MergeSemantics class Null safety

A widget that merges the semantics of its descendants.

Causes all the semantics of the subtree rooted at this node to be merged into one node in the semantics tree. For example, if you have a widget with a Text node next to a checkbox widget, this could be used to merge the label from the Text node with the "checked" semantic state of the checkbox into a single node that had both the label and the checked state. Otherwise, the label would be presented as a separate feature than the checkbox, and the user would not be able to be sure that they were related.

link
This snippet shows how to use MergeSemantics to merge the semantics of a Checkbox and Text widget. 
MergeSemantics(
  child: Row(
    children: <Widget>[
      Checkbox(
        value: true,
        onChanged: (bool? value) {},
      ),
      const Text('Settings'),
    ],
  ),
)

Be aware that if two nodes in the subtree have conflicting semantics, the result may be nonsensical. For example, a subtree with a checked checkbox and an unchecked checkbox will be presented as checked. All the labels will be merged into a single string (with newlines separating each label from the other). If multiple nodes in the merged subtree can handle semantic gestures, the first one in tree order will be the one to receive the callbacks.

Inheritance

Constructors

MergeSemantics({Key? key, Widget? child})
Creates a widget that merges the semantics of its descendants.
const

Properties

child → Widget?
The widget below this widget in the tree.
finalinherited
hashCode → int
The hash code for this object.
nonVirtual">@nonVirtualread-onlyinherited
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited

Methods

createElement() → SingleChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
inherited
createRenderObject(BuildContext context) → RenderMergeSemantics
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.
protected">@protectedinherited
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">@protectedinherited
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 RenderObject 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.
protected">@protectedinherited

Operators

operator ==(Object other) → bool
The equality operator.
nonVirtual">@nonVirtualinherited