[xxxOVALxxx]

This PR is stacked on top of #12515
Please review #12515 first

This PR adds native iOS-style rubber-banding resistance to CupertinoSheetRoute / showCupertinoSheet when dragging is disabled (enableDrag: false)

Flutter on the left, SwiftUI on the right

output.mp4

Flutter example

import 'package:cupertino_ui/cupertino_ui.dart';

void main() {
  runApp(const CupertinoSheetDemoApp());
}

class CupertinoSheetDemoApp extends StatelessWidget {
  const CupertinoSheetDemoApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const CupertinoApp(
      theme: CupertinoThemeData(
        brightness: Brightness.light,
        primaryColor: CupertinoColors.systemBlue,
      ),
      home: ContentView(),
    );
  }
}

class ContentView extends StatelessWidget {
  const ContentView({super.key});

  void _openStandardSheet(BuildContext context) {
    showCupertinoSheet<void>(
      context: context,
      showDragHandle: true,
      enableDrag: true,
      scrollableBuilder:
          (BuildContext context, ScrollController scrollController) {
            return const StandardSheetView();
          },
    );
  }

  void _openNonDismissibleListSheet(BuildContext context) {
    showCupertinoSheet<void>(
      context: context,
      showDragHandle: false,
      enableDrag: false,
      scrollableBuilder:
          (BuildContext context, ScrollController scrollController) {
            return NonDismissibleListSheetView(
              scrollController: scrollController,
            );
          },
    );
  }

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      navigationBar: const CupertinoNavigationBar(
        middle: Text('Cupertino Sheet Demo'),
      ),
      child: SafeArea(
        child: Padding(
          padding: const EdgeInsets.symmetric(horizontal: 20.0),
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              SizedBox(
                width: double.infinity,
                child: CupertinoButton.filled(
                  borderRadius: BorderRadius.circular(12.0),
                  padding: const EdgeInsets.symmetric(vertical: 16.0),
                  onPressed: () => _openStandardSheet(context),
                  child: const Text(
                    '1. Open Standard Sheet',
                    style: TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
                  ),
                ),
              ),
              const SizedBox(height: 20),
              SizedBox(
                width: double.infinity,
                child: CupertinoButton.filled(
                  borderRadius: BorderRadius.circular(12.0),
                  padding: const EdgeInsets.symmetric(vertical: 16.0),
                  onPressed: () => _openNonDismissibleListSheet(context),
                  child: const Text(
                    '2. Open Sheet with List',
                    textAlign: TextAlign.center,
                    style: TextStyle(fontSize: 17, fontWeight: FontWeight.w600),
                  ),
                ),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

class StandardSheetView extends StatelessWidget {
  const StandardSheetView({super.key});

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      navigationBar: CupertinoNavigationBar(
        middle: const Text('Standard Sheet'),
        leading: CupertinoButton(
          padding: EdgeInsets.zero,
          onPressed: () => Navigator.of(context).pop(),
          child: const Text('Close'),
        ),
      ),
      child: SafeArea(
        child: Center(
          child: Padding(
            padding: const EdgeInsets.all(24.0),
            child: Column(
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                const Icon(
                  CupertinoIcons.arrow_down_circle,
                  size: 64,
                  color: CupertinoColors.systemBlue,
                ),
                const SizedBox(height: 16),
                const Text(
                  'Standard Dismissible Sheet',
                  style: TextStyle(fontSize: 20, fontWeight: FontWeight.bold),
                  textAlign: TextAlign.center,
                ),
                const SizedBox(height: 8),
                Text(
                  'Swipe down on the sheet to dismiss it.',
                  style: TextStyle(
                    fontSize: 15,
                    color: CupertinoColors.secondaryLabel.resolveFrom(context),
                  ),
                  textAlign: TextAlign.center,
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

class NonDismissibleListSheetView extends StatelessWidget {
  const NonDismissibleListSheetView({
    super.key,
    required this.scrollController,
  });

  final ScrollController scrollController;

