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

Constructors

ScrollNotificationObserver({Key? key, required Widget child})
Create a ScrollNotificationObserver. [...]
const

Properties

child Widget
The subtree below this widget.
final
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

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 DiagnosticsNode objects describing this node's children. [...]
@protected, inherited
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, inherited

Static Methods

of(BuildContext context) ScrollNotificationObserverState?
The closest instance of this class that encloses the given context. [...]