Radio<T> class Null safety

A Material Design radio button.

Used to select between a number of mutually exclusive values. When one radio button in a group is selected, the other radio buttons in the group cease to be selected. The values are of type T, the type parameter of the Radio class. Enums are commonly used for this purpose.

The radio button itself does not maintain any state. Instead, selecting the radio invokes the onChanged callback, passing value as a parameter. If groupValue and value match, this radio will be selected. Most widgets will respond to onChanged by calling State.setState to update the radio button's groupValue.

Here is an example of Radio widgets wrapped in ListTiles, which is similar to what you could get with the RadioListTile widget.

The currently selected character is passed into groupValue, which is maintained by the example's State. In this case, the first Radio will start off selected because _character is initialized to SingingCharacter.lafayette.

If the second radio button is pressed, the example's state is updated with setState, updating _character to SingingCharacter.jefferson. This causes the buttons to rebuild with the updated groupValue, and therefore the selection of the second button.

Requires one of its ancestors to be a Material widget.

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

See also:



Radio({Key? key, required T value, required T? groupValue, required ValueChanged<T?>? onChanged, MouseCursor? mouseCursor, bool toggleable = false, Color? activeColor, MaterialStateProperty<Color?>? fillColor, Color? focusColor, Color? hoverColor, MaterialStateProperty<Color?>? overlayColor, double? splashRadius, MaterialTapTargetSize? materialTapTargetSize, VisualDensity? visualDensity, FocusNode? focusNode, bool autofocus = false})
Creates a Material Design radio button.


activeColor Color?
The color to use when this radio button is selected.
autofocus bool
True if this widget will be selected as the initial focus when no other node in its scope is currently focused.
fillColor MaterialStateProperty<Color?>?
The color that fills the radio button, in all MaterialStates.
focusColor Color?
The color for the radio's Material when it has the input focus.
focusNode FocusNode?
An optional focus node to use as the focus node for this widget.
groupValue → T?
The currently selected value for a group of radio buttons.
hashCode int
The hash code for this object.
@nonVirtual, read-only, inherited
hoverColor Color?
The color for the radio's Material when a pointer is hovering over it.
key Key?
Controls how one widget replaces another widget in the tree.
final, inherited
materialTapTargetSize MaterialTapTargetSize?
Configures the minimum size of the tap target.
mouseCursor MouseCursor?
The cursor for a mouse pointer when it enters or is hovering over the widget.
onChanged ValueChanged<T?>?
Called when the user selects this radio button.
overlayColor MaterialStateProperty<Color?>?
The color for the checkbox's Material.
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
splashRadius double?
The splash radius of the circular Material ink response.
toggleable bool
Set to true if this radio button is allowed to be returned to an indeterminate state by selecting it again when selected.
value → T
The value represented by this radio button.
visualDensity VisualDensity?
Defines how compact the radio's layout will be.


createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
createState() State<Radio<T>>
Creates the mutable state for this widget at a given location in the tree.
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.
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.


operator ==(Object other) bool
The equality operator.
@nonVirtual, inherited