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.
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.
flutter create --sample=material.Radio.1 mysample
See also:
- RadioListTile, which combines this widget with a ListTile so that you can give the radio button a label.
- Slider, for selecting a value in a range.
- Checkbox and Switch, for toggling a particular value on or off.
- material.io/design/components/selection-controls.html#radio-buttons
- Inheritance
Constructors
-
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.
const
Properties
- activeColor → Color?
-
The color to use when this radio button is selected.
final
- autofocus → bool
-
True if this widget will be selected as the initial focus when no other
node in its scope is currently focused.
final
-
fillColor
→ MaterialStateProperty<
Color?> ? -
The color that fills the radio button, in all MaterialStates.
final
- focusColor → Color?
-
The color for the radio's Material when it has the input focus.
final
- focusNode → FocusNode?
-
An optional focus node to use as the focus node for this widget.
final
- groupValue → T?
-
The currently selected value for a group of radio buttons.
final
- hashCode → int
- The hash code for this object.
- hoverColor → Color?
-
The color for the radio's Material when a pointer is hovering over it.
final
- key → Key?
-
Controls how one widget replaces another widget in the tree.
finalinherited
- materialTapTargetSize → MaterialTapTargetSize?
-
Configures the minimum size of the tap target.
final
- mouseCursor → MouseCursor?
-
The cursor for a mouse pointer when it enters or is hovering over the
widget.
final
-
onChanged
→ ValueChanged<
T?> ? -
Called when the user selects this radio button.
final
-
overlayColor
→ MaterialStateProperty<
Color?> ? -
The color for the checkbox's Material.
final
- runtimeType → Type
-
A representation of the runtime type of the object.
read-onlyinherited
- splashRadius → double?
-
The splash radius of the circular Material ink response.
final
- toggleable → bool
-
Set to true if this radio button is allowed to be returned to an
indeterminate state by selecting it again when selected.
final
- value → T
-
The value represented by this radio button.
final
- visualDensity → VisualDensity?
-
Defines how compact the radio's layout will be.
final
Methods
-
createElement(
) → StatefulElement -
Creates a StatefulElement to manage this widget's location in the tree.
inherited
-
createState(
) → State< Radio< T> > -
Creates the mutable state for this widget at a given location in the tree.
override
-
debugDescribeChildren(
) → List< DiagnosticsNode> -
Returns a list of
DiagnosticsNode
objects describing this node's children.protected">@protectedinherited -
debugFillProperties(
DiagnosticPropertiesBuilder properties) → void -
Add additional properties associated with the node.
inherited
-
noSuchMethod(
Invocation invocation) → dynamic -
Invoked when a non-existent 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}) → 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.
nonVirtual">@nonVirtualinherited