TextFormField class Null safety

A FormField that contains a TextField.

This is a convenience widget that wraps a TextField widget in a FormField.

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<FormFieldState> (see GlobalKey) to the constructor and use GlobalKey.currentState to save or reset the form field.

When a controller is specified, its TextEditingController.text defines the initialValue. If this FormField is part of a scrolling container that lazily constructs its children, like a ListView or a CustomScrollView, then a controller should be specified. The controller's lifetime should be managed by a stateful widget ancestor of the scrolling container.

If a controller is not specified, initialValue can be used to give the automatically generated controller an initial value.

When the widget has focus, it will prevent itself from disposing via its underlying EditableText's AutomaticKeepAliveClientMixin.wantKeepAlive in order to avoid losing the selection. Removing the focus will allow it to be disposed.

Remember to call TextEditingController.dispose of the TextEditingController when it is no longer needed. This will ensure any resources used by the object are discarded.

By default, decoration will apply the ThemeData.inputDecorationTheme for the current context to the InputDecoration, see InputDecoration.applyDefaults.

For a documentation about the various parameters, see TextField.

link
Creates a TextFormField with an InputDecoration and validator function.

If the user enters valid text, the TextField appears normally without any warnings to the user

If the user enters invalid text, the error message returned from the validator function is displayed in dark red underneath the input 

TextFormField(
  decoration: const InputDecoration(
    icon: Icon(Icons.person),
    hintText: 'What do people call you?',
    labelText: 'Name *',
  ),
  onSaved: (String? value) {
    // This optional block of code can be used to run
    // code when the user saves the form.
  },
  validator: (String? value) {
    return (value != null && value.contains('@')) ? 'Do not use the @ char.' : null;
  },
)

link
This example shows how to move the focus to the next field when the user presses the SPACE key.
To create a local project with this code sample, run:
flutter create --sample=material.TextFormField.2 mysample

See also:

Inheritance

Constructors

TextFormField({Key? key, TextEditingController? controller, String? initialValue, FocusNode? focusNode, InputDecoration? decoration = const InputDecoration(), TextInputType? keyboardType, TextCapitalization textCapitalization = TextCapitalization.none, TextInputAction? textInputAction, TextStyle? style, StrutStyle? strutStyle, TextDirection? textDirection, TextAlign textAlign = TextAlign.start, TextAlignVertical? textAlignVertical, bool autofocus = false, bool readOnly = false, ToolbarOptions? toolbarOptions, bool? showCursor, String obscuringCharacter = '•', bool obscureText = false, bool autocorrect = true, SmartDashesType? smartDashesType, SmartQuotesType? smartQuotesType, bool enableSuggestions = true, MaxLengthEnforcement? maxLengthEnforcement, int? maxLines = 1, int? minLines, bool expands = false, int? maxLength, ValueChanged<String>? onChanged, GestureTapCallback? onTap, TapRegionCallback? onTapOutside, VoidCallback? onEditingComplete, ValueChanged<String>? onFieldSubmitted, FormFieldSetter<String>? onSaved, FormFieldValidator<String>? validator, List<TextInputFormatter>? inputFormatters, bool? enabled, double cursorWidth = 2.0, double? cursorHeight, Radius? cursorRadius, Color? cursorColor, Brightness? keyboardAppearance, EdgeInsets scrollPadding = const EdgeInsets.all(20.0), bool? enableInteractiveSelection, TextSelectionControls? selectionControls, InputCounterWidgetBuilder? buildCounter, ScrollPhysics? scrollPhysics, Iterable<String>? autofillHints, AutovalidateMode? autovalidateMode, ScrollController? scrollController, String? restorationId, bool enableIMEPersonalizedLearning = true, MouseCursor? mouseCursor})
Creates a FormField that contains a TextField.

Properties

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

Methods

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