Accurate Auto Complete Flutter Widget

Flutter TypeAhead

A TypeAhead (autocomplete) widget for Flutter, where you can show suggestions to users as they type.

Features

• Shows suggestions in an overlay that floats on top of other widgets
• Allows you to specify what the suggestions will look like through a builder function
• Allows you to specify what happens when the user taps a suggestion
• Accepts all the parameters that traditional TextFields accept, like decoration, custom TextEditingController, text styling, etc.
• Provides two versions, a normal version and a FormField version that accepts validation, submitting, etc.
• Provides high customizability; you can customize the suggestion box decoration, the loading bar, the animation, the debounce duration, etc.

Installation

See the installation instructions on pub.

Note: As for Typeahead 3.X this package is based on Dart 2.12 (null-safety). You may also want to explore the new built in Flutter 2 widgets that have similar behavior.

Usage examples

You can import the package with:

import 'package:flutter_typeahead/flutter_typeahead.dart';

For Cupertino users import:

import 'package:flutter_typeahead/cupertino_flutter_typeahead.dart';

Use it as follows:

Material Example 1:

TypeAheadField(
  textFieldConfiguration: TextFieldConfiguration(
    autofocus: true,
    style: DefaultTextStyle.of(context).style.copyWith(
      fontStyle: FontStyle.italic
    ),
    decoration: InputDecoration(
      border: OutlineInputBorder()
    )
  ),
  suggestionsCallback: (pattern) async {
    return await BackendService.getSuggestions(pattern);
  },
  itemBuilder: (context, suggestion) {
    return ListTile(
      leading: Icon(Icons.shopping_cart),
      title: Text(suggestion['name']),
      subtitle: Text('\$${suggestion['price']}'),
    );
  },
  onSuggestionSelected: (suggestion) {
    Navigator.of(context).push(MaterialPageRoute(
      builder: (context) => ProductPage(product: suggestion)
    ));
  },
)

In the code above, the textFieldConfiguration property allows us to configure the displayed TextField as we want. In this example, we are configuring the autofocus, style and decoration properties.

The suggestionsCallback is called with the search string that the user types, and is expected to return a List of data either synchronously or asynchronously. In this example, we are calling an asynchronous function called BackendService.getSuggestions which fetches the list of suggestions.

The itemBuilder is called to build a widget for each suggestion. In this example, we build a simple ListTile that shows the name and the price of the item. Please note that you shouldn’t provide an onTap callback here. The TypeAhead widget takes care of that.

The onSuggestionSelected is a callback called when the user taps a suggestion. In this example, when the user taps a suggestion, we navigate to a page that shows us the information of the tapped product.

Material Example 2:

Here’s another example, where we use the TypeAheadFormField inside a Form:

final GlobalKey<FormState> _formKey = GlobalKey<FormState>();
final TextEditingController _typeAheadController = TextEditingController();
String _selectedCity;
...
Form(
  key: this._formKey,
  child: Padding(
    padding: EdgeInsets.all(32.0),
    child: Column(
      children: <Widget>[
        Text(
          'What is your favorite city?'
        ),
        TypeAheadFormField(
          textFieldConfiguration: TextFieldConfiguration(
            controller: this._typeAheadController,
            decoration: InputDecoration(
              labelText: 'City'
            )
          ),          
          suggestionsCallback: (pattern) {
            return CitiesService.getSuggestions(pattern);
          },
          itemBuilder: (context, suggestion) {
            return ListTile(
              title: Text(suggestion),
            );
          },
          transitionBuilder: (context, suggestionsBox, controller) {
            return suggestionsBox;
          },
          onSuggestionSelected: (suggestion) {
            this._typeAheadController.text = suggestion;
          },
          validator: (value) {
            if (value.isEmpty) {
              return 'Please select a city';
            }
          },
          onSaved: (value) => this._selectedCity = value,
        ),
        SizedBox(height: 10.0,),
        RaisedButton(
          child: Text('Submit'),
          onPressed: () {
            if (this._formKey.currentState.validate()) {
              this._formKey.currentState.save();
              Scaffold.of(context).showSnackBar(SnackBar(
                content: Text('Your Favorite City is ${this._selectedCity}')
              ));
            }
          },
        )
      ],
    ),
  ),
)

Here, we assign to the controller property of the textFieldConfiguration a TextEditingController that we call _typeAheadController. We use this controller in the onSuggestionSelected callback to set the value of the TextField to the selected suggestion.

The validator callback can be used like any FormField.validator function. In our example, it checks whether a value has been entered, and displays an error message if not. The onSaved callback is used to save the value of the field to the _selectedCity member variable.

The transitionBuilder allows us to customize the animation of the suggestion box. In this example, we are returning the suggestionsBox immediately, meaning that we don’t want any animation.

Cupertino Example:

Please see the Cupertino code in the example project.

