Flutter BottomAppBar Tutorial with Examples

BottomAppBar
child
shape
color
clipBehavior

1. BottomAppBar

A bottom menu is a traditional style of iOS apps. In Flutter, you can do this with BottomAppBar. Besides, the BottomAppBar also has a handy feature that allows you to attach a FloatingActionButton to it.

BottomAppBar Constructor:

BottomAppBar constructor

const BottomAppBar(
    {Key key,
    Color color,
    double elevation,
    NotchedShape shape,
    Clip clipBehavior: Clip.none,
    double notchMargin: 4.0,
    Widget child}
)

The BottomAppBar is usually placed in a Scaffold through the AppBar.bottomNavigationBar property, and it will appear at the bottom of the Scaffold.

Flutter BottomNavigationBar

2. child

child is the most important property of the BottomAppBar. In most use cases, it will be a Row, and this Row object contains one or more child Widget(s)such as IconButton, PopupMenuButton,etc.

Widget child

An example of a BottomAppBar whose action(s) are IconButton(s) and PopupMenuButton(s).

main.dart (child - ex1)

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Title of Application',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("BottomAppBar Example"),
        ),
        body: Center(
            child:  Text(
              'Flutter BottomAppBar Example',
            )
        ),
        bottomNavigationBar: BottomAppBar(
          child: new Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.start,
            children: <Widget>[
              IconButton(icon: Icon(Icons.home), onPressed: () {},),
              PopupMenuButton(
                icon: Icon(Icons.share),
                itemBuilder: (context) => [
                  PopupMenuItem(
                    value: 1,
                    child: Text("Facebook"),
                  ),
                  PopupMenuItem(
                    value: 2,
                    child: Text("Instagram"),
                  ),
                ],
              ),
              IconButton(icon: Icon(Icons.email), onPressed: () {},),
            ],
          ),
        )
    );
  }
}

To extend the example above, we attach a FloatingActionButton to the right side of the BottomAppBar.

main.dart (child ex2)

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Title of Application',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("BottomAppBar Example"),
        ),
        body: Center(
            child:  Text(
              'Flutter BottomAppBar Example',
            )
        ),
        floatingActionButton: FloatingActionButton.extended (
          elevation: 4.0,
          icon: const Icon(Icons.add),
          label: const Text('Add a task'),
          onPressed: () {},
        ),
        floatingActionButtonLocation: FloatingActionButtonLocation.endDocked,
        bottomNavigationBar: BottomAppBar(
          child: new Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.start,
            children: <Widget>[
              IconButton(icon: Icon(Icons.home), onPressed: () {},),
              PopupMenuButton(
                icon: Icon(Icons.share),
                itemBuilder: (context) => [
                  PopupMenuItem(
                    value: 1,
                    child: Text("Facebook"),
                  ),
                  PopupMenuItem(
                    value: 2,
                    child: Text("Instagram"),
                  ),
                ],
              ),
              IconButton(icon: Icon(Icons.email), onPressed: () {},),
            ],
          ),
        )
    );
  }
}

For example: A BottomAppBar along with a FloatingActionButton is anchored in the middle.

main.dart (child ex3)

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Title of Application',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("BottomAppBar Example"),
        ),
        body: Center(
            child:  Text(
              'Flutter BottomAppBar Example',
            )
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () { },
          tooltip: 'Increment',
          child: Icon(Icons.add),
          elevation: 2.0,
        ),
        floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
        bottomNavigationBar: BottomAppBar(
          child: new Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              IconButton(icon: Icon(Icons.menu), onPressed: () {},),
              IconButton(icon: Icon(Icons.search), onPressed: () {},),
            ],
          ),
        )
    );
  }
}

Example: Customize the height of the BottomAppBar:

main.dart (child ex4)

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Title of Application',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("BottomAppBar Example"),
        ),
        body: Center(
            child:  Text(
              'Flutter BottomAppBar Example',
            )
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () { },
          tooltip: 'Increment',
          child: Icon(Icons.add),
          elevation: 2.0,
        ),
        floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
        bottomNavigationBar: BottomAppBar(
          child: Container(
            height: 90.0,
            child: new Row(
              mainAxisSize: MainAxisSize.max,
              mainAxisAlignment: MainAxisAlignment.spaceBetween,
              children: <Widget>[
                IconButton(icon: Icon(Icons.menu), onPressed: () {},),
                IconButton(icon: Icon(Icons.settings), onPressed: () {},),
                IconButton(icon: Icon(Icons.search), onPressed: () {},),
              ],
            ),
          )
        )
    );
  }
}

3. shape

shape property is used to define the shape of the notch when the FloatingActionButton is placed on a BottomAppBar.

NotchedShape shape

NotchedShape is an abstract class, it has two subclasses CircularNotchedRectangle and AutomaticNotchedShape.

The CircularNotchedRectangle class helps you create a circular notch that fit the circular FloatingActionButton(s).
The AutomaticNotchedShape class helps you create custom notches that fit the different shapes of the FloatingActionButton.

CircularNotchedRectangle
AutomaticNotchedShape

Now take a look at an example of using CircularNotchedRectangle to create a circular notch:

main.dart (shape ex1)

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Title of Application',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("BottomAppBar Example"),
        ),
        body: Center(
            child:  Text(
              'Flutter BottomAppBar Example',
            )
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () { },
          tooltip: 'Increment',
          child: Icon(Icons.add),
          elevation: 2.0,
        ),
        floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              IconButton(icon: Icon(Icons.menu), onPressed: () {},),
              IconButton(icon: Icon(Icons.search), onPressed: () {},),
            ],
          ),
          shape: CircularNotchedRectangle(),
        )
    );
  }
}

Note: Do not use the CircularNotchedRectangle with a FloatingActionButton which is not a circle. Otherwise, you will get a unsatisfactory result:

For example, use an AutomaticNotchedShape with a rectangular FloatingActionButton:

main.dart (shape ex3)

import 'package:flutter/material.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Title of Application',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text("BottomAppBar Example"),
        ),
        body: Center(
            child:  Text(
              'Flutter BottomAppBar Example',
            )
        ),
        floatingActionButton: FloatingActionButton.extended (
          elevation: 4.0,
          icon: const Icon(Icons.add),
          label: const Text('Add a task'),
          onPressed: () {},
        ),
        floatingActionButtonLocation: FloatingActionButtonLocation.centerDocked,
        bottomNavigationBar: BottomAppBar(
          child: Row(
            mainAxisSize: MainAxisSize.max,
            mainAxisAlignment: MainAxisAlignment.spaceBetween,
            children: <Widget>[
              IconButton(icon: Icon(Icons.menu), onPressed: () {},),
              IconButton(icon: Icon(Icons.search), onPressed: () {},),
            ],
          ),
          shape: AutomaticNotchedShape(
              RoundedRectangleBorder(),
              StadiumBorder(side: BorderSide())
          ),
        )
    );
  }
}

4. color

The color property is used to specify the color of BottomAppBar.

Color color

color (ex1)

BottomAppBar(
  child: Row(
    mainAxisSize: MainAxisSize.max,
    mainAxisAlignment: MainAxisAlignment.spaceBetween,
    children: <Widget>[
      IconButton(icon: Icon(Icons.menu), onPressed: () {},),
      IconButton(icon: Icon(Icons.search), onPressed: () {},),
    ],
  ),
  shape: CircularNotchedRectangle(),
  color: Colors.greenAccent
)

5. clipBehavior

Clip clipBehavior: Clip.none

Flutter Clipping