ParentDataWidget<T extends ParentData> class Null safety

Base class for widgets that hook ParentData information to children of RenderObjectWidgets.

This can be used to provide per-child configuration for RenderObjectWidgets with more than one child. For example, Stack uses the Positioned parent data widget to position each child.

A ParentDataWidget is specific to a particular kind of ParentData. That class is T, the ParentData type argument.

This example shows how you would build a ParentDataWidget to configure a FrogJar widget's children by specifying a Size for each one.

class FrogSize extends ParentDataWidget<FrogJarParentData> {
  const FrogSize({
    Key? key,
    required this.size,
    required Widget child,
  }) : super(key: key, child: child);

  final Size size;

  @override
  void applyParentData(RenderObject renderObject) {
    final FrogJarParentData parentData = renderObject.parentData! as FrogJarParentData;
    if (parentData.size != size) {
      parentData.size = size;
      final RenderFrogJar targetParent = renderObject.parent! as RenderFrogJar;
      targetParent.markNeedsLayout();
    }
  }

  @override
  Type get debugTypicalAncestorWidgetClass => FrogJar;
}

Constructors

ParentDataWidget({Key? key, required Widget child}): Abstract const constructor. This constructor enables subclasses to provide const constructors so that they can be used in const expressions.
const

Properties

child → Widget: The widget below this widget in the tree. [...]
final, inherited
debugTypicalAncestorWidgetClass → Type: The RenderObjectWidget that is typically used to set up the ParentData that applyParentData will write to. [...]
read-only
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

applyParentData(RenderObject renderObject) → void: Write the data from this widget into the given render object's parent data. [...]
@protected
createElement() → ParentDataElement<T>: Inflates this configuration to a concrete instance. [...]
override
debugCanApplyOutOfTurn() → bool: Whether the ParentDataElement.applyWidgetOutOfTurn method is allowed with this widget. [...]
@protected
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
debugIsValidRenderObject(RenderObject renderObject) → bool: Checks if this widget can apply its parent data to the provided renderObject. [...]
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

Flutter
widgets
ParentDataWidget<T extends ParentData> abstract class

ParentDataWidget<T extends ParentData> class Null safety

Constructors

Properties

Methods

Operators

widgets library