CustomBottomNavigationBar class

A material widget that's displayed at the bottom of an app for selecting among a small number of views, typically between three and five.

The bottom navigation bar consists of multiple items in the form of text labels, icons, or both, laid out on top of a piece of material. It provides quick navigation between the top-level views of an app. For larger screens, side navigation may be a better fit.

A bottom navigation bar is usually used in conjunction with a Scaffold, where it is provided as the Scaffold.bottomNavigationBar argument.

The bottom navigation bar's type changes how its items are displayed. If not specified, then it's automatically set to BottomNavigationBarType.fixed when there are less than four items, and BottomNavigationBarType.shifting otherwise.

The length of items must be at least two and each item's icon and title/label must not be null.

• BottomNavigationBarType.fixed, the default when there are less than four items. The selected item is rendered with the selectedItemColor if it's non-null, otherwise the theme's ThemeData.primaryColor is used. If backgroundColor is null, The navigation bar's background color defaults to the Material background color, ThemeData.canvasColor (essentially opaque white).
• BottomNavigationBarType.shifting, the default when there are four or more items. If selectedItemColor is null, all items are rendered in white. The navigation bar's background color is the same as the BottomNavigationBarItem.backgroundColor of the selected item. In this case it's assumed that each item will have a different background color and that background color will contrast well with white.

{@tool dartpad --template=stateful_widget_material} This example shows a BottomNavigationBar as it is used within a Scaffold widget. The BottomNavigationBar has three BottomNavigationBarItem widgets, which means it defaults to BottomNavigationBarType.fixed, and the currentIndex is set to index 0. The selected item is amber. The _onItemTapped function changes the selected item's index and displays a corresponding message in the center of the Scaffold.

int _selectedIndex = 0;
static const TextStyle optionStyle = TextStyle(fontSize: 30, fontWeight: FontWeight.bold);
static const List<Widget> _widgetOptions = <Widget>[
  Text(
    'Index 0: Home',
    style: optionStyle,
  ),
  Text(
     'Index 1: Business',
     style: optionStyle,
  ),
  Text(
     'Index 2: School',
     style: optionStyle,
  ),
];

void _onItemTapped(int index) {
  setState(() {
    _selectedIndex = index;
  });
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: const Text('BottomNavigationBar Sample'),
    ),
    body: Center(
      child: _widgetOptions.elementAt(_selectedIndex),
    ),
    bottomNavigationBar: BottomNavigationBar(
      items: const <BottomNavigationBarItem>[
        BottomNavigationBarItem(
          icon: Icon(Icons.home),
          label: 'Home',
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.business),
          label: 'Business',
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.school),
          label: 'School',
        ),
      ],
      currentIndex: _selectedIndex,
      selectedItemColor: Colors.amber[800],
      onTap: _onItemTapped,
    ),
  );
}

{@end-tool}

{@tool dartpad --template=stateful_widget_material} This example shows a BottomNavigationBar as it is used within a Scaffold widget. The BottomNavigationBar has four BottomNavigationBarItem widgets, which means it defaults to BottomNavigationBarType.shifting, and the currentIndex is set to index 0. The selected item is amber in color. With each BottomNavigationBarItem widget, backgroundColor property is also defined, which changes the background color of BottomNavigationBar, when that item is selected. The _onItemTapped function changes the selected item's index and displays a corresponding message in the center of the Scaffold.

int _selectedIndex = 0;
static const TextStyle optionStyle = TextStyle(fontSize: 30, fontWeight: FontWeight.bold);
static const List<Widget> _widgetOptions = <Widget>[
  Text(
    'Index 0: Home',
    style: optionStyle,
  ),
  Text(
    'Index 1: Business',
    style: optionStyle,
  ),
  Text(
    'Index 2: School',
    style: optionStyle,
  ),
  Text(
    'Index 3: Settings',
    style: optionStyle,
  ),
];

void _onItemTapped(int index) {
  setState(() {
    _selectedIndex = index;
  });
}

