text_form_field.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';

import 'input_decorator.dart';
import 'text_field.dart';
import 'theme.dart';

export 'package:flutter/services.dart' show SmartQuotesType, SmartDashesType;

/// 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] 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.
///
/// Remember to call [TextEditingController.dispose] of the [TextEditingController]
/// when it is no longer needed. This will ensure we discard any resources used
/// by the object.
///
/// 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].
///
/// {@tool snippet}
///
/// 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](https://flutter.github.io/assets-for-api-docs/assets/material/text_form_field.png)
///
/// ![If the user enters invalid text, the error message returned from the validator function is displayed in dark red underneath the input](https://flutter.github.io/assets-for-api-docs/assets/material/text_form_field_error.png)
///
/// ```dart
/// 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;
///   },
/// )
/// ```
/// {@end-tool}
///
/// {@tool dartpad --template=stateful_widget_material}
/// This example shows how to move the focus to the next field when the user
/// presses the SPACE key.
///
/// ```dart imports
/// import 'package:flutter/services.dart';
/// ```
///
/// ```dart
/// Widget build(BuildContext context) {
///   return Material(
///     child: Center(
///       child: Shortcuts(
///         shortcuts: <LogicalKeySet, Intent>{
///           // Pressing space in the field will now move to the next field.
///           LogicalKeySet(LogicalKeyboardKey.space): const NextFocusIntent(),
///         },
///         child: FocusTraversalGroup(
///           child: Form(
///             autovalidateMode: AutovalidateMode.always,
///             onChanged: () {
///               Form.of(primaryFocus!.context!)!.save();
///             },
///             child: Wrap(
///               children: List<Widget>.generate(5, (int index) {
///                 return Padding(
///                   padding: const EdgeInsets.all(8.0),
///                   child: ConstrainedBox(
///                     constraints: BoxConstraints.tight(const Size(200, 50)),
///                     child: TextFormField(
///                       onSaved: (String? value) {
///                         print('Value for field $index saved as "$value"');
///                       },
///                     ),
///                   ),
///                 );
///               }),
///             ),
///           ),
///         ),
///       ),
///     ),
///   );
/// }
/// ```
/// {@end-tool}
///
/// See also:
///
///  * <https://material.io/design/components/text-fields.html>
///  * [TextField], which is the underlying text field without the [Form]
///    integration.
///  * [InputDecorator], which shows the labels and other visual elements that
///    surround the actual text editing widget.
///  * Learn how to use a [TextEditingController] in one of our [cookbook recipes](https://flutter.dev/docs/cookbook/forms/text-field-changes#2-use-a-texteditingcontroller).
class TextFormField extends FormField<String> {
  /// Creates a [FormField] that contains a [TextField].
  ///
  /// When a [controller] is specified, [initialValue] must be null (the
  /// default). If [controller] is null, then a [TextEditingController]
  /// will be constructed automatically and its `text` will be initialized
  /// to [initialValue] or the empty string.
  ///
  /// For documentation about the various parameters, see the [TextField] class
  /// and [new TextField], the constructor.
  TextFormField({
    Key? key,
    this.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,
    @Deprecated(
      'Use autovalidateMode parameter which provide more specific '
      'behaviour related to auto validation. '
      'This feature was deprecated after v1.19.0.'
    )
    bool autovalidate = false,
    @Deprecated(
      'Use maxLengthEnforcement parameter which provides more specific '
      'behavior related to the maxLength limit. '
      'This feature was deprecated after v1.25.0-5.0.pre.'
    )
    bool maxLengthEnforced = true,
    MaxLengthEnforcement? maxLengthEnforcement,
    int? maxLines = 1,
    int? minLines,
    bool expands = false,
    int? maxLength,
    ValueChanged<String>? onChanged,
    GestureTapCallback? onTap,
    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 = true,
    TextSelectionControls? selectionControls,
    InputCounterWidgetBuilder? buildCounter,
    ScrollPhysics? scrollPhysics,
    Iterable<String>? autofillHints,
    AutovalidateMode? autovalidateMode,
    ScrollController? scrollController,
  }) : assert(initialValue == null || controller == null),
       assert(textAlign != null),
       assert(autofocus != null),
       assert(readOnly != null),
       assert(obscuringCharacter != null && obscuringCharacter.length == 1),
       assert(obscureText != null),
       assert(autocorrect != null),
       assert(enableSuggestions != null),
       assert(autovalidate != null),
       assert(
         autovalidate == false ||
         autovalidate == true && autovalidateMode == null,
         'autovalidate and autovalidateMode should not be used together.'
       ),
       assert(maxLengthEnforced != null),
       assert(
         maxLengthEnforced || maxLengthEnforcement == null,
         'maxLengthEnforced is deprecated, use only maxLengthEnforcement',
       ),
       assert(scrollPadding != null),
       assert(maxLines == null || maxLines > 0),
       assert(minLines == null || minLines > 0),
       assert(
         (maxLines == null) || (minLines == null) || (maxLines >= minLines),
         "minLines can't be greater than maxLines",
       ),
       assert(expands != null),
       assert(
         !expands || (maxLines == null && minLines == null),
         'minLines and maxLines must be null when expands is true.',
       ),
       assert(!obscureText || maxLines == 1, 'Obscured fields cannot be multiline.'),
       assert(maxLength == null || maxLength > 0),
       assert(enableInteractiveSelection != null),
       super(
       key: key,
       initialValue: controller != null ? controller.text : (initialValue ?? ''),
       onSaved: onSaved,
       validator: validator,
       enabled: enabled ?? decoration?.enabled ?? true,
       autovalidateMode: autovalidate
           ? AutovalidateMode.always
           : (autovalidateMode ?? AutovalidateMode.disabled),
       builder: (FormFieldState<String> field) {
         final _TextFormFieldState state = field as _TextFormFieldState;
         final InputDecoration effectiveDecoration = (decoration ?? const InputDecoration())
             .applyDefaults(Theme.of(field.context).inputDecorationTheme);
         void onChangedHandler(String value) {
           field.didChange(value);
           if (onChanged != null) {
             onChanged(value);
           }
         }
         return TextField(
           controller: state._effectiveController,
           focusNode: focusNode,
           decoration: effectiveDecoration.copyWith(errorText: field.errorText),
           keyboardType: keyboardType,
           textInputAction: textInputAction,
           style: style,
           strutStyle: strutStyle,
           textAlign: textAlign,
           textAlignVertical: textAlignVertical,
           textDirection: textDirection,
           textCapitalization: textCapitalization,
           autofocus: autofocus,
           toolbarOptions: toolbarOptions,
           readOnly: readOnly,
           showCursor: showCursor,
           obscuringCharacter: obscuringCharacter,
           obscureText: obscureText,
           autocorrect: autocorrect,
           smartDashesType: smartDashesType ?? (obscureText ? SmartDashesType.disabled : SmartDashesType.enabled),
           smartQuotesType: smartQuotesType ?? (obscureText ? SmartQuotesType.disabled : SmartQuotesType.enabled),
           enableSuggestions: enableSuggestions,
           maxLengthEnforced: maxLengthEnforced,
           maxLengthEnforcement: maxLengthEnforcement,
           maxLines: maxLines,
           minLines: minLines,
           expands: expands,
           maxLength: maxLength,
           onChanged: onChangedHandler,
           onTap: onTap,
           onEditingComplete: onEditingComplete,
           onSubmitted: onFieldSubmitted,
           inputFormatters: inputFormatters,
           enabled: enabled ?? decoration?.enabled ?? true,
           cursorWidth: cursorWidth,
           cursorHeight: cursorHeight,
           cursorRadius: cursorRadius,
           cursorColor: cursorColor,
           scrollPadding: scrollPadding,
           scrollPhysics: scrollPhysics,
           keyboardAppearance: keyboardAppearance,
           enableInteractiveSelection: enableInteractiveSelection,
           selectionControls: selectionControls,
           buildCounter: buildCounter,
           autofillHints: autofillHints,
           scrollController: scrollController,
         );
       },
     );

