Flutter TextFormField

gistfile1.txt

// Copyright 2015 The Chromium 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/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';


/// A [FormField] that contains a [BetterTextField].
///
/// This is a convenience widget that wraps a [BetterTextField] 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.
///
/// For a documentation about the various parameters, see [BetterTextField].
///
/// See also:
///
///  * <https://material.google.com/components/text-fields.html>
///  * [BetterTextField], 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.
class BetterTextFormField extends FormField<String> {
  /// Creates a [FormField] that contains a [BetterTextField].
  ///
  /// 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 [initalValue] or the empty string.
  ///
  /// For documentation about the various parameters, see the [BetterTextField] class
  /// and [new BetterTextField], the constructor.
  BetterTextFormField({
    Key key,
    this.controller,
    String initialValue,
    FocusNode focusNode,
    InputDecoration decoration = const InputDecoration(),
    TextInputType keyboardType = TextInputType.text,
    TextStyle style,
    TextAlign textAlign = TextAlign.start,
    bool autofocus = false,
    bool obscureText = false,
    bool autocorrect = true,
    bool autovalidate = false,
    bool maxLengthEnforced = true,
    int maxLines = 1,
    int maxLength,
    ValueChanged<String> onFieldSubmitted,
    FormFieldSetter<String> onSaved,
    FormFieldValidator<String> validator,
    List<TextInputFormatter> inputFormatters,
    bool enabled,
  }) : assert(initialValue == null || controller == null),
        assert(keyboardType != null),
        assert(textAlign != null),
        assert(autofocus != null),
        assert(obscureText != null),
        assert(autocorrect != null),
        assert(autovalidate != null),
        assert(maxLengthEnforced != null),
        assert(maxLines == null || maxLines > 0),
        assert(maxLength == null || maxLength > 0),
        super(
        key: key,
        initialValue: controller != null ? controller.text : (initialValue ?? ''),
        onSaved: onSaved,
        validator: validator,
        autovalidate: autovalidate,
        builder: (FormFieldState<String> field) {
          final _BetterTextFormFieldState state = field;
          final InputDecoration effectiveDecoration = (decoration ?? const InputDecoration())
              .applyDefaults(Theme.of(field.context).inputDecorationTheme);
          return new BetterTextField(
            controller: state._effectiveController,
            focusNode: focusNode,
            decoration: effectiveDecoration.copyWith(errorText: field.errorText),
            keyboardType: keyboardType,
            style: style,
            textAlign: textAlign,
            autofocus: autofocus,
            obscureText: obscureText,
            autocorrect: autocorrect,
            maxLengthEnforced: maxLengthEnforced,
            maxLines: maxLines,
            maxLength: maxLength,
            onChanged: field.didChange,
            onSubmitted: onFieldSubmitted,
            inputFormatters: inputFormatters,
            enabled: enabled,
          );
        },
      );

  /// 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
  _BetterTextFormFieldState createState() => new _BetterTextFormFieldState();
}

class _BetterTextFormFieldState extends FormFieldState<String> {
  TextEditingController _controller;

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

  @override
  BetterTextFormField get widget => super.widget;

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

  @override
  void didUpdateWidget(BetterTextFormField 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 = new 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 reset() {
    super.reset();
    setState(() {
      _effectiveController.text = widget.initialValue;
    });
  }

  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);
  }
}