CustomMultiChildLayout class

A widget that uses a delegate to size and position multiple children.

The delegate can determine the layout constraints for each child and can decide where to position each child. The delegate can also determine the size of the parent, but the size of the parent cannot depend on the sizes of the children.

CustomMultiChildLayout is appropriate when there are complex relationships between the size and positioning of multiple widgets. To control the layout of a single child, CustomSingleChildLayout is more appropriate. For simple cases, such as aligning a widget to one or another edge, the Stack widget is more appropriate.

Each child must be wrapped in a LayoutId widget to identify the widget for the delegate.

This example shows a CustomMultiChildLayout widget being used to lay out colored blocks from start to finish in a cascade that has some overlap.

It responds to changes in Directionality by re-laying out its children.


To create a local project with this code sample, run:
flutter create --sample=widgets.CustomMultiChildLayout.1 mysample

See also:



CustomMultiChildLayout({Key? key, required MultiChildLayoutDelegate delegate, List<Widget> children = const <Widget>[]})
Creates a custom multi-child layout.


children List<Widget>
The widgets below this widget in the tree.
delegate MultiChildLayoutDelegate
The delegate that controls the layout of the children.
hashCode int
The hash code for this object.
no setterinherited
key Key?
Controls how one widget replaces another widget in the tree.
runtimeType Type
A representation of the runtime type of the object.
no setterinherited


createElement() MultiChildRenderObjectElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
createRenderObject(BuildContext context) RenderCustomMultiChildLayoutBox
Creates an instance of the RenderObject class that this RenderObjectWidget represents, using the configuration described by this RenderObjectWidget.
debugDescribeChildren() List<DiagnosticsNode>
Returns a list of DiagnosticsNode objects describing this node's children.
debugFillProperties(DiagnosticPropertiesBuilder properties) → void
Add additional properties associated with the node.
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.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
toDiagnosticsNode({String? name, DiagnosticsTreeStyle? style}) DiagnosticsNode
Returns a debug representation of the object that is used by debugging tools and by DiagnosticsNode.toStringDeep.
toString({DiagnosticLevel minLevel =}) String
A string representation of this object.
toStringDeep({String prefixLineOne = '', String? prefixOtherLines, DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a string representation of this node and its descendants.
toStringShallow({String joiner = ', ', DiagnosticLevel minLevel = DiagnosticLevel.debug}) String
Returns a one-line detailed description of the object.
toStringShort() String
A short, textual description of this widget.
updateRenderObject(BuildContext context, covariant RenderCustomMultiChildLayoutBox 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.


operator ==(Object other) bool
The equality operator.