  @override
  Widget build(BuildContext context) {
    return CupertinoPageScaffold(
      backgroundColor: CupertinoColors.systemGroupedBackground,
      navigationBar: CupertinoNavigationBar(
        middle: const Text('enableDrag: false'),
        trailing: CupertinoButton(
          padding: EdgeInsets.zero,
          onPressed: () => Navigator.of(context).pop(),
          child: const Text(
            'Done',
            style: TextStyle(fontWeight: FontWeight.bold),
          ),
        ),
      ),
      child: SafeArea(
        bottom: false,
        child: ListView(
          controller: scrollController,
          physics: const AlwaysScrollableScrollPhysics(),
          children: <Widget>[
            CupertinoListSection.insetGrouped(
              hasLeading: false,
              children: List.generate(30, (int index) {
                final int itemIndex = index + 1;
                return CupertinoListTile(
                  title: Text('Item $itemIndex'),
                  subtitle: Text(
                    'Subtitle for item $itemIndex',
                    style: TextStyle(
                      color: CupertinoColors.secondaryLabel.resolveFrom(
                        context,
                      ),
                      fontSize: 13,
                    ),
                  ),
                  trailing: const CupertinoListTileChevron(),
                  onTap: () {},
                );
              }),
            ),
          ],
        ),
      ),
    );
  }
}

SwiftUI example

import SwiftUI

struct ContentView: View {
    @State private var isStandardSheetPresented = false
    @State private var isNonDismissibleSheetPresented = false

    var body: some View {
        NavigationStack {
            VStack(spacing: 20) {
                Button {
                    isStandardSheetPresented = true
                } label: {
                    Text("1. Open Standard Sheet")
                        .frame(maxWidth: .infinity)
                }
                .buttonStyle(.borderedProminent)
                .controlSize(.large)

                Button {
                    isNonDismissibleSheetPresented = true
                } label: {
                    Text("2. Open Sheet with List")
                        .multilineTextAlignment(.center)
                        .frame(maxWidth: .infinity)
                }
                .buttonStyle(.borderedProminent)
                .controlSize(.large)
            }
            .padding(.horizontal, 20)
            .navigationTitle("Cupertino Sheet Demo")
            .navigationBarTitleDisplayMode(.inline)
            .sheet(isPresented: $isStandardSheetPresented) {
                StandardSheetView()
            }
            .sheet(isPresented: $isNonDismissibleSheetPresented) {
                NonDismissibleListSheetView()
            }
        }
    }
}

struct StandardSheetView: View {
    @Environment(\.dismiss) private var dismiss

    var body: some View {
        NavigationStack {
            VStack(spacing: 16) {
                Image(systemName: "arrow.down.circle")
                    .font(.system(size: 64))
                    .foregroundStyle(.blue)

                Text("Standard Dismissible Sheet")
                    .font(.title3)
                    .fontWeight(.bold)

                Text("Swipe down on the sheet to dismiss it.")
                    .font(.subheadline)
                    .foregroundStyle(.secondary)
                    .multilineTextAlignment(.center)
            }
            .padding(24)
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            .navigationTitle("Standard Sheet")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .cancellationAction) {
                    Button("Close") {
                        dismiss()
                    }
                }
            }
        }
        .presentationDragIndicator(.visible)
    }
}

struct NonDismissibleListSheetView: View {
    @Environment(\.dismiss) private var dismiss

    var body: some View {
        NavigationStack {
            List {

                ForEach(1...30, id: \.self) { index in
                    HStack {
                        VStack(alignment: .leading, spacing: 2) {
                            Text("Item \(index)")
                                .font(.body)
                            Text("Subtitle for item \(index)")
                                .font(.footnote)
                                .foregroundStyle(.secondary)
                        }
                        Spacer()
                        Image(systemName: "chevron.right")
                            .font(.footnote)
                            .fontWeight(.semibold)
                            .foregroundStyle(.tertiary)
                    }
                    .contentShape(Rectangle())
                    .onTapGesture {
                    }
                }
            }
            .navigationTitle("enableDrag: false")
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .confirmationAction) {
                    Button("Done") {
                        dismiss()
                    }
                    .fontWeight(.bold)
                }
            }
        }
        .presentationDragIndicator(.hidden)
        .interactiveDismissDisabled(true)
    }
}

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the AI contribution guidelines and understand my responsibilities, or I am not using AI tools.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets, e.g. [shared_preferences]
• I linked to at least one issue that this PR fixes in the description above.
• I followed the version and CHANGELOG instructions, using semantic versioning and the repository CHANGELOG style, or I have commented below to indicate which documented exception this PR falls under¹.
• I updated/added any relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or I have commented below to indicate which test exemption this PR falls under¹.
• All existing and new tests are passing.

