# Create an expandable FAB

> How to implement a FAB that expands to multiple buttons when tapped.



<?code-excerpt path-base="cookbook/effects/expandable_fab"?>

A Floating Action Button (FAB) is a round button that
floats near the bottom right of a content area.
This button represents the primary action for the
corresponding content, but sometimes, there is no primary action.
Instead, there are a few critical actions that the user might take.
In this case, you could create an expandable FAB like the one shown
in the following figure. When pressed, this expandable FAB spawns
multiple, other action buttons. Each button corresponds to one of
those critical actions.

The following animation shows the app's behavior:

![Expanding and collapsing the FAB](/assets/images/docs/cookbook/effects/ExpandingFAB.webp){:.site-mobile-screenshot}

## Create an ExpandableFab widget

Start by creating a new stateful widget called `ExpandableFab`.
This widget displays the primary FAB and coordinates the expansion
and collapse of the other action buttons. The widget takes
in parameters for whether or not the `ExpandedFab` begins in
the expanded position, what the maximum distance of each action button is,
and a list of children. You'll use the list later to provide
the other action buttons.

<?code-excerpt "lib/excerpt1.dart (ExpandableFab)"?>
```dart
@immutable
class ExpandableFab extends StatefulWidget {
  const ExpandableFab({
    super.key,
    this.initialOpen,
    required this.distance,
    required this.children,
  });

  final bool? initialOpen;
  final double distance;
  final List<Widget> children;

  @override
  State<ExpandableFab> createState() => _ExpandableFabState();
}

class _ExpandableFabState extends State<ExpandableFab> {
  @override
  Widget build(BuildContext context) {
    return const SizedBox();
  }
}
```

## FAB cross-fade

The `ExpandableFab` displays a blue edit button when collapsed
and a white close button when expanded. When expanding and collapsing,
these two buttons scale and fade between one another.

Implement the expand and collapse cross-fade between the two different FABs.

<?code-excerpt "lib/excerpt2.dart (ExpandableFabState)"?>
```dart
class _ExpandableFabState extends State<ExpandableFab> {
  bool _open = false;

  @override
  void initState() {
    super.initState();
    _open = widget.initialOpen ?? false;
  }

  void _toggle() {
    setState(() {
      _open = !_open;
    });
  }

  @override
  Widget build(BuildContext context) {
    return SizedBox.expand(
      child: Stack(
        alignment: Alignment.bottomRight,
        clipBehavior: Clip.none,
        children: [_buildTapToCloseFab(), _buildTapToOpenFab()],
      ),
    );
  }

  Widget _buildTapToCloseFab() {
    return SizedBox(
      width: 56,
      height: 56,
      child: Center(
        child: Material(
          shape: const CircleBorder(),
          clipBehavior: Clip.antiAlias,
          elevation: 4,
          child: InkWell(
            onTap: _toggle,
            child: Padding(
              padding: const EdgeInsets.all(8),
              child: Icon(Icons.close, color: Theme.of(context).primaryColor),
            ),
          ),
        ),
      ),
    );
  }

  Widget _buildTapToOpenFab() {
    return IgnorePointer(
      ignoring: _open,
      child: AnimatedContainer(
        transformAlignment: Alignment.center,
        transform: Matrix4.diagonal3Values(
          _open ? 0.7 : 1.0,
          _open ? 0.7 : 1.0,
          1.0,
        ),
        duration: const Duration(milliseconds: 250),
        curve: const Interval(0.0, 0.5, curve: Curves.easeOut),
        child: AnimatedOpacity(
          opacity: _open ? 0.0 : 1.0,
          curve: const Interval(0.25, 1.0, curve: Curves.easeInOut),
          duration: const Duration(milliseconds: 250),
          child: FloatingActionButton(
            onPressed: _toggle,
            child: const Icon(Icons.create),
          ),
        ),
      ),
    );
  }
}
```

The open button sits on top of the close button within a `Stack`,
allowing for the visual appearance of a cross-fade as the top button
appears and disappears.

To achieve the cross-fade animation, the open button uses an
`AnimatedContainer` with a scale transform and an `AnimatedOpacity`.
The open button scales down and fades out when the `ExpandableFab`
goes from collapsed to expanded. Then, the open button scales up
and fades in when the `ExpandableFab` goes from expanded to collapsed.

You'll notice that the open button is wrapped with an
`IgnorePointer` widget. This is because the open button always exists,
even when it's transparent. Without the `IgnorePointer`,
the open button always receives the tap event,
even when the close button is visible.

