Flutter BottomNavigationBar Tutorial with Examples

BottomNavigationBar
Example
items
onTap
currentIndex
type
iconSize
selectedIconTheme
unselectedIconTheme
selectedLabelStyle
unselectedLabelStyle
showSelectedLabels
showUnselectedLabels
selectedFontSize
unselectedFontSize
backgroundColor
selectedItemColor
unselectedItemColor
fixedColor
mouseCursor

1. BottomNavigationBar

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

BottomNavigationBar Constructor:

BottomNavigationBar Constructor

BottomNavigationBar(
    {Key key,
    @required List<BottomNavigationBarItem> items,
    ValueChanged<int> onTap,
    int currentIndex: 0,
    double elevation,
    BottomNavigationBarType type,
    Color fixedColor,
    Color backgroundColor,
    double iconSize: 24.0,
    Color selectedItemColor,
    Color unselectedItemColor,
    IconThemeData selectedIconTheme,
    IconThemeData unselectedIconTheme,
    double selectedFontSize: 14.0,
    double unselectedFontSize: 12.0,
    TextStyle selectedLabelStyle,
    TextStyle unselectedLabelStyle,
    bool showSelectedLabels: true,
    bool showUnselectedLabels,
    MouseCursor mouseCursor}
)

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

BottomNavigationBar is pretty similar to the BottomAppBar in terms of usage. The BottomNavigationBar offers a template for a navigation bar, so it is simple and easy to use. However, if you want to unleash your creativity, use the BottomAppBar.

Flutter BottomAppBar

2. Example

Let's get started with a complete example of the BottomNavigationBar. It will help you understand how this Widget works.

main.dart (ex1)

import 'package:flutter/material.dart';

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

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

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

  @override
  State<StatefulWidget> createState() {
    return MyHomePageState();
  }

}

class MyHomePageState extends State<MyHomePage> {
  int selectedIndex = 0;
  Widget _myContacts = MyContacts();
  Widget _myEmails = MyEmails();
  Widget _myProfile = MyProfile();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("BottomNavigationBar Example"),
      ),
      body:  this.getBody(),
      bottomNavigationBar: BottomNavigationBar(
        type: BottomNavigationBarType.fixed,
        currentIndex: this.selectedIndex,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.contacts),
            title: Text("Contacts"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.mail),
            title: Text("Emails"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            title: Text("Profile"),
          )
        ],
        onTap: (int index) {
          this.onTapHandler(index);
        },
      ),
    );
  }

  Widget getBody( )  {
    if(this.selectedIndex == 0) {
      return this._myContacts;
    } else if(this.selectedIndex==1) {
      return this._myEmails;
    } else {
      return this._myProfile;
    }
  }

  void onTapHandler(int index)  {
    this.setState(() {
      this.selectedIndex = index;
    });
  }
}

class MyContacts extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(child: Text("Contacts"));
  }
}

class MyEmails extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(child: Text("Emails"));
  }
}

class MyProfile extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Center(child: Text("Profile"));
  }
}

3. items

items property is used to define the list of the BottomNavigationBar items. This property is required and the number of items must be greater than or equal to 2, otherwise you will get an error.

@required List<BottomNavigationBarItem> items

BottomNavigationBarItem Constructor:

BottomNavigationBarItem Constructor

const BottomNavigationBarItem(
    {@required Widget icon,
    Widget title,
    Widget activeIcon,
    Color backgroundColor}
)

For example:

main.dart (items 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("BottomNavigationBar Example"),
      ),
      body: Center(
          child:  Text(
            'Flutter BottomNavigationBar Example',
          )
      ),
      bottomNavigationBar: BottomNavigationBar(
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.home),
            title: Text("Home"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.mail),
            title: Text("Messages"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            title: Text("Profile"),
          )
        ],
      ),
    );
  }
}

4. onTap

onTap is a callback function. It will be called when the user taps on an item of the BottomNavigationBar.

ValueChanged<int> onTap

main.dart (onTab ex1)

import 'package:flutter/material.dart';

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

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

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

  @override
  State<StatefulWidget> createState() {
    return MyHomePageState();
  }

}

class MyHomePageState extends State<MyHomePage> {
  int tapCount = 0;
  int selectedIndex = 0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("BottomNavigationBar Example"),
      ),
      body: Center(
          child: Text("Tap Count: " + this.tapCount.toString()
                       + ", Index: " + this.selectedIndex.toString())
      ),
      bottomNavigationBar: BottomNavigationBar(
        currentIndex: this.selectedIndex,
        items: [
          BottomNavigationBarItem(
            icon: Icon(Icons.contacts),
            title: Text("Contacts"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.mail),
            title: Text("Emails"),
          ),
          BottomNavigationBarItem(
            icon: Icon(Icons.person),
            title: Text("Profile"),
          )
        ],
        onTap: (int index) {
          this.onTapHandler(index);
        },
      ),
    );
  }

  void onTapHandler(int index)  {
    this.setState(() {
      this.tapCount++;
      this.selectedIndex = index;
    });
  }
}

5. currentIndex

currentIndex is the index of the BottomNavigationBar item currently selected. Its default value is 0 corresponding to the first item.

int currentIndex: 0

6. type

BottomNavigationBarType type

7. iconSize

iconSize property is used to specify the size of the icon of all the BottomNavigationBarItem(s).

double iconSize: 24.0

iconSize (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  iconSize: 48,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
),

8. selectedIconTheme

selectedIconTheme property is used to set the size, color, and opacity for selected BottomNavigationBarItem icon.

