Flutter Custom Form Builder Package - Create Full Complex Form

Now You don’t need piling up lots of widget in Flutter and codes just to create a form. The Flutter Custom Form Builder package helps you make that possible in a very efficient and flexible way with lots of other built in widgets.

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It’s a package to build Material Form with fields like TextField, DropDown, Switches, Star Rating, and many other fields etc. with the ability to create custom FormFields and composability and reuse validation functions.

Simple Usage

To use this plugin, add custom_form_builder as a dependency in your pubspec.yaml file.

import 'package:custom_form_builder/custom_form_builder.dart';

Example

final GlobalKey<FormBuilderState> _fbKey = GlobalKey<FormBuilderState>();

Note: Avoid defining the GlobalKey inside your build method because this will create a new GlobalKey on every build cycle bringing about some erratic behavior.

Note: If you use FormBuilderDateTimePicker

import 'package:intl/intl.dart';

Full Example

import 'package:flutter/material.dart';
import 'package:intl/intl.dart';
import 'package:custom_form_builder/custom_form_builder.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      home: MyHomePage(title: 'FLutterFix Custom Form'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

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

class _MyHomePageState extends State<MyHomePage> {
  final GlobalKey<FormBuilderState> _fbKey = GlobalKey<FormBuilderState>();

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: SingleChildScrollView(
              child: SafeArea(
                child: Padding(
                  padding: const EdgeInsets.all(8.0),
                  child: Center(
            child: Column(
  children: <Widget>[
    FormBuilder(
          key: _fbKey,
          initialValue: {
            'date': DateTime.now(),
            'accept_terms': false,
          },
          autovalidate: true,
          child: Column(
            children: <Widget>[
              FormBuilderDateTimePicker(
                  attribute: "date",
                  inputType: InputType.date,
                  format: DateFormat("yyyy-MM-dd"),
                  decoration:
                      InputDecoration(labelText: "Appointment Time"),
              ),
              FormBuilderSlider(
                  attribute: "slider",
                  validators: [FormBuilderValidators.min(6)],
                  min: 0.0,
                  max: 10.0,
                  initialValue: 1.0,
                  divisions: 20,
                  decoration:
                      InputDecoration(labelText: "Number of things"),
              ),
              FormBuilderCheckbox(
                  attribute: 'accept_terms',
                  label: Text(
                      "I have read and agree to the terms and conditions"),
                  validators: [
                    FormBuilderValidators.requiredTrue(
                      errorText:
                          "You must accept terms and conditions to continue",
                    ),
                  ],
              ),
              FormBuilderDropdown(
                  attribute: "gender",
                  decoration: InputDecoration(labelText: "Gender"),
                  // initialValue: 'Male',
                  hint: Text('Select Gender'),
                  validators: [FormBuilderValidators.required()],
                  items: ['Male', 'Female', 'Other']
                    .map((gender) => DropdownMenuItem(
                       value: gender,
                       child: Text("$gender")
                  )).toList(),
              ),
              FormBuilderTextField(
                  attribute: "age",
                  decoration: InputDecoration(labelText: "Age"),
                  validators: [
                    FormBuilderValidators.numeric(),
                    FormBuilderValidators.max(70),
                  ],
              ),
              FormBuilderSegmentedControl(
                  decoration:
                      InputDecoration(labelText: "Movie Rating (Archer)"),
                  attribute: "movie_rating",
                  options: List.generate(5, (i) => i + 1)
                      .map(
                          (number) => FormBuilderFieldOption(value: number))
                      .toList(),
              ),
              FormBuilderSwitch(
                  label: Text('I Accept the tems and conditions'),
                  attribute: "accept_terms_switch",
                  initialValue: true,
              ),
              FormBuilderTouchSpin(
                  decoration: InputDecoration(labelText: "Stepper"),
                  attribute: "stepper",
                  initialValue: 10,
                  step: 1,
              ),
              FormBuilderRate(
                  decoration: InputDecoration(labelText: "Rate this form"),
                  attribute: "rate",
                  iconSize: 32.0,
                  initialValue: 1.0,
                  max: 5.0,
              ),
              FormBuilderCheckboxList(
                  decoration:
                  InputDecoration(labelText: "The language of my people"),
                  attribute: "languages",
                  initialValue: ["Dart"],
                  options: [
                    FormBuilderFieldOption(value: "Dart"),
                    FormBuilderFieldOption(value: "Kotlin"),
                    FormBuilderFieldOption(value: "Java"),
                    FormBuilderFieldOption(value: "Swift"),
                    FormBuilderFieldOption(value: "Objective-C"),
                  ],
              ),
              FormBuilderChoiceChip(
                  attribute: "favorite_ice_cream",
                  options: [
                    FormBuilderFieldOption(
                      child: Text("Vanilla"),
                      value: "vanilla"
                    ),
                    FormBuilderFieldOption(
                      child: Text("Chocolate"),
                      value: "chocolate"
                    ),
                    FormBuilderFieldOption(
                      child: Text("Strawberry"),
                      value: "strawberry"
                    ),
                    FormBuilderFieldOption(
                      child: Text("Peach"),
                      value: "peach"
                    ),
                  ],
              ),
              FormBuilderFilterChip(
                    attribute: "pets",
                    options: [
                      FormBuilderFieldOption(
                        child: Text("Cats"),
                        value: "cats"
                      ),
                      FormBuilderFieldOption(
                        child: Text("Dogs"),
                        value: "dogs"
                      ),
                      FormBuilderFieldOption(
                        child: Text("Rodents"),
                        value: "rodents"
                      ),
                      FormBuilderFieldOption(
                        child: Text("Birds"),
                        value: "birds"
                      ),
                    ],
              ),
              FormBuilderSignaturePad(
                  decoration: InputDecoration(labelText: "Signature"),
                  attribute: "signature",
                  height: 100,
              ),
            ],
          ),
    ),
    Row(
          children: <Widget>[
            MaterialButton(
              child: Text("Submit"),
              onPressed: () {
                  if (_fbKey.currentState.saveAndValidate()) {
                    print(_fbKey.currentState.value);
                  }
              },
            ),
            MaterialButton(
              child: Text("Reset"),
              onPressed: () {
                  _fbKey.currentState.reset();
              },
            ),
          ],
    )
  ],
)
          ),
                ),
        ),
      ),
      // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}

