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.
Implemented by


FormField({Key key, FormFieldBuilder<T> builder, FormFieldSetter<T> onSaved, FormFieldValidator<T> validator, T initialValue, bool autovalidate: false })

Creates a single form field.



autovalidate bool

If true, this form field will validate and update its error text immediately after every change. Otherwise, you must call FormFieldState.validate to validate. If part of a Form that autovalidates, this value will be ignored.

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.

initialValue → T

An optional value to initialize the form field to, or null otherwise.

onSaved FormFieldSetter<T>

An optional method to call with the final value when the form is saved via Form.save().

validator FormFieldValidator<T>

An optional method that validates an input. Returns an error string to display if the input is invalid, or null otherwise.

hashCode int

The hash code for this object.

read-only, inherited
key Key

Controls how one widget replaces another widget in the tree.

final, inherited
runtimeType Type

A representation of the runtime type of the object.

read-only, inherited


createState() FormFieldState<T>

Creates the mutable state for this widget at a given location in the tree.

createElement() StatefulElement

Creates a StatefulElement to manage this widget's location in the tree.

debugFillDescription(List<String> description) → void

Add additional information to the given description for use by toString.

@mustCallSuper, @protected, inherited
noSuchMethod(Invocation invocation) → dynamic

Invoked when a non-existent method or property is accessed.

toString() String

Returns a string representation of this object.

toStringShort() String

A short, textual description of this widget.



operator ==(other) bool

The equality operator.