VisibilityDetector class Null safety

A VisibilityDetector widget fires a specified callback when the widget changes visibility.

Callbacks are not fired immediately on visibility changes. Instead, callbacks are deferred and coalesced such that the callback for each VisibilityDetector will be invoked at most once per VisibilityDetectorController.updateInterval (unless forced by VisibilityDetectorController.notifyNow). Callbacks for all VisibilityDetector widgets are fired together synchronously between frames.

Inheritance

Constructors

VisibilityDetector({required Key key, required Widget child, required VisibilityChangedCallback? onVisibilityChanged})
Constructor. [...]
const

Properties

child Widget?
The widget below this widget in the tree. [...]
final, inherited
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
onVisibilityChanged VisibilityChangedCallback?
The callback to invoke when this widget's visibility changes.
final
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

createElement() SingleChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
createRenderObject(BuildContext context) → RenderVisibilityDetector
See RenderObjectWidget.createRenderObject.
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
didUnmountRenderObject(covariant RenderObject renderObject) → void
A render object previously associated with this widget has been removed from the tree. The given RenderObject will be of the same type as returned by this object's createRenderObject.
@protected, 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
updateRenderObject(BuildContext context, covariant RenderVisibilityDetector renderObject) → void
See RenderObjectWidget.updateRenderObject.
override

Operators

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