CellWidget class abstract

A widget which is rebuilt in response to changes in the values of ValueCell's.

When the value of a ValueCell is referenced within the build method, using ValueCell.call, the widget is automatically rebuilt whenever the value of the referenced cell changes.

Example:

class Example extends WidgetCell {
  final ValueCell<int> a;

  Example({
    super.key
    required this.a
  });

  @override
  Widget build(BuildContext context) {
    return Text('The value of cell a is ${a()}');
  }
}

In the above example, the widget is rebuilt automatically whenever the value of cell a is changed.

Cells defined directly within the build will have their state persisted between builds. For this to happen the following rules have to be observed:

1. Cells should not be defined in conditionals or loops.
2. Cells should not be defined in callback or builder functions of widgets nested in this widget.

The following is an example of correctly placed cell definitions:

@override
Widget build (BuildContext context) {
  final count = MutableCell(0);
  final next = ValueCell.computed(() => count() + 1);
  ...
}

The following is an example of incorrectly placed cell definitions:

@override
Widget build (BuildContext context) {
  if (...) {
    // This is bad because the definition appears within a conditional
    final count = MutableCell(0);
  }

  while (...) {
    // This is bad because the definition appears within a loop
    final count = MutableCell(0);
  }

  return Builder((context) {
    // This is bad because the definition appears in a builder function
    // of a nested widget and the [CellWidget] will not be able to persist
    // its state between builds.
    final count = MutableCell(0);
  });
}

Inheritance

• Object
• DiagnosticableTree
• Widget
• StatelessWidget
• CellWidget

Constructors

CellWidget({Key? key, String? restorationId})

const

CellWidget.builder(Widget builder(CellHookContext context), {Key? key, String? restorationId})

Create a CellWidget with the build method defined by builder.

factory

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

restorationId → String?

Restoration ID to use for restoring the cell state

final

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.

inherited

createElement() → StatelessElement

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

override

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

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