NewGradientAppBar 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 SliverNewGradientAppBar, which embeds an NewGradientAppBar in a sliver for use in a CustomScrollView.

When not used as Scaffold.appBar, or when wrapped in a Hero, place the app bar in a MediaQuery to take care of the padding around the content of the app bar if needed, as the padding will not be handled by Scaffold.

The GradientAppBar 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):

The leading widget is in the top left, the actions are in the top right, the title is between them. The bottom is, naturally, at the bottom, and the flexibleSpace is behind all of them.

If the leading widget is omitted, but the NewGradientAppBar 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.

{@tool snippet --template=stateless_widget_material}

This sample shows an NewGradientAppBar with two simple actions. The first action opens a SnackBar, while the second action navigates to a new page.

final GlobalKey<ScaffoldState> scaffoldKey = GlobalKey<ScaffoldState>();
final SnackBar snackBar = const SnackBar(content: Text('Showing Snackbar'));

void openPage(BuildContext context) {
  Navigator.push(context, MaterialPageRoute(
    builder: (BuildContext context) {
      return Scaffold(
        appBar: GradientAppBar(
          title: const Text('Next page'),
        ),
        body: const Center(
          child: Text(
            'This is the next page',
            style: TextStyle(fontSize: 24),
          ),
        ),
      );
    },
  ));
}

Widget build(BuildContext context) {
  return Scaffold(
    key: scaffoldKey,
    appBar: GradientAppBar(
      title: const Text('GradientAppBar Demo'),
      actions: <Widget>[
        IconButton(
          icon: const Icon(Icons.add_alert),
          tooltip: 'Show Snackbar',
          onPressed: () {
            scaffoldKey.currentState.showSnackBar(snackBar);
          },
        ),
        IconButton(
          icon: const Icon(Icons.navigate_next),
          tooltip: 'Next page',
          onPressed: () {
            openPage(context);
          },
        ),
      ],
    ),
    body: const Center(
      child: Text(
        'This is the home page',
        style: TextStyle(fontSize: 24),
      ),
    ),
  );
}

{@end-tool}

See also:

Inheritance
Implemented types

Constructors

NewGradientAppBar({Key? key, Widget? leading, bool automaticallyImplyLeading = true, Widget? title, List<Widget>? actions, Widget? flexibleSpace, PreferredSizeWidget? bottom, double? elevation, ShapeBorder? shape, Gradient? gradient, Brightness? brightness, IconThemeData? iconTheme, IconThemeData? actionsIconTheme, 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
actionsIconTheme → IconThemeData?
The color, opacity, and size to use for the icons that appear in the app bar's actions. This should only be used when the actions should be themed differently than the icon that appears in the app bar's leading widget.
final
automaticallyImplyLeading → bool
Controls whether we should try to imply the leading widget if null.
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 gradient displayed at the appbar.
final
centerTitle → bool?
Whether the title should be centered.
final
elevation → double?
The z-coordinate at which to place this app bar relative to its parent.
final
flexibleSpace → Widget?
This widget is stacked behind the toolbar and the tab bar. It's height will be the same as the app bar's overall height.
final
gradient → Gradient?
The color to use for the app bar's material. Typically this should be set along with brightness, iconTheme, textTheme.
final
hashCode → int
The hash code for this object.
no setterinherited
iconTheme → IconThemeData?
The color, opacity, and size to use for app bar icons. Typically this is set along with backgroundColor, brightness, textTheme.
final
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
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
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited
shape → ShapeBorder?
The material's shape as well its shadow.
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

Methods

createElement() → StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() → _NewGradientAppBarState
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