Screenshots

Here’s the result from the code above

Input widgets

The currently supported fields include:

FormBuilderCheckbox – Single Checkbox field
FormBuilderCheckboxList – List of Checkboxes for multiple selection
FormBuilderChipsInput – Takes a list of Chips as input and suggests more options on typing
FormBuilderChoiceChip – Creates a chip that acts like a radio button.
FormBuilderColorPicker – For Color input selection
FormBuilderCountryPicker – Country selection from list
FormBuilderDateRangePicker – For selection of a range of dates
FormBuilderDateTimePicker – For Date, Time and DateTime input
FormBuilderDropdown – Used to select one value from a list as a Dropdown
FormBuilderFilterChip – Creates a chip that acts like a checkbox.
FormBuilderImagePicker – Picker a image from Gallery or Camera and stores it in a List of images, File or String. Note: This picker is available for iOS and Android.
FormBuilderPhoneField – International phone number input.
FormBuilderRadio – Used to select one value from a list of Radio Widgets
FormBuilderRadioGroup – Used to select one value from a list of Radio Widgets
FormBuilderRangeSlider – Used to select a range from a range of values
FormBuilderRate – For selection of a numerical value as a rating
FormBuilderSegmentedControl – For selection of a value from the CupertinoSegmentedControl as an input
FormBuilderSignaturePad – Presents a drawing pad on which user can doodle
FormBuilderSlider – For selection of a numerical value on a slider
~~FormBuilderStepper~~ – Selection of a number by tapping on a plus or minus symbol. Deprecated; replaced with FormBuilderTouchSpin
FormBuilderSwitch – On/Off switch
FormBuilderTextField – For text input. Accepts input of single-line text, multi-line text, password, email, urls etc by using different configurations and validators
FormBuilderTouchSpin – Selection of a number by tapping on a plus or minus icon
FormBuilderTypeAhead – Auto-completes user input from a list of items

In order to create an input field in the form, along with the label, and any applicable validation, there are several attributes that are supported by all types of inputs namely:

Attribute	Type	Default	Required	Description
`attribute`	`String`	`null`	`true`	This will form the key in the form value Map
`initialValue`	`dynamic`	`null`	`false`	The initial value of the input field
`readOnly`	`bool`	`false`	`false`	Determines whether the field widget will accept user input. This value will be ignored if the `readOnly` attribute of `FormBuilder` widget is set to `true`
`decoration`	`InputDecoration`	`InputDecoration()`	`false`
`validators`	`List<FormFieldValidator>`	`[]`	`false`	List of `FormFieldValidator`s that will check the validity of value candidate in the `FormField`
`onChanged`	`ValueChanged<T>`	`null`	`false`	This event function will fire immediately the the field value changes
`valueTransformer`	`ValueTransformer<T>`	`null`	`false`	Function that transforms field value before saving to form value. e.g. transform TextField value for numeric field from `String` to `num`

The rest of the attributes will be determined by the type of Widget being used.