IconThemeData selectedIconTheme

IconThemeData Constructor

const IconThemeData (
    {Color color,
    double opacity,
    double size}
)

If the selectedIconTheme property is used, you should specify a value for the unselectedIconTheme property. Otherwise, you will not see icons on the unselected BottomNavigationBarItem(s).

selectedIconTheme (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedIconTheme: IconThemeData (
      color: Colors.red,
      opacity: 1.0,
      size: 30
  ),
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

9. unselectedIconTheme

The unselectedIconTheme property is used to set the size, color, and opacity for the icon of the unselected BottomNavigationBarItem(s).

IconThemeData unselectedIconTheme

IconThemeData constructor

const IconThemeData (
    {Color color,
    double opacity,
    double size}
)

If the unselectedIconTheme property is used, you should specify a value for the selectedIconTheme property. If not, you will not see the icon on the selected BottomNavigationBarItem.

unselectedIconTheme (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedIconTheme: IconThemeData (
      color: Colors.red,
      opacity: 1.0,
      size: 45
  ),
  unselectedIconTheme: IconThemeData (
      color: Colors.black45,
      opacity: 0.5,
      size: 25
  ),
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
),

10. selectedLabelStyle

selectedLabelStyle property is used to specify the text style on the label of the selected BottomNavigationBarItem.

TextStyle selectedLabelStyle

selectedLabelStyle (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedLabelStyle: TextStyle(fontWeight: FontWeight.bold, fontSize: 22),
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

11. unselectedLabelStyle

unselectedLabelStyle property is used to specify the text style on the label of the unselected BottomNavigationBarItem(s).

TextStyle unselectedLabelStyle

unselectedLabelStyle (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedLabelStyle: TextStyle(fontWeight: FontWeight.bold, fontSize: 22),
  unselectedLabelStyle: TextStyle(fontStyle: FontStyle.italic),
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

12. showSelectedLabels

showSelectedLabels property is used to allow or disallow labels to be displayed on the currently selected BottomNavigationBarItem. Its default value is true.

bool showSelectedLabels: true

showSelectedLabels (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  showSelectedLabels: false,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

13. showUnselectedLabels

showUnselectedLabels property is used to allow or disallow labels to be displayed on the unselected BottomNavigationBarItem. Its default value is true.

bool showUnselectedLabels

showUnselectedLabels (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  showUnselectedLabels: false,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

14. selectedFontSize

selectedFontSize property is used to specify the font size on the selected BottomNavigationBarItem. Its default value is 14.

double selectedFontSize: 14.0

selectedFontSize (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedFontSize: 20,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

15. unselectedFontSize

selectedFontSize property is used to specify the font size on the unselected BottomNavigationBarItem. Its default value is 12.

double unselectedFontSize: 12.0

unselectedFontSize (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedFontSize: 20,
  unselectedFontSize: 15,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

16. backgroundColor

backgroundColor property is used to specify the background color of the BottomNavigationBar.

Color backgroundColor

backgroundColor (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  backgroundColor : Colors.greenAccent,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

17. selectedItemColor

selectedItemColor property is used to specify the color of the selected BottomNavigationBarItem, which works for the icon and label.

Note: selectedItemColor property is the same as fixedColor, which you are only allowed to use one of these two properties.

Color selectedItemColor

selectedItemColor (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedItemColor : Colors.red,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

18. unselectedItemColor

unselectedItemColor property is used to specify the color of the unselected BottomNavigationBarItem, which works for the icon and label.

Color unselectedItemColor

unselectedItemColor (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  selectedItemColor : Colors.red,
  unselectedItemColor: Colors.cyan,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

19. fixedColor

The fixedColor property is similar to the selectedItemColor property. Both are used to specify the color of the selected BottomNavigationBarItem. It works for the icon and label.

Note: fixedColor is an old name which is still available for the purpose of backwards compatibility. You should use the selectedItemColor property and not allowed to use both at the same time.

Color fixedColor

fixedColor (ex1)

BottomNavigationBar(
  currentIndex: this.selectedIndex,
  fixedColor: Colors.red,
  items: [
    BottomNavigationBarItem(
      icon: Icon(Icons.contacts),
      title: Text("Contacts"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.mail),
      title: Text("Emails"),
    ),
    BottomNavigationBarItem(
      icon: Icon(Icons.person),
      title: Text("Profile"),
    )
  ],
  onTap: (int index) {
    this.setState(() {
      this.selectedIndex = index;
    });
  },
)

20. mouseCursor

MouseCursor mouseCursor

Flutter MouseCursor