## Create an ActionButton widget

Each of the buttons that expand from the `ExpandableFab`
have the same design. They're  blue circles with white icons.
More precisely, the button background color is the `ColorScheme.secondary`
color, and the icon color is `ColorScheme.onSecondary`.

Define a new stateless widget called `ActionButton` to display
these round buttons.

<?code-excerpt "lib/main.dart (ActionButton)"?>
```dart
@immutable
class ActionButton extends StatelessWidget {
  const ActionButton({super.key, this.onPressed, required this.icon});

  final VoidCallback? onPressed;
  final Widget icon;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Material(
      shape: const CircleBorder(),
      clipBehavior: Clip.antiAlias,
      color: theme.colorScheme.secondary,
      elevation: 4,
      child: IconButton(
        onPressed: onPressed,
        icon: icon,
        color: theme.colorScheme.onSecondary,
      ),
    );
  }
}
```

Pass a few instances of this new `ActionButton` widget into your
`ExpandableFab`.

<?code-excerpt "lib/main.dart (FloatingActionButton)"?>
```dart
floatingActionButton: ExpandableFab(
  distance: 112,
  children: [
    ActionButton(
      onPressed: () => _showAction(context, 0),
      icon: const Icon(Icons.format_size),
    ),
    ActionButton(
      onPressed: () => _showAction(context, 1),
      icon: const Icon(Icons.insert_photo),
    ),
    ActionButton(
      onPressed: () => _showAction(context, 2),
      icon: const Icon(Icons.videocam),
    ),
  ],
),
```

## Expand and collapse the action buttons

The child `ActionButton`s should fly out from under the open
FAB when expanded. Then, the child `ActionButton`s should
fly back under the open FAB when collapsed.
This motion requires explicit (x,y) positioning of each
`ActionButton` and an `Animation` to choreograph changes to
those (x,y) positions over time.

Introduce an `AnimationController` and an `Animation` to
control the rate at which the various `ActionButton`s expand and collapse.

<?code-excerpt "lib/excerpt3.dart (ExpandableFabState3)" replace="/\/\/ code-excerpt-closing-bracket/}/g"?>
```dart
class _ExpandableFabState extends State<ExpandableFab>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller;
  late final Animation<double> _expandAnimation;
  bool _open = false;

  @override
  void initState() {
    super.initState();
    _open = widget.initialOpen ?? false;
    _controller = AnimationController(
      value: _open ? 1.0 : 0.0,
      duration: const Duration(milliseconds: 250),
      vsync: this,
    );
    _expandAnimation = CurvedAnimation(
      curve: Curves.fastOutSlowIn,
      reverseCurve: Curves.easeOutQuad,
      parent: _controller,
    );
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  void _toggle() {
    setState(() {
      _open = !_open;
      if (_open) {
        _controller.forward();
      } else {
        _controller.reverse();
      }
    });
  }
  }
```

Next, introduce a new stateless widget called `_ExpandingActionButton`,
and configure this widget to animate and position an individual `ActionButton`. The `ActionButton` is provided as a generic `Widget` called `child`.

<?code-excerpt "lib/excerpt3.dart (ExpandingActionButton)"?>
```dart
@immutable
class _ExpandingActionButton extends StatelessWidget {
  const _ExpandingActionButton({
    required this.directionInDegrees,
    required this.maxDistance,
    required this.progress,
    required this.child,
  });

  final double directionInDegrees;
  final double maxDistance;
  final Animation<double> progress;
  final Widget child;

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: progress,
      builder: (context, child) {
        final offset = Offset.fromDirection(
          directionInDegrees * (math.pi / 180.0),
          progress.value * maxDistance,
        );
        return Positioned(
          right: 4.0 + offset.dx,
          bottom: 4.0 + offset.dy,
          child: Transform.rotate(
            angle: (1.0 - progress.value) * math.pi / 2,
            child: child!,
          ),
        );
      },
      child: FadeTransition(opacity: progress, child: child),
    );
  }
}
```

The most important part of `_ExpandingActionButton` is the
`Positioned` widget, which positions the `child` at a specific (x,y)
coordinate within the surrounding `Stack`.
The `AnimatedBuilder` causes the `Positioned` widget to rebuild
every time the animation changes. The `FadeTransition` widget
orchestrates the appearance and disappearance of each
`ActionButton` as they expand and collapse, respectively.

