ScrollNotificationObserver class Null safety
Notifies its listeners when a descendant scrolls.
To add a listener to a ScrollNotificationObserver ancestor:
void listener(ScrollNotification notification) {
// Do something, maybe setState()
}
ScrollNotificationObserver.of(context).addListener(listener)
To remove the listener from a ScrollNotificationObserver ancestor:
ScrollNotificationObserver.of(context).removeListener(listener);
Stateful widgets that share an ancestor ScrollNotificationObserver typically add a listener in State.didChangeDependencies (removing the old one if necessary) and remove the listener in their State.dispose method.
This widget is similar to NotificationListener. It supports a listener list instead of just a single listener and its listeners run unconditionally, they do not require a gating boolean return value.
- Inheritance
-
- Object
- DiagnosticableTree
- Widget
- StatefulWidget
- ScrollNotificationObserver
Constructors
- ScrollNotificationObserver({Key? key, required Widget child})
-
Create a ScrollNotificationObserver.
const
Properties
Methods
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → ScrollNotificationObserverState -
Creates the mutable state for this widget at a given location in the tree.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of
DiagnosticsNodeobjects 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) → ScrollNotificationObserverState? - The closest instance of this class that encloses the given context.