Form class Null safety

An optional container for grouping together multiple form field widgets (e.g. TextField widgets).

Each individual form field should be wrapped in a FormField widget, with the Form widget as a common ancestor of all of those. Call methods on FormState to save, reset, or validate each FormField that is a descendant of this Form. To obtain the FormState, you may use Form.of with a context whose ancestor is the Form, or pass a GlobalKey to the Form constructor and call GlobalKey.currentState.

This example shows a Form with one TextFormField to enter an email address and an ElevatedButton to submit the form. A GlobalKey is used here to identify the Form and validate input.

To create a local project with this code sample, run:
flutter create --sample=widgets.Form.1 mysample

See also:

Inheritance

Constructors

Form({Key? key, required Widget child, WillPopCallback? onWillPop, VoidCallback? onChanged, AutovalidateMode? autovalidateMode})
Creates a container for form fields.
const

Properties

autovalidateMode AutovalidateMode
Used to enable/disable form fields auto validation and update their error text.
final
child Widget
The widget below this widget in the tree.
final
hashCode int
The hash code for this object.
@nonVirtual, read-only, inherited
key Key?
Controls how one widget replaces another widget in the tree.
final, inherited
onChanged VoidCallback?
Called when one of the form fields changes.
final
onWillPop WillPopCallback?
Enables the form to veto attempts by the user to dismiss the ModalRoute that contains the form.
final
runtimeType Type
A representation of the runtime type of the object.
read-only, inherited

Methods

createElement() StatefulElement
Creates a StatefulElement to manage this widget's location in the tree.
inherited
createState() FormState
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, inherited
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, inherited

Static Methods

of(BuildContext context) FormState?
Returns the closest FormState which encloses the given context.