FlexibleSpaceBar class Null safety

The part of a material design AppBar that expands, collapses, and stretches.

Most commonly used in the SliverAppBar.flexibleSpace field, a flexible space bar expands and contracts as the app scrolls so that the AppBar reaches from the top of the app to the top of the scrolling contents of the app. When using SliverAppBar.flexibleSpace, the SliverAppBar.expandedHeight must be large enough to accommodate the SliverAppBar.flexibleSpace widget.

Furthermore is included functionality for stretch behavior. When SliverAppBar.stretch is true, and your ScrollPhysics allow for overscroll, this space will stretch with the overscroll.

The widget that sizes the AppBar must wrap it in the widget returned by FlexibleSpaceBar.createSettings, to convey sizing information down to the FlexibleSpaceBar.

This sample application demonstrates the different features of the FlexibleSpaceBar when used in a SliverAppBar. This app bar is configured to stretch into the overscroll space, and uses the FlexibleSpaceBar.stretchModes to apply fadeTitle, blurBackground and zoomBackground. The app bar also makes use of CollapseMode.parallax by default.
To create a local project with this code sample, run:
flutter create --sample=material.FlexibleSpaceBar.1 mysample

See also:



FlexibleSpaceBar({Key? key, Widget? title, Widget? background, bool? centerTitle, EdgeInsetsGeometry? titlePadding, CollapseMode collapseMode, List<StretchMode> stretchModes})
Creates a flexible space bar. [...]


background Widget?
Shown behind the title when expanded. [...]
centerTitle bool?
Whether the title should be centered. [...]
collapseMode CollapseMode
Collapse effect while scrolling. [...]
hashCode int
The hash code for this object. [...]
@nonVirtual, 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
stretchModes List<StretchMode>
Stretch effect while over-scrolling. [...]
title Widget?
The primary contents of the flexible space bar when expanded. [...]
titlePadding EdgeInsetsGeometry?
Defines how far the title is inset from either the widget's bottom-left or its center. [...]


createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree. [...]
createState() State<FlexibleSpaceBar>
Creates the mutable state for this widget at a given location in the tree. [...]
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. [...]
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent method or property is accessed. [...]
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep. [...]
toString({DiagnosticLevel minLevel = DiagnosticLevel.info}) String
A string representation of this object. [...]
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a string representation of this node and its descendants. [...]
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a one-line detailed description of the object. [...]
toStringShort() String
A short, textual description of this widget.


operator ==(Object other) bool
The equality operator. [...]
@nonVirtual, inherited

Static Methods

createSettings({double? toolbarOpacity, double? minExtent, double? maxExtent, bool? isScrolledUnder, required double currentExtent, required Widget child}) Widget
Wraps a widget that contains an AppBar to convey sizing information down to the FlexibleSpaceBar. [...]