  /// Controls the text being edited.
  ///
  /// If null, this widget will create its own [TextEditingController] and
  /// initialize its [TextEditingController.text] with [initialValue].
  final TextEditingController? controller;

  @override
  _TextFormFieldState createState() => _TextFormFieldState();
}

class _TextFormFieldState extends FormFieldState<String> {
  TextEditingController? _controller;

  TextEditingController? get _effectiveController => widget.controller ?? _controller;

  @override
  TextFormField get widget => super.widget as TextFormField;

  @override
  void initState() {
    super.initState();
    if (widget.controller == null) {
      _controller = TextEditingController(text: widget.initialValue);
    } else {
      widget.controller!.addListener(_handleControllerChanged);
    }
  }

  @override
  void didUpdateWidget(TextFormField oldWidget) {
    super.didUpdateWidget(oldWidget);
    if (widget.controller != oldWidget.controller) {
      oldWidget.controller?.removeListener(_handleControllerChanged);
      widget.controller?.addListener(_handleControllerChanged);

      if (oldWidget.controller != null && widget.controller == null)
        _controller = TextEditingController.fromValue(oldWidget.controller!.value);
      if (widget.controller != null) {
        setValue(widget.controller!.text);
        if (oldWidget.controller == null)
          _controller = null;
      }
    }
  }

  @override
  void dispose() {
    widget.controller?.removeListener(_handleControllerChanged);
    super.dispose();
  }

  @override
  void didChange(String? value) {
    super.didChange(value);

    if (_effectiveController!.text != value)
      _effectiveController!.text = value ?? '';
  }

  @override
  void reset() {
    // setState will be called in the superclass, so even though state is being
    // manipulated, no setState call is needed here.
    _effectiveController!.text = widget.initialValue ?? '';
    super.reset();
  }

  void _handleControllerChanged() {
    // Suppress changes that originated from within this class.
    //
    // In the case where a controller has been passed in to this widget, we
    // register this change listener. In these cases, we'll also receive change
    // notifications for changes originating from within this class -- for
    // example, the reset() method. In such cases, the FormField value will
    // already have been set.
    if (_effectiveController!.text != value)
      didChange(_effectiveController!.text);
  }
}