HeightObserver class

A widget that observes and reports changes to its child's height.

This widget tracks the height of its child widget, calling the onChange callback whenever the height changes. This is particularly useful for input accessory views or other UI elements where height changes need to be communicated to platform implementations.

The height is measured during the layout phase, ensuring accurate measurements based on the widget's final rendered size.

Example usage:

HeightObserver(
  onChange: (height) {
    print('Widget height changed to: $height');
  },
  child: Container(
    height: 44,
    child: TextField(),
  ),
)

Inheritance

• Object
• DiagnosticableTree
• Widget
• RenderObjectWidget
• SingleChildRenderObjectWidget
• HeightObserver

Constructors

HeightObserver({Key? key, required OnWidgetHeightChange onChange, required Widget child})

Creates a HeightObserver widget.

const

Properties

child → Widget?

The widget below this widget in the tree.

final, inherited

hashCode → int

The hash code for this object.

no setter, inherited

key → Key?

Controls how one widget replaces another widget in the tree.

final, inherited

onChange → OnWidgetHeightChange

Callback function called when the child's height changes.

final

runtimeType → Type

A representation of the runtime type of the object.

no setter, inherited

Methods

createElement() → SingleChildRenderObjectElement

RenderObjectWidgets always inflate to a RenderObjectElement subclass.

inherited

createRenderObject(BuildContext context) → HeightObserverRenderObject

Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget.

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

This method is called when a RenderObject that was previously associated with this widget is removed from the render tree. The provided RenderObject will be of the same type as the one created by this widget's createRenderObject method.

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 HeightObserverRenderObject renderObject) → void

Copies the configuration described by this RenderObjectWidget to the given RenderObject, which will be of the same type as returned by this object's createRenderObject.

override

Operators

operator ==(Object other) → bool

The equality operator.

inherited