DropdownButtonFormField<T> class Null safety

A FormField that contains a DropdownButton.

This is a convenience widget that wraps a DropdownButton widget in a FormField.

A Form ancestor is not required. The Form simply makes it easier to save, reset, or validate multiple fields at once. To use without a Form, pass a GlobalKey to the constructor and use GlobalKey.currentState to save or reset the form field.

See also:



Creates a DropdownButton widget that is a FormField, wrapped in an InputDecorator.


autovalidateMode AutovalidateMode
Used to enable/disable this form field auto validation and update its error text.
final, inherited
builder FormFieldBuilder<T>
Function that returns the widget representing this form field. It is passed the form field state as input, containing the current value and validation state of this field.
final, inherited
decoration InputDecoration
The decoration to show around the dropdown button form field.
enabled bool
Whether the form is able to receive user input.
final, inherited
hashCode int
The hash code for this object.
@nonVirtual, read-only, inherited
initialValue → T?
An optional value to initialize the form field to, or null otherwise.
final, inherited
key Key?
Controls how one widget replaces another widget in the tree.
final, inherited
onChanged ValueChanged<T?>?
Called when the user selects an item.
onSaved FormFieldSetter<T>?
An optional method to call with the final value when the form is saved via FormState.save.
final, inherited
restorationId String?
Restoration ID to save and restore the state of the form field.
final, inherited
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited
validator FormFieldValidator<T>?
An optional method that validates an input. Returns an error string to display if the input is invalid, or null otherwise.
final, inherited


createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
createState() FormFieldState<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 = DiagnosticLevel.info}) 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