Support dynamic content updates in SwiftUI

Store content hosting controller reference and update it dynamically
in updateUIViewController(), allowing panel content to change without
recreation.

Resolved #672

Author: scenee

Examples/SamplesSwiftUI/SamplesSwiftUI/UseCases/MainView.swift

@@ -5,23 +5,28 @@ import SwiftUI
 import UIKit
 
 struct MainView: View {
+    enum CardContent: String, CaseIterable, Identifiable {
+        case list
+        case detail
+
+        var id: String { rawValue }
+    }
     @State private var panelLayout: FloatingPanelLayout? = MyFloatingPanelLayout()
     @State private var panelState: FloatingPanelState?
+    @State private var selectedContent: CardContent = .list
 
     var body: some View {
         ZStack {
             Color.orange
                 .ignoresSafeArea()
-                .floatingPanel(
-                    coordinator: MyPanelCoordinator.self
-                ) { proxy in
-                    ContentView(proxy: proxy)
-                }
-                .floatingPanelSurfaceAppearance(.transparent())
-                .floatingPanelLayout(panelLayout)
-                .floatingPanelState($panelState)
-
             VStack(spacing: 32) {
+                Picker("type", selection: $selectedContent) {
+                    ForEach(CardContent.allCases) {
+                        type in
+                        Text(type.rawValue).tag(type)
+                    }
+                }
+                .pickerStyle(.segmented)
                 Button("Move to full") {
                     withAnimation(.interactiveSpring) {
                         panelState = .full
@@ -42,8 +47,26 @@ struct MainView: View {
                         Text("Switch to My layout")
                     }
                 }
+                Spacer()
+            }
+        }
+        .floatingPanel(
+            coordinator: MyPanelCoordinator.self
+        ) { proxy in
+            switch selectedContent {
+            case .list:
+                ContentView(proxy: proxy)
+            case .detail:
+                VStack {
+                    Text("off")
+                        .padding(.top, 32)
+                    Spacer()
+                }
             }
         }
+        .floatingPanelSurfaceAppearance(.transparent())
+        .floatingPanelLayout(panelLayout)
+        .floatingPanelState($panelState)
     }
 }
 

Sources/SwiftUI/FloatingPanelView.swift

@@ -110,7 +110,11 @@ struct FloatingPanelView<MainView: View, ContentView: View>: UIViewControllerRep
         _ uiViewController: UIHostingController<MainView>,
         context: Context
     ) {
+        uiViewController.rootView = main
+
+        context.coordinator.updateContent(content(context.coordinator.proxy))
         context.coordinator.onUpdate(context: context)
+
         applyEnvironment(context: context)
         applyAnimatableEnvironment(context: context)
     }
@@ -160,6 +164,9 @@ class FloatingPanelCoordinatorProxy {
 
     private var subscriptions: Set<AnyCancellable> = Set()
 
+    // Store a reference to the content hosting controller for dynamic updates
+    private weak var contentHostingController: UIViewController?
+
     var proxy: FloatingPanelProxy { origin.proxy }
     var controller: FloatingPanelController { origin.controller }
 
@@ -181,12 +188,25 @@ class FloatingPanelCoordinatorProxy {
         mainHostingController: UIHostingController<Main>,
         contentHostingController: UIHostingController<Content>
     ) {
+        // Store the content hosting controller reference
+        self.contentHostingController = contentHostingController
+
         origin.setupFloatingPanel(
             mainHostingController: mainHostingController,
             contentHostingController: contentHostingController
         )
     }
 
+    /// Updates the content of the floating panel with new content.
+    func updateContent<Content: View>(_ newContent: Content) {
+        guard
+            let hostingController = contentHostingController as? UIHostingController<Content>
+        else {
+            return
+        }
+        hostingController.rootView = newContent
+    }
+
     func onUpdate<Representable>(
         context: UIViewControllerRepresentableContext<Representable>
     ) where Representable: UIViewControllerRepresentable {