FormField<T> class

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.
Implemented by


FormField({Key key, @required 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
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. [...]
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 toStringDeep. [...]
toString({DiagnosticLevel minLevel: DiagnosticLevel.debug }) → String
Returns 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 ==(dynamic other) → bool
The equality operator. [...]