SwiftUI: In SplitView, how can I detect if the master view is visible? - swiftui

Question

When SwiftUI creates a SplitView, it adds a toolbar button that hides/shows the Master view. How can I detect this change so that I can resize the font in the detail screen and use all the space optimally?
I've tried using .onChange with geometry but can't seem to get that to work.

Answer 1

If you're using iOS 16 you can use NavigationSplitView with NavigationSplitViewVisibility
Example:
struct MySplitView: View {
#State private var columnVisibility: NavigationSplitViewVisibility = .all
var bothAreShown: Bool { columnVisibility != .detailOnly }
var body: some View {
NavigationSplitView(columnVisibility: $columnVisibility) {
Text("Master Column")
} detail: {
Text("Detail Column")
Text(bothAreShown ? "Both are shown" : "Just detail shown")
}
}
}

Answer 2

After thinkering for a while on this I got to this solution:
struct ContentView: View {
#State var isOpen = true
var body: some View {
NavigationView {
VStack{
Text("Primary")
.onUIKitAppear {
isOpen.toggle()
}
.onAppear{
print("hello")
isOpen.toggle()
}
.onDisappear{
isOpen.toggle()
print("hello: bye")
}
.navigationTitle("options")
}
Text("Secondary").font(isOpen ? .body : .title)
}.navigationViewStyle(.columns)
}
}
The onUIKitAppear is a custom extension suggested by apple to be only executed once the view has been presented to the user https://developer.apple.com/forums/thread/655338?page=2
struct UIKitAppear: UIViewControllerRepresentable {
let action: () -> Void
func makeUIViewController(context: Context) -> UIAppearViewController {
let vc = UIAppearViewController()
vc.delegate = context.coordinator
return vc
}
func makeCoordinator() -> Coordinator {
Coordinator(action: self.action)
}
func updateUIViewController(_ controller: UIAppearViewController, context: Context) {}
class Coordinator: ActionRepresentable {
var action: () -> Void
init(action: #escaping () -> Void) {
self.action = action
}
func remoteAction() {
action()
}
}
}
protocol ActionRepresentable: AnyObject {
func remoteAction()
}
class UIAppearViewController: UIViewController {
weak var delegate: ActionRepresentable?
var savedView: UIView?
override func viewDidLoad() {
self.savedView = UILabel()
if let _view = self.savedView {
view.addSubview(_view)
}
}
override func viewDidAppear(_ animated: Bool) {
delegate?.remoteAction()
}
override func viewDidDisappear(_ animated: Bool) {
view.removeFromSuperview()
savedView?.removeFromSuperview()
}
}
public extension View {
func onUIKitAppear(_ perform: #escaping () -> Void) -> some View {
self.background(UIKitAppear(action: perform))
}
}