AppBar class
A material design app bar.
An app bar consists of a toolbar and potentially other widgets, such as a TabBar and a FlexibleSpaceBar. App bars typically expose one or more common actions with IconButtons which are optionally followed by a PopupMenuButton for less common operations (sometimes called the "overflow menu").
App bars are typically used in the Scaffold.appBar property, which places the app bar as a fixed-height widget at the top of the screen. For a scrollable app bar, see SliverAppBar, which embeds an AppBar in a sliver for use in a CustomScrollView.
The AppBar displays the toolbar widgets, leading, title, and actions, above the bottom (if any). The bottom is usually used for a TabBar. If a flexibleSpace widget is specified then it is stacked behind the toolbar and the bottom widget. The following diagram shows where each of these slots appears in the toolbar when the writing language is left-to-right (e.g. English):
If the leading widget is omitted, but the AppBar is in a Scaffold with a Drawer, then a button will be inserted to open the drawer. Otherwise, if the nearest Navigator has any previous routes, a BackButton is inserted instead. This behavior can be turned off by setting the automaticallyImplyLeading to false. In that case a null leading widget will result in the middle/title widget stretching to start.
AppBar(
title: Text('My Fancy Dress'),
actions: <Widget>[
IconButton(
icon: Icon(Icons.playlist_play),
tooltip: 'Air it',
onPressed: _airDress,
),
IconButton(
icon: Icon(Icons.playlist_add),
tooltip: 'Restitch it',
onPressed: _restitchDress,
),
IconButton(
icon: Icon(Icons.playlist_add_check),
tooltip: 'Repair it',
onPressed: _repairDress,
),
],
)
See also:
- Scaffold, which displays the AppBar in its Scaffold.appBar slot.
- SliverAppBar, which uses AppBar to provide a flexible app bar that can be used in a CustomScrollView.
- TabBar, which is typically placed in the bottom slot of the AppBar if the screen has multiple pages arranged in tabs.
- IconButton, which is used with actions to show buttons on the app bar.
- PopupMenuButton, to show a popup menu on the app bar, via actions.
- FlexibleSpaceBar, which is used with flexibleSpace when the app bar can expand and collapse.
- material.google.com/layout/structure.html#structure-toolbars
- Inheritance
- Implemented types
Constructors
-
AppBar({Key key, Widget leading, bool automaticallyImplyLeading: true, Widget title, List<
Widget> actions, Widget flexibleSpace, PreferredSizeWidget bottom, double elevation: 4.0, Color backgroundColor, Brightness brightness, IconThemeData iconTheme, TextTheme textTheme, bool primary: true, bool centerTitle, double titleSpacing: NavigationToolbar.kMiddleSpacing, double toolbarOpacity: 1.0, double bottomOpacity: 1.0 }) - Creates a material design app bar. [...]
Properties
-
actions
→ List<
Widget> -
Widgets to display after the title widget. [...]
final
- automaticallyImplyLeading → bool
-
Controls whether we should try to imply the leading widget if null. [...]
final
- backgroundColor → Color
-
The color to use for the app bar's material. Typically this should be set
along with brightness, iconTheme, textTheme. [...]
final
- bottom → PreferredSizeWidget
-
This widget appears across the bottom of the app bar. [...]
final
- bottomOpacity → double
-
How opaque the bottom part of the app bar is. [...]
final
- brightness → Brightness
-
The brightness of the app bar's material. Typically this is set along
with backgroundColor, iconTheme, textTheme. [...]
final
- centerTitle → bool
-
Whether the title should be centered. [...]
final
- elevation → double
-
The z-coordinate at which to place this app bar. This controls the size of
the shadow below the app bar. [...]
final
- flexibleSpace → Widget
-
This widget is stacked behind the toolbar and the tabbar. It's height will
be the same as the app bar's overall height. [...]
final
- iconTheme → IconThemeData
-
The color, opacity, and size to use for app bar icons. Typically this
is set along with backgroundColor, brightness, textTheme. [...]
final
- leading → Widget
-
A widget to display before the title. [...]
final
- preferredSize → Size
-
A size whose height is the sum of kToolbarHeight and the bottom widget's
preferred height. [...]
final
- primary → bool
-
Whether this app bar is being displayed at the top of the screen. [...]
final
- textTheme → TextTheme
-
The typographic styles to use for text in the app bar. Typically this is
set along with brightness backgroundColor, iconTheme. [...]
final
- title → Widget
-
The primary widget displayed in the appbar. [...]
final
- titleSpacing → double
-
The spacing around title content on the horizontal axis. This spacing is
applied even if there is no leading content or actions. If you want
title to take all the space available, set this value to 0.0. [...]
final
- toolbarOpacity → double
-
How opaque the toolbar part of the app bar is. [...]
final
- hashCode → int
-
The hash code for this object. [...]
read-only, inherited
- key → Key
-
Controls how one widget replaces another widget in the tree. [...]
final, inherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-only, inherited
Methods
-
createState(
) → _AppBarState -
Creates the mutable state for this widget at a given location in the tree. [...]
override
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree. [...]
inherited
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of DiagnosticsNode objects describing this node's
children. [...]
@protected, inherited
-
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node. [...]
inherited
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent 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 toStringDeep. [...]
inherited
-
toString(
{DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String -
Returns 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 ==(
dynamic other) → bool -
The equality operator. [...]
inherited