:::note
The use of a `Positioned` widget within `_ExpandingActionButton`
implies that `_ExpandingActionButton` can only be used as a direct
child of a `Stack`. This is due to the explicit relationship
between `Positioned` and `Stack`.
:::

Finally, use the new `_ExpandingActionButton` widget
within the `ExpandableFab` to complete the exercise.

<?code-excerpt "lib/excerpt4.dart (ExpandableFabState4)" replace="/\/\/ code-excerpt-closing-bracket/}/g"?>
```dart
class _ExpandableFabState extends State<ExpandableFab>
    with SingleTickerProviderStateMixin {
  @override
  Widget build(BuildContext context) {
    return SizedBox.expand(
      child: Stack(
        alignment: Alignment.bottomRight,
        clipBehavior: Clip.none,
        children: [
          _buildTapToCloseFab(),
          ..._buildExpandingActionButtons(),
          _buildTapToOpenFab(),
        ],
      ),
    );
  }

  List<Widget> _buildExpandingActionButtons() {
    final children = <Widget>[];
    final count = widget.children.length;
    final step = 90.0 / (count - 1);
    for (
      var i = 0, angleInDegrees = 0.0;
      i < count;
      i++, angleInDegrees += step
    ) {
      children.add(
        _ExpandingActionButton(
          directionInDegrees: angleInDegrees,
          maxDistance: widget.distance,
          progress: _expandAnimation,
          child: widget.children[i],
        ),
      );
    }
    return children;
  }
  }
```

Congratulations! You now have an expandable FAB.

## Interactive example

Run the app:

* Click the FAB in the lower-right corner,
  represented with an Edit icon.
  It fans out to 3 buttons and is itself replaced by
  a close button, represented by an **X**.
* Click the close button to see the expanded
  buttons fly back to the original FAB and
  the **X** is replaced by the Edit icon.
* Expand the FAB again, and click on any
  of the 3 satellite buttons to see a dialog
  representing that button's action.


