FormField<T> class Null safety

A single form field.

This widget maintains the current state of the form field, so that updates and validation errors are visually reflected in the UI.

When used inside a Form, you can use methods on FormState to query or manipulate the form data as a whole. For example, calling will invoke each FormField's onSaved callback in turn.

Use a GlobalKey with FormField if you want to retrieve its current state, for example if you want one form field to depend on another.

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:

  • Form, which is the widget that aggregates the form fields.
  • TextField, which is a commonly used form field for entering text.


FormField({Key? key, required FormFieldBuilder<T> builder, FormFieldSetter<T>? onSaved, FormFieldValidator<T>? validator, T? initialValue, bool enabled = true, AutovalidateMode? autovalidateMode, String? restorationId})
Creates a single form field.


autovalidateMode AutovalidateMode
Used to enable/disable this form field auto validation and update its error text.
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.
enabled bool
Whether the form is able to receive user input.
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.
key Key?
Controls how one widget replaces another widget in the tree.
final, inherited
onSaved FormFieldSetter<T>?
An optional method to call with the final value when the form is saved via
restorationId String?
Restoration ID to save and restore the state of the form field.
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.


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 =}) 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