Flutter Form Builder

This package helps in creation of data collection forms in Flutter by removing the boilerplate needed to build a form, validate fields, react to changes and collect final user input.

Also included are common ready-made form input fields for FormBuilder. This gives you a convenient way of adding common ready-made input fields instead of creating your own FormBuilderField from scratch.

---

• Features
• Inputs
  • Parameters
• Use
  • Setup
  • Basic use
  • Specific uses
    • Building your own custom field
    • Programmatically changing field value
    • Programmatically inducing an error
    • Conditional validation
    • Implement reset, clear or other button into field
• Support
  • Contribute
  • Questions and answers
  • Donations
• Roadmap
• Ecosystem
• Thanks to

Features

• Create a form with several type of inputs
• Get values from form by easy way
• Apply validators to inputs fields
• React to form fields changes and validations

Complete Form	Sign Up	Dynamic Fields	Conditional Form

Inputs

The currently supported fields include:

• FormBuilderCheckbox - Single checkbox field
• FormBuilderCheckboxGroup - List of checkboxes for multiple selection
• FormBuilderChoiceChip - Creates a chip that acts like a radio button.
• 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
• FormBuilderRadioGroup - Used to select one value from a list of Radio Widgets
• FormBuilderRangeSlider - Used to select a range from a range of values
• FormBuilderSlider - For selection of a numerical value on a slider
• FormBuilderSwitch - On/Off switch field
• FormBuilderTextField - A Material Design text field input

Parameters

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
name	String		Yes	This will form the key in the form value Map
initialValue	T	null	No	The initial value of the input field
enabled	bool	true	No	Determines whether the field widget will accept user input.
decoration	InputDecoration	InputDecoration()	No	Defines the border, labels, icons, and styles used to decorate the field.
validator	FormFieldValidator<T>	null	No	A FormFieldValidator that will check the validity of value in the FormField
onChanged	ValueChanged<T>	null	No	This event function will fire immediately the the field value changes
valueTransformer	ValueTransformer<T>	null	No	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.

Use

Setup

No specific setup required: only install the dependency and use :)

Basic use

final _formKey = GlobalKey<FormBuilderState>();

FormBuilder(
    key: _formKey,
    child:  FormBuilderTextField(
        name: 'text',
        onChanged: (val) {
            print(val); // Print the text value write into TextField
        },
    ),
)

See pub.dev example tab or github code for more details

Specific uses

Building your own custom field

To build your own field within a FormBuilder, we use FormBuilderField which will require that you define your own field. Read this article for step-by-step instructions on how to build your own custom field.

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

FormBuilderField(
  name: "name",
  validator: FormBuilderValidators.compose([
    FormBuilderValidators.required(),
  ]),
  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]);
          },
        ),
      ),
    );
  },
),

Programmatically changing field value

You can either change the value of one field at a time like so:

_formKey.currentState.fields['color_picker'].didChange(Colors.black);

Or multiple fields value like so:

_formKey.currentState.patchValue({
  'age': '50',
  'slider': 6.7,
  'filter_chip': ['Test 1'],
  'choice_chip': 'Test 2',
  'rate': 4,
  'chips_test': [
    Contact(
        'Andrew', 
        '[email protected]', 
        'https://d2gg9evh47fn9z.cloudfront.net/800px_COLOURBOX4057996.jpg',
    ),
  ],
});

Programmatically inducing an error

Using form state key or field state key

final _formKey = GlobalKey<FormBuilderState>();
final _emailFieldKey = GlobalKey<FormBuilderFieldState>();
...
FormBuilder(
  key: _formKey,
  child: Column(
    children: [
      FormBuilderTextField(
        key: _emailFieldKey,
        name: 'email',
        decoration: const InputDecoration(labelText: 'Email'),
        validator: FormBuilderValidators.compose([
          FormBuilderValidators.required(),
          FormBuilderValidators.email(),
        ]),
      ),
      ElevatedButton(
        child: const Text('Submit'),
        onPressed: () async {
          if(await checkIfEmailExists()){
            // Either invalidate using Form Key
            _formKey.currentState?.fields['email']?.invalidate('Email already taken');
            // OR invalidate using Field Key
            _emailFieldKey.currentState?.invalidate('Email already taken');
          }
        },
      ),
    ],
  ),
),

When use invalidate and validate methods, can use two optional parameters configure the behavior when invalidate field or form, like focus or auto scroll. Take a look on method documentation for more details

Using InputDecoration.errorText

Declare a variable to hold your error:

String _emailError;

Use the variable as the errorText within InputDecoration

FormBuilderTextField(
  name: 'email',
  decoration: InputDecoration(
    labelText: 'Email',
    errorText: _emailError,
  ),
  validator: FormBuilderValidators.compose([
      FormBuilderValidators.required(),
      FormBuilderValidators.email(),
  ]),
),

Set the error text

RaisedButton(
  child: Text('Submit'),
  onPressed: () async {
    setState(() => _emailError = null);
    if(await checkIfEmailExists()){
      setState(() => _emailError = 'Email already taken.');
    }
  },
),

Conditional validation

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

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

Implement reset, clear or other button into field

If you can add some button to reset specific field, can use the decoration parameter like this:

List<String> genderOptions = ['Male', 'Female', 'Other'];

FormBuilderDropdown<String>(
  name: 'gender',
  decoration: InputDecoration(
    labelText: 'Gender',
    initialValue: 'Male',
    suffix: IconButton(
      icon: const Icon(Icons.close),
      onPressed: () {
        _formKey.currentState!.fields['gender']
            ?.reset();
      },
    ),
    hintText: 'Select Gender',
  ),
  items: genderOptions
      .map((gender) => DropdownMenuItem(
            alignment: AlignmentDirectional.center,
            value: gender,
            child: Text(gender),
          ))
      .toList(),
),

Or reset value like this:

class ClearFormBuilderTextField extends StatefulWidget {
  const ClearFormBuilderTextField({super.key});

  @override
  State<ClearFormBuilderTextField> createState() =>
      _ClearFormBuilderTextFieldState();
}

class _ClearFormBuilderTextFieldState
    extends State<ClearFormBuilderTextField> {
  final ValueNotifier<String?> text = ValueNotifier<String?>(null);
  final textFieldKey = GlobalKey<FormBuilderFieldState>();

  @override
  Widget build(BuildContext context) {
    return FormBuilderTextField(
      autovalidateMode: AutovalidateMode.always,
      name: 'age',
      key: textFieldKey,
      onChanged: (value) {
        text.value = value;
      },
      decoration: InputDecoration(
        labelText: 'Age',
        suffixIcon: ValueListenableBuilder<String?>(
          valueListenable: text,
          child: IconButton(
            onPressed: () => textFieldKey.currentState?.didChange(null),
            tooltip: 'Clear',
            icon: const Icon(Icons.clear),
          ),
          builder: (context, value, child) =>
              (value?.isEmpty ?? true) ? const SizedBox() : child!,
        ),
      ),
    );
  }
}

Support

Contribute

You have some ways to contribute to this packages

• Beginner: Reporting bugs or request new features
• Intermediate: Implement new features (from issues or not) and created pull requests
• Advanced: Join to organization like a member and help coding, manage issues, dicuss new features and other things

See contribution file for more details

Questions and answers

You can question or search answers on Github discussion or on StackOverflow

Donations

Donate or become a sponsor of Flutter Form Builder Ecosystem

Roadmap

• Solve open issues, prioritizing bugs

Ecosystem

Take a look to our awesome ecosystem and all packages in there

Thanks to

All contributors