top of the safeArea, height can be zero.

Using Storyboard/Xib:

See the below screenshot for this view with constraints

Next add another UIView to serve as a container view for your TableView/CollectionView. This container's top will be attached to bottom of the placeholder view. See the below screenshot for constraints of container view and TableView/CollectionView.

The key here is the first view in the view hierarchy as the navigation bar will check that to set the collapsing effect. Once it does not find it as a CollectionView/TableView, it will not collapse on scrolling.

Programmatically:

If you are setting up view's programmatically then you just need to add a placeholder view at the top.

e.g,

self.view.addSubview(UIView(frame: .zero))
self.view.addSubview(tableView) // or collectionView

回答2:

To prevent the large tile nav bar from collapsing simply add a second view to your UIViewController in the viewDidLoad method.

view.addSubview(UIView())

For whatever reason, this breaks the link between your the UIScrollView and the nav bar.

回答3:

If someone arrives here from SwiftUI land, this is a good way to keep your lists in large title mode.

// your content view ...

    var body: some View {
        VStack {
            PreventCollapseView()
            List {
                ForEach(things, id: \.self) { thing in
                    Text(thing.name)
                }
            }
        }
        .navigationBarTitle("All the things")
    }


// end of view


struct PreventCollapseView: View {

    private var mostlyClear = Color(UIColor(white: 0.0, alpha: 0.0005))

    var body: some View {
        Rectangle()
            .fill(mostlyClear)
            .frame(minWidth: 0, maxWidth: .infinity, minHeight: 0, maxHeight: 1)
    }
}

来源：https://stackoverflow.com/questions/50915191/how-to-prevent-large-title-from-collapsing