ParentDataWidget<T extends RenderObjectWidget> class

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 RenderObject, and thus also to a particular RenderObjectWidget class. That class is T, the ParentDataWidget 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<FrogJar> {
  FrogSize({
    Key key,
    @required this.size,
    @required Widget child,
  }) : assert(child != null),
       assert(size != null),
       super(key: key, child: child);

  final Size size;

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

Constructors

ParentDataWidget({Key key, 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
hashCode → int: The hash code for this object. [...]
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
debugDescribeInvalidAncestorChain({String description, DiagnosticsNode ownershipChain, bool foundValidAncestor, Iterable<Widget> badAncestors }) → Iterable<DiagnosticsNode>: Subclasses should override this to describe the requirements for using the ParentDataWidget subclass. It is called when debugIsValidAncestor() returned false for an ancestor, or when there are extraneous ParentDataWidgets in the ancestor chain.
debugIsValidAncestor(RenderObjectWidget ancestor) → bool: Subclasses should override this method to return true if the given ancestor is a RenderObjectWidget that wraps a RenderObject that can handle the kind of ParentData widget that the ParentDataWidget subclass handles. [...]
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
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.debug }) → String: Returns 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 ==(dynamic other) → bool: The equality operator. [...]
inherited

widgets library

ParentDataWidget<T extends RenderObjectWidget> class

Constructors

Properties

Methods

Operators