Building your own custom field

To build your own field within a FormBuilder, we use FormBuilderCustomField which will require that you define your own FormField. The FormField will not require a validator if the validators property is already defined in the FormBuilderCustomField.

var options = ["Option 1", "Option 2", "Option 3"];

FormBuilderCustomField(
  attribute: "name",
  validators: [
    FormBuilderValidators.required(),
  ],
  formField: FormField(
    enabled: true,
    builder: (FormFieldState<dynamic> field) {
      return InputDecorator(
        decoration: InputDecoration(
          labelText: "Select option",
          contentPadding:
              EdgeInsets.only(top: 10.0, bottom: 0.0),
          border: InputBorder.none,
          errorText: field.errorText,
        ),
        child: Container(
          height: 200,
          child: CupertinoPicker(
            itemExtent: 30,
            children: options.map((c) => Text(c)).toList(),
            onSelectedItemChanged: (index) {
              field.didChange(options[index]);
            },
          ),
        ),
      );
    },
  ),
),

Validation

The validators attribute in fields take in any number of FormFieldValidator allowing composability of validation functions as well as allow reusability of already defined validator methods.

Built-in Validators

The package comes with several most common FormFieldValidators such as required, numeric, mail, URL, min, max, minLength, maxLength, IP, credit card etc. with default errorText in English but with ability to include you own error message that will display whenever validation fails.

Available built-in validators include:

FormBuilderValidators.required() – requires the field have a non-empty value.
FormBuilderValidators.numeric() – requires the field’s value to be a valid number.
FormBuilderValidators.min() – requires the field’s value to be greater than or equal to the provided number.
FormBuilderValidators.max() – requires the field’s value to be less than or equal to the provided number.
FormBuilderValidators.minLength() – requires the length of the field’s value to be greater than or equal to the provided minimum length.
FormBuilderValidators.maxLength() – requires the length of the field’s value to be less than or equal to the provided maximum length.
FormBuilderValidators.pattern() – requires the field’s value to match the provided regex pattern.
FormBuilderValidators.email() – requires the field’s value to be a valid email address.
FormBuilderValidators.url() – requires the field’s value to be a valid url.
FormBuilderValidators.IP() – requires the field’s value to be a valid IP address.
FormBuilderValidators.creditCard() – requires the field’s value to be a valid credit card number.
FormBuilderValidators.date() – requires the field’s value to be a valid date string.
FormBuilderValidators.requiredTrue() – requires the field’s value be true.

Validation example:

FormBuilderTextField(
  attribute: "age",
  decoration: InputDecoration(labelText: "Age"),
  validators: [
    FormBuilderValidators.numeric(errorText: "La edad debe ser numérica."),
    FormBuilderValidators.max(70),
  ],
),

Custom validator function

As well as the built-in validators any function of type FormFieldValidator will be accepted into the list of validators.

FormBuilderTextField(
    attribute: "over_18",
    decoration: InputDecoration(labelText: "Are you over 18?"),
    validators: [
        FormBuilderValidators.required(),
        (val){
            if(val.toLowerCase() != "yes")
                return "The answer must be Yes";
        },
    ],
),

Conditional validation

You can also validate a field based on the value of another field

FormBuilderRadio(
  decoration: InputDecoration(labelText: 'My best language'),
  attribute: "best_language",
  validators: [FormBuilderValidators.required()],
  options: [
    "Dart",
    "Kotlin",
    "Java",
    "Swift",
    "Objective-C",
    "Other"
  ]
      .map((lang) => FormBuilderFieldOption(value: lang))
      .toList(growable: false),
),
FormBuilderTextField(
    attribute: "specify",
    decoration: InputDecoration(labelText: "If Other, please specify"),
    validators: [
        (val){
            if(_fbKey.currentState.fields['best_language'].currentState.value == "Other" && (val == null || val.isEmpty))
                return "Kindly specify your language";
        },
    ],
),

Dependencies

country_pickers, date_range_picker, datetime_picker_formfield, flutter, flutter_colorpicker, flutter_touch_spin, flutter_typeahead, group_radio_button, image_picker, intl, phone_number, rating_bar, signature, validators