CustomBoxy class

A widget that uses a delegate to control the layout of multiple children.

This is basically a much more powerful version of CustomMultiChildLayout, it allows you to inflate, constrain, and lay out each child manually, it also allows the size of the widget to depend on the layout of its children.

In most cases you do not need this much control over layout where some combination of Stack, LayoutBuilder, and Flow is more suitable.

Children can be wrapped in a LayoutId widget to give them an arbitrary Object id to be accessed by the BoxyDelegate, otherwise they are given an incrementing int id in the order they are provided, for example:

  delegate: MyBoxyDelegate(),
  children: [
    Container(color:, // Child 0
    LayoutId(id: #green, child: Container(color:,
    Container(color:, // Child 1

See also:



CustomBoxy({Key key, @required BoxyDelegate<Object> delegate, List<Widget> children = const <Widget>[]})
Constructs a CustomBoxy with a delegate and optional set of children.


children List<Widget>
The list of children this boxy is a parent of.
delegate BoxyDelegate<Object>
The delegate that controls the layout of the children.
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


createElement() → _RenderBoxyElement
RenderObjectWidgets always inflate to a RenderObjectElement subclass.
createRenderObject(BuildContext context) → _RenderBoxy
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. [...]
@protected, inherited
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.
@protected, inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a non-existent 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 _RenderBoxy 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. [...]
@nonVirtual, inherited