Implementing Bottom Sheets for Action-Driven Interfaces

Introduction

Bottom sheets are a fundamental UI pattern in Flutter for surfacing contextual actions without leaving the current screen. In mobile development, they allow you to present choices, controls, or transient workflows anchored to the bottom of the viewport. This tutorial shows when to use modal versus persistent bottom sheets, how to implement them in Flutter, and key design and accessibility considerations for action-driven interfaces.

When To Use Modal vs Persistent Bottom Sheets

Choose a modal bottom sheet when the user must make a single, focused decision or input that temporarily interrupts the current task—examples include action pickers, share sheets, or confirm dialogs. Modal sheets block interaction with the underlying screen and should be used for short, decisive tasks.

Use a persistent bottom sheet when you need continuous access to controls or contextual information while the user interacts with the rest of the UI—examples include media players, small inline toolbars, or filters. Persistent sheets remain visible and partially interactable alongside the primary content.

Building a Modal Bottom Sheet

In Flutter, showModalBottomSheet is the recommended API for modal sheets. Keep the sheet content concise and avoid deep navigation inside the sheet; if the action requires several steps, consider a full-screen dialog or a navigation-based flow. When building action lists, provide clear primary and secondary actions and visually emphasize the primary action.

Example: a compact action list with a primary confirm button.

showModalBottomSheet<void>(
  context: context,
  shape: RoundedRectangleBorder(borderRadius: BorderRadius.vertical(top: Radius.circular(16))),
  builder: (ctx) => Padding(
    padding: EdgeInsets.all(16),
    child: Column(mainAxisSize: MainAxisSize.min, children: [
      ListTile(title: Text('Delete item'), subtitle: Text('This action cannot be undone.')),
      Row(mainAxisAlignment: MainAxisAlignment.end, children: [
        TextButton(onPressed: () => Navigator.pop(ctx), child: Text('Cancel')),
        ElevatedButton(onPressed: () { /* confirm */ }, child: Text('Delete')),
      ])
    ]),
  ),
);

Creating a Persistent Bottom Sheet

Persistent bottom sheets attach to the scaffold and can be shown/hidden programmatically. Use them when you want ongoing controls that should not fully obscure content. Keep their height constrained and support drag-to-dismiss or expansion where appropriate. Resist packing them with complex navigation—keep persistent sheets lightweight.

Example: showing a persistent controller panel.

final controller = Scaffold.of(context).showBottomSheet<void>(
  (ctx) => Container(height: 120, padding: EdgeInsets.all(12), child: Text('Playback controls')),
);
// controller.close(); to dismiss

Styling choices matter: use rounded corners, subtle elevation, and clear separators. Ensure the sheet’s content scales and scrolls appropriately when the keyboard appears, and prefer SafeArea to avoid system UI overlap.

Accessibility and UX Considerations

Keyboard and Screen Reader Support: Ensure bottom sheets announce when they appear. For modal sheets, set canDismiss to true only when appropriate and provide explicit cancel actions. Use semantic labels for buttons and interactive elements so screen readers can describe the available actions.

Touch Targets and Gestures: Provide at least 48x48 logical pixels for touch targets. If you allow swipe-to-dismiss, ensure there is an accessible way to cancel or dismiss the sheet without relying purely on gestures.

Responsiveness and Orientation: On larger devices or landscape mode, consider using a wider, centered sheet or converting the flow into a dialog or side panel. In mobile development, screen size diversity requires adapting the sheet presentation: use full-screen dialogs for complex flows on small devices and partial sheets for quick actions.

Performance and Testing

Keep the sheet’s widget tree shallow—avoid embedding heavy builders or expensive computations directly in the sheet. Lazy-load expensive list items only when visible. Test animations and transitions on low-end devices to ensure the sheet appears smoothly without jank. For stateful interactions inside sheets, manage state with scoped providers or local State objects to prevent unnecessary rebuilds of the entire screen.

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Conclusion

Bottom sheets are a versatile, high-utility pattern for action-driven interfaces in Flutter. Use modal sheets for focused decisions and persistent sheets for ongoing controls. Prioritize clarity of actions, accessibility, and lightweight content to keep interactions fast and intuitive. With careful design and implementation, bottom sheets can greatly enhance task flow in mobile development without disrupting context or performance.