<!-- start dartpad -->

<?code-excerpt "lib/main.dart"?>
```dartpad title="Flutter expandable floating action button hands-on example in DartPad" run="true"
import 'dart:math' as math;

import 'package:flutter/material.dart';

void main() {
  runApp(
    const MaterialApp(
      home: ExampleExpandableFab(),
      debugShowCheckedModeBanner: false,
    ),
  );
}

@immutable
class ExampleExpandableFab extends StatelessWidget {
  static const _actionTitles = ['Create Post', 'Upload Photo', 'Upload Video'];

  const ExampleExpandableFab({super.key});

  void _showAction(BuildContext context, int index) {
    showDialog<void>(
      context: context,
      builder: (context) {
        return AlertDialog(
          content: Text(_actionTitles[index]),
          actions: [
            TextButton(
              onPressed: () => Navigator.of(context).pop(),
              child: const Text('CLOSE'),
            ),
          ],
        );
      },
    );
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Expandable Fab')),
      body: ListView.builder(
        padding: const EdgeInsets.symmetric(vertical: 8),
        itemCount: 25,
        itemBuilder: (context, index) {
          return FakeItem(isBig: index.isOdd);
        },
      ),
      floatingActionButton: ExpandableFab(
        distance: 112,
        children: [
          ActionButton(
            onPressed: () => _showAction(context, 0),
            icon: const Icon(Icons.format_size),
          ),
          ActionButton(
            onPressed: () => _showAction(context, 1),
            icon: const Icon(Icons.insert_photo),
          ),
          ActionButton(
            onPressed: () => _showAction(context, 2),
            icon: const Icon(Icons.videocam),
          ),
        ],
      ),
    );
  }
}

@immutable
class ExpandableFab extends StatefulWidget {
  const ExpandableFab({
    super.key,
    this.initialOpen,
    required this.distance,
    required this.children,
  });

  final bool? initialOpen;
  final double distance;
  final List<Widget> children;

  @override
  State<ExpandableFab> createState() => _ExpandableFabState();
}

class _ExpandableFabState extends State<ExpandableFab>
    with SingleTickerProviderStateMixin {
  late final AnimationController _controller;
  late final Animation<double> _expandAnimation;
  bool _open = false;

  @override
  void initState() {
    super.initState();
    _open = widget.initialOpen ?? false;
    _controller = AnimationController(
      value: _open ? 1.0 : 0.0,
      duration: const Duration(milliseconds: 250),
      vsync: this,
    );
    _expandAnimation = CurvedAnimation(
      curve: Curves.fastOutSlowIn,
      reverseCurve: Curves.easeOutQuad,
      parent: _controller,
    );
  }

  @override
  void dispose() {
    _controller.dispose();
    super.dispose();
  }

  void _toggle() {
    setState(() {
      _open = !_open;
      if (_open) {
        _controller.forward();
      } else {
        _controller.reverse();
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return SizedBox.expand(
      child: Stack(
        alignment: Alignment.bottomRight,
        clipBehavior: Clip.none,
        children: [
          _buildTapToCloseFab(),
          ..._buildExpandingActionButtons(),
          _buildTapToOpenFab(),
        ],
      ),
    );
  }

  Widget _buildTapToCloseFab() {
    return SizedBox(
      width: 56,
      height: 56,
      child: Center(
        child: Material(
          shape: const CircleBorder(),
          clipBehavior: Clip.antiAlias,
          elevation: 4,
          child: InkWell(
            onTap: _toggle,
            child: Padding(
              padding: const EdgeInsets.all(8),
              child: Icon(Icons.close, color: Theme.of(context).primaryColor),
            ),
          ),
        ),
      ),
    );
  }

  List<Widget> _buildExpandingActionButtons() {
    final children = <Widget>[];
    final count = widget.children.length;
    final step = 90.0 / (count - 1);
    for (
      var i = 0, angleInDegrees = 0.0;
      i < count;
      i++, angleInDegrees += step
    ) {
      children.add(
        _ExpandingActionButton(
          directionInDegrees: angleInDegrees,
          maxDistance: widget.distance,
          progress: _expandAnimation,
          child: widget.children[i],
        ),
      );
    }
    return children;
  }

  Widget _buildTapToOpenFab() {
    return IgnorePointer(
      ignoring: _open,
      child: AnimatedContainer(
        transformAlignment: Alignment.center,
        transform: Matrix4.diagonal3Values(
          _open ? 0.7 : 1.0,
          _open ? 0.7 : 1.0,
          1.0,
        ),
        duration: const Duration(milliseconds: 250),
        curve: const Interval(0.0, 0.5, curve: Curves.easeOut),
        child: AnimatedOpacity(
          opacity: _open ? 0.0 : 1.0,
          curve: const Interval(0.25, 1.0, curve: Curves.easeInOut),
          duration: const Duration(milliseconds: 250),
          child: FloatingActionButton(
            onPressed: _toggle,
            child: const Icon(Icons.create),
          ),
        ),
      ),
    );
  }
}

@immutable
class _ExpandingActionButton extends StatelessWidget {
  const _ExpandingActionButton({
    required this.directionInDegrees,
    required this.maxDistance,
    required this.progress,
    required this.child,
  });

  final double directionInDegrees;
  final double maxDistance;
  final Animation<double> progress;
  final Widget child;

  @override
  Widget build(BuildContext context) {
    return AnimatedBuilder(
      animation: progress,
      builder: (context, child) {
        final offset = Offset.fromDirection(
          directionInDegrees * (math.pi / 180.0),
          progress.value * maxDistance,
        );
        return Positioned(
          right: 4.0 + offset.dx,
          bottom: 4.0 + offset.dy,
          child: Transform.rotate(
            angle: (1.0 - progress.value) * math.pi / 2,
            child: child!,
          ),
        );
      },
      child: FadeTransition(opacity: progress, child: child),
    );
  }
}

@immutable
class ActionButton extends StatelessWidget {
  const ActionButton({super.key, this.onPressed, required this.icon});

  final VoidCallback? onPressed;
  final Widget icon;

  @override
  Widget build(BuildContext context) {
    final theme = Theme.of(context);
    return Material(
      shape: const CircleBorder(),
      clipBehavior: Clip.antiAlias,
      color: theme.colorScheme.secondary,
      elevation: 4,
      child: IconButton(
        onPressed: onPressed,
        icon: icon,
        color: theme.colorScheme.onSecondary,
      ),
    );
  }
}

@immutable
class FakeItem extends StatelessWidget {
  const FakeItem({super.key, required this.isBig});

  final bool isBig;

  @override
  Widget build(BuildContext context) {
    return Container(
      margin: const EdgeInsets.symmetric(vertical: 8, horizontal: 24),
      height: isBig ? 128 : 36,
      decoration: BoxDecoration(
        borderRadius: const BorderRadius.all(Radius.circular(8)),
        color: Colors.grey.shade300,
      ),
    );
  }
}
```