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Footnotes

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[gemini-code-assist]

Code Review

This pull request implements a rubber-banding and spring-back animation for Cupertino sheets when dragging is disabled, using Apple's rubber-banding formula and a physical spring simulation. It also ensures that sheets ignore gestures mid-dismissal. Feedback suggests declaring the global _sheetSpring variable as final, optimizing the squaring calculation in _computeRubberBandFriction by replacing math.pow with direct multiplication, and checking navigator.mounted before calling navigator.didStopUserGesture() to prevent potential exceptions during the animation.

[xxxOVALxxx]

I'm trying to fix an issue where, when passing the scrollableBuilder parameter, if the user drags the sheet and tries to intercept it on the fly, scrolling stops working.

To reproduce this, take the penultimate commit and replace line 813 with:
enabledCallback: () => !(controller?.isAnimating ?? false) || popGestureInProgress,
and line 950 with:
enabledCallback: () => !(route.controller?.isAnimating ?? false) || route.popGestureInProgress,

When re-intercepting the sheet on the fly, the hit test/arena for some reason doesn’t include the Scrollable’s own internal VerticalDragGestureRecognizer (it’s simply missing from the participants in Gesture arena 13), which causes all vertical drag events to be handled exclusively by the external _CupertinoDragGestureDetector, which can only move the sheet itself and is unaware of applyUserOffset or content scrolling.

debugPrintGestureArenaDiagnostics logs

flutter: Gesture arena 12   ❙ ★ Opening new gesture arena.
flutter: Gesture arena 12   ❙ Adding: TapGestureRecognizer#54dda(debugOwner: GestureDetector, state: ready, button: 1)
flutter: Gesture arena 12   ❙ Adding: VerticalDragGestureRecognizer#56f4f(start behavior: start)
flutter: Gesture arena 12   ❙ Adding: VerticalDragGestureRecognizer#80273(debugOwner: _CupertinoDragGestureDetectorState<void>#1307c, start behavior: start)
flutter: Gesture arena 12   ❙ Closing with 3 members.
flutter: Gesture arena 12   ❙ Rejecting: TapGestureRecognizer#54dda(debugOwner: GestureDetector, state: possible, button: 1)
flutter: Gesture arena 12   ❙ Accepting: VerticalDragGestureRecognizer#56f4f(start behavior: start)
flutter: Gesture arena 12   ❙ Self-declared winner: VerticalDragGestureRecognizer#56f4f(start behavior: start)
flutter: Gesture arena 13   ❙ ★ Opening new gesture arena.
flutter: Gesture arena 13   ❙ Adding: VerticalDragGestureRecognizer#80273(debugOwner: _CupertinoDragGestureDetectorState<void>#1307c, start behavior: start)
flutter: Gesture arena 13   ❙ Adding: _AnyTapGestureRecognizer#e041b(state: ready, button: 1)
flutter: Gesture arena 13   ❙ Closing with 2 members.
flutter: Gesture arena 13   ❙ Accepting: VerticalDragGestureRecognizer#80273(debugOwner: _CupertinoDragGestureDetectorState<void>#1307c, start behavior: start)
flutter: Gesture arena 13   ❙ Self-declared winner: VerticalDragGestureRecognizer#80273(debugOwner: _CupertinoDragGestureDetectorState<void>#1307c, start behavior: start)

Screen.Recording.2026-09-12.at.11.46.14.mov

I committed my latest progress in the most recent commit, which fixes the problem but introduces a new regression in behavior when the entire sheet becomes a scrollable area.

Screen.Recording.2026-09-12.at.11.04.19.mov

I’m not sure if it’s possible to solve this problem without reworking the widget’s architecture.