VisibilityDetector class
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
-
- Object
- DiagnosticableTree
- Widget
- RenderObjectWidget
- SingleChildRenderObjectWidget
- VisibilityDetector
Constructors
- VisibilityDetector({required Key key, required Widget child, required VisibilityChangedCallback? onVisibilityChanged, double visibleFraction = 1, bool triggerOnce = true})
-
Constructor.
const
Properties
- child → Widget?
-
The widget below this widget in the tree.
finalinherited
- hashCode → int
-
The hash code for this object.
no setterinherited
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- onVisibilityChanged → VisibilityChangedCallback?
-
The callback to invoke when this widget's visibility changes.
final
- runtimeType → Type
-
A representation of the runtime type of the object.
no setterinherited
- triggerOnce → bool
-
final
- visibleFraction → double
-
final
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.
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.
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, int wrapWidth = 65}) → 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.
inherited