PageStorageModifier class
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.
{@tool dartpad} This sample shows how to explicitly use a PageStorage to store the states of its children pages. Each page includes a scrollable list, whose position is preserved when switching between the tabs thanks to the help of PageStorageKey.
** See code in examples/api/lib/widgets/page_storage/page_storage.0.dart ** {@end-tool}
See also:
- ModalRoute, which includes this class.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatelessWidget
- SingleChildStatelessModifier
- PageStorageModifier
- Available extensions
Constructors
- PageStorageModifier({Key? key, Widget? child, Key? modifierKey, required PageStorageBucket bucket})
-
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
- hashCode → int
-
The hash code for this object.
no setterinherited
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- modifierKey → Key?
-
The actual key of the widget, which Modifier wrapped
finalinherited
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
Methods
-
build(
BuildContext context) → Widget -
Describes the part of the user interface represented by this widget.
inherited
-
buildWithChild(
BuildContext context, Widget? child) → Widget -
A build method that receives an extra
childparameter.override -
createElement(
) → SingleChildStatelessElement -
Create a SingleChildStatelessElement
inherited
-
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