NullableStatelessWidget class abstract

A StatelessWidget whose nullableBuild may return null.

When nullableBuild returns null, a collapsed placeholder is used that occupies zero space. StreamRow and StreamColumn skip collapsed children when calculating spacing, so a nullable widget that returns null is effectively invisible — no spacing is allocated for it.

When nullableBuild returns a widget, this behaves like a normal StatelessWidget.

Note: The collapsed-child skipping only works inside StreamRow and StreamColumn. In a regular Row or Column, a collapsed child still occupies a spacing slot.

For simple inline cases, consider NullableBuilder instead.

{@tool snippet}

A label that only renders when the message is pinned:

class PinnedLabel extends NullableStatelessWidget {
  const PinnedLabel({super.key, required this.isPinned});

  final bool isPinned;

  @override
  Widget? nullableBuild(BuildContext context) {
    if (!isPinned) return null;
    return const Text('Pinned');
  }
}

{@end-tool}

See also:

• NullableBuilder, for inline nullable children without a subclass.
• NullableStatefulWidget, for a stateful variant.

Inheritance

• Object
• DiagnosticableTree
• Widget
• StatelessWidget
• NullableStatelessWidget

Implementers

• NullableBuilder

Constructors

NullableStatelessWidget({Key? key})

Creates a nullable stateless widget.

const

Properties

hashCode → int

The hash code for this object.

no setter, 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.

no setter, inherited

Methods

build(BuildContext context) → Widget

Describes the part of the user interface represented by this widget.

override

createElement() → StatelessElement

Creates a StatelessElement to manage this widget's location in the tree.

inherited

debugDescribeChildren() → List<DiagnosticsNode>

Returns a list of DiagnosticsNode objects describing this node's children.

inherited

debugFillProperties(DiagnosticPropertiesBuilder properties) → void

Add additional properties associated with the node.

inherited

noSuchMethod(Invocation invocation) → dynamic

Invoked when a nonexistent method or property is accessed.

inherited

nullableBuild(BuildContext context) → Widget?

Describes the part of the user interface represented by this widget.

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, int wrapWidth = 65}) → 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.

inherited