PageStorage class Null safety
Establish a subtree in which widgets can opt into persisting states after being destroyed.
PageStorage is used to save and restore values that can outlive the widget. For example, when multiple pages are grouped in tabs, when a page is switched out, its widget is destroyed and its state is lost. By adding a PageStorage at the root and adding a PageStorageKey to each page, some of the page's state (e.g. the scroll position of a Scrollable widget) will be stored automatically in its closest ancestor PageStorage, and restored when it's switched back.
Usually you don't need to explicitly use a PageStorage, since it's already included in routes.
PageStorageKey is used by Scrollable if ScrollController.keepScrollOffset
is enabled to save their ScrollPositions. When more than one
scrollable (ListView, SingleChildScrollView, TextField, etc.) appears
within the widget's closest ancestor PageStorage (such as within the same route),
if you want to save all of their positions independently,
you should give each of them unique PageStorageKeys, or set some of their
keepScrollOffset
false to prevent saving.
flutter create --sample=widgets.PageStorage.1 mysample
See also:
- ModalRoute, which includes this class.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatelessWidget
- PageStorage
Constructors
- PageStorage({Key? key, required PageStorageBucket bucket, required Widget child})
-
Creates a widget that provides a storage bucket for its descendants.
const
Properties
- bucket → PageStorageBucket
-
The page storage bucket to use for this subtree.
final
- child → Widget
-
The widget below this widget in the tree.
final
- hashCode → int
- The hash code for this object.
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
read-onlyinherited
Methods
-
build(
BuildContext context) → Widget -
Describes the part of the user interface represented by this widget.
override
-
createElement(
) → StatelessElement -
Creates a StatelessElement 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">@protectedinherited -
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 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.
nonVirtual">@nonVirtualinherited
Static Methods
-
of(
BuildContext context) → PageStorageBucket? - The bucket from the closest instance of this class that encloses the given context.