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 FormState.save 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.
Inheritance
Implementers

Constructors

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.
const

Properties

autovalidateMode → AutovalidateMode
Used to enable/disable this form field auto validation and update its error text.
final
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
enabled → bool
Whether the form is able to receive user input.
final
hashCode → int
The hash code for this object.
nonVirtual">@nonVirtualread-onlyinherited
initialValue → T?
An optional value to initialize the form field to, or null otherwise.
final
key → Key?
Controls how one widget replaces another widget in the tree.
finalinherited
onSaved → FormFieldSetter<T>?
An optional method to call with the final value when the form is saved via FormState.save.
final
restorationId → String?
Restoration ID to save and restore the state of the form field.
final
runtimeType → Type
A representation of the runtime type of the object.
read-onlyinherited
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

Methods

createElement() → StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() → FormFieldState<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