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(
      title: const Text('BottomNavigationBar Sample'),
    ),
    body: Center(
      child: _widgetOptions.elementAt(_selectedIndex),
    ),
    bottomNavigationBar: BottomNavigationBar(
      items: const <BottomNavigationBarItem>[
        BottomNavigationBarItem(
          icon: Icon(Icons.home),
          label: 'Home',
          backgroundColor: Colors.red,
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.business),
          label: 'Business',
          backgroundColor: Colors.green,
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.school),
          label: 'School',
          backgroundColor: Colors.purple,
        ),
        BottomNavigationBarItem(
          icon: Icon(Icons.settings),
          label: 'Settings',
          backgroundColor: Colors.pink,
        ),
      ],
      currentIndex: _selectedIndex,
      selectedItemColor: Colors.amber[800],
      onTap: _onItemTapped,
    ),
  );
}

{@end-tool} See also:

• BottomNavigationBarItem
• Scaffold
• material.io/design/components/bottom-navigation.html

Inheritance

• Object
• DiagnosticableTree
• Widget
• StatefulWidget
• CustomBottomNavigationBar

Constructors

CustomBottomNavigationBar({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, bool? showUnselectedLabels, MouseCursor? mouseCursor})

Creates a bottom navigation bar which is typically used as a Scaffold's Scaffold.bottomNavigationBar argument.

Properties

backgroundColor → Color?

The color of the BottomNavigationBar itself.

final

currentIndex → int

The index into items for the current active BottomNavigationBarItem.

final

elevation → double?

The z-coordinate of this BottomNavigationBar.

final

fixedColor → Color?

The value of selectedItemColor.

no setter

hashCode → int

The hash code for this object.

no setter, inherited

iconSize → double

The size of all of the BottomNavigationBarItem icons.

final

items → List<BottomNavigationBarItem>

Defines the appearance of the button items that are arrayed within the bottom navigation bar.

final

key → Key?

Controls how one widget replaces another widget in the tree.

final, inherited

mouseCursor → MouseCursor?

The cursor for a mouse pointer when it enters or is hovering over the tiles.

final

onTap → ValueChanged<int>?

Called when one of the items is tapped.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

selectedFontSize → double

The font size of the BottomNavigationBarItem labels when they are selected.

final

selectedIconTheme → IconThemeData?

The size, opacity, and color of the icon in the currently selected BottomNavigationBarItem.icon.

final

selectedItemColor → Color?

The color of the selected BottomNavigationBarItem.icon and BottomNavigationBarItem.title.

final

selectedLabelStyle → TextStyle?

The TextStyle of the BottomNavigationBarItem labels when they are selected.

final

showSelectedLabels → bool?

Whether the labels are shown for the selected BottomNavigationBarItem.

final

showUnselectedLabels → bool?

Whether the labels are shown for the unselected BottomNavigationBarItems.

final

type → BottomNavigationBarType?

Defines the layout and behavior of a BottomNavigationBar.

final

unselectedFontSize → double

The font size of the BottomNavigationBarItem labels when they are not selected.

final

unselectedIconTheme → IconThemeData?

The size, opacity, and color of the icon in the currently unselected BottomNavigationBarItem.icons.

final

unselectedItemColor → Color?

The color of the unselected BottomNavigationBarItem.icon and BottomNavigationBarItem.titles.

final

unselectedLabelStyle → TextStyle?

The TextStyle of the BottomNavigationBarItem labels when they are not selected.

final

Methods

createElement() → StatefulElement

Creates a StatefulElement to manage this widget's location in the tree.

inherited

createState() → _BottomNavigationBarState

Creates the mutable state for this widget at a given location in the tree.

override

debugDescribeChildren() → List<DiagnosticsNode>

Returns a list of DiagnosticsNode objects describing this node's children.

inherited

debugFillProperties(DiagnosticPropertiesBuilder properties) → void

Add additional properties associated with the node.

inherited

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) → DiagnosticsNode

Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.

inherited

toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) → String

A string representation of this object.

inherited

toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String

Returns a string representation of this node and its descendants.

inherited

toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) → String

Returns a one-line detailed description of the object.

inherited

toStringShort() → String

A short, textual description of this widget.

inherited

Operators

operator ==(Object other) → bool

The equality operator.

inherited