Form class

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 a RaisedButton to submit the form. A GlobalKey is used here to identify the Form and validate input.

final _formKey = GlobalKey<FormState>();

Widget build(BuildContext context) {
  return Form(
    key: _formKey,
    child: Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
          decoration: const InputDecoration(
            hintText: 'Enter your email',
          validator: (value) {
            if (value.isEmpty) {
              return 'Please enter some text';
            return null;
          padding: const EdgeInsets.symmetric(vertical: 16.0),
          child: RaisedButton(
            onPressed: () {
              // Validate will return true if the form is valid, or false if
              // the form is invalid.
              if (_formKey.currentState.validate()) {
                // Process data.
            child: Text('Submit'),

See also:



Form({Key key, @required Widget child, bool autovalidate: false, WillPopCallback onWillPop, VoidCallback onChanged })
Creates a container for form fields. [...]


autovalidate bool
If true, form fields will validate and update their error text immediately after every change. Otherwise, you must call FormState.validate to validate.
child Widget
The widget below this widget in the tree. [...]
onChanged VoidCallback
Called when one of the form fields changes. [...]
onWillPop WillPopCallback
Enables the form to veto attempts by the user to dismiss the ModalRoute that contains the form. [...]
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() FormState
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 DiagnosticsNode.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. [...]

Static Methods

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