Known Issues

Animations

Placing TypeAheadField in widgets with animations may cause the suggestions box to resize incorrectly. Since animation times are variable, this has to be corrected manually at the end of the animation. You will need to add a SuggestionsBoxController described below and the following code for the AnimationController.

void Function(AnimationStatus) _statusListener;

@override
void initState() {
  super.initState();
  _statusListener = (AnimationStatus status) {
    if (status == AnimationStatus.completed ||
        status == AnimationStatus.dismissed) {
      _suggestionsBoxController.resize();
    }
  };

  _animationController.addStatusListener(_statusListener);
}

@override
  void dispose() {
    _animationController.removeStatusListener(_statusListener);
    _animationController.dispose();
    super.dispose();
}

Dialogs

There is a known issue with opening dialogs where the suggestions box will sometimes appear too small. This is a timing issue caused by the animations described above. Currently, showDialog has a duration of 150 ms for the animations. TypeAheadField has a delay of 170 ms to compensate for this. Until the end of the animation can be properly detected and fixed using the solution above, this temporary fix will work most of the time. If the suggestions box is too small, closing and reopening the keyboard will usually fix the issue.

Cupertino

The Cupertino classes in TypeAhead are still new. There are also differences in the Cupertino widgets vs the Material ones. Some behavior will not translate when moving between the two.

Customizations

TypeAhead widgets consist of a TextField and a suggestion box that shows as the user types. Both are highly customizable

Customizing the TextField

You can customize the text field using the textFieldConfiguration property. You provide this property with an instance of TextFieldConfiguration, which allows you to configure all the usual properties of TextField, like decoration, style, controller, focusNode, autofocus, enabled, etc.

Customizing the suggestions box

TypeAhead provides default configurations for the suggestions box. You can, however, override most of them. This is done by passing a SuggestionsBoxDecoration to the suggestionsBoxDecoration property.

Use the offsetX property in SuggestionsBoxDecoration to shift the suggestions box along the x-axis. You may also pass BoxConstraints to constraints in SuggestionsBoxDecoration to adjust the width and height of the suggestions box. Using the two together will allow the suggestions box to be placed almost anywhere.

Customizing the loader, the error and the “no items found” message

You can use the loadingBuilder, errorBuilder and noItemsFoundBuilder to customize their corresponding widgets. For example, to show a custom error widget:

errorBuilder: (BuildContext context, Object error) =>
  Text(
    '$error',
    style: TextStyle(
      color: Theme.of(context).errorColor
    )
  )

By default, the suggestions box will maintain the old suggestions while new suggestions are being retrieved. To show a circular progress indicator during retrieval instead, set keepSuggestionsOnLoading to false.

Hiding the suggestions box

There are three scenarios when you can hide the suggestions box.

Set hideOnLoading to true to hide the box while suggestions are being retrieved. This will also ignore the loadingBuilder. Set hideOnEmpty to true to hide the box when there are no suggestions. This will also ignore the noItemsFoundBuilder. Set hideOnError to true to hide the box when there is an error retrieving suggestions. This will also ignore the errorBuilder.

By default, the suggestions box will automatically hide when the keyboard is hidden. To change this behavior, set hideSuggestionsOnKeyboardHide to false.

Customizing the animation

You can customize the suggestion box animation through 3 parameters: the animationDuration, the animationStart, and the transitionBuilder.

The animationDuration specifies how long the animation should take, while the animationStart specified what point (between 0.0 and 1.0) the animation should start from. The transitionBuilder accepts the suggestionsBox and animationController as parameters, and should return a widget that uses the animationController to animate the display of the suggestionsBox. For example:

transitionBuilder: (context, suggestionsBox, animationController) =>
  FadeTransition(
    child: suggestionsBox,
    opacity: CurvedAnimation(
      parent: animationController,
      curve: Curves.fastOutSlowIn
    ),
  )

This uses FadeTransition to fade the suggestionsBox into the view. Note how the animationController was provided as the parent of the animation.

In order to fully remove the animation, transitionBuilder should simply return the suggestionsBox. This callback could also be used to wrap the suggestionsBox with any desired widgets, not necessarily for animation.

Customizing the debounce duration

The suggestions box does not fire for each character the user types. Instead, we wait until the user is idle for a duration of time, and then call the suggestionsCallback. The duration defaults to 300 milliseconds, but can be configured using the debounceDuration parameter.

Customizing the offset of the suggestions box

By default, the suggestions box is displayed 5 pixels below the TextField. You can change this by changing the suggestionsBoxVerticalOffset property.

Customizing the decoration of the suggestions box

You can also customize the decoration of the suggestions box using the suggestionsBoxDecoration property. For example, to remove the elevation of the suggestions box, you can write:

suggestionsBoxDecoration: SuggestionsBoxDecoration(
  elevation: 0.0
)

Customizing the growth direction of the suggestions list

By default, the list grows towards the bottom. However, you can use the direction property to customize the growth direction to be one of AxisDirection.down or AxisDirection.up, the latter of which will cause the list to grow up, where the first suggestion is at the bottom of the list, and the last suggestion is at the top.

Set autoFlipDirection to true to allow the suggestions list to automatically flip direction whenever it detects that there is not enough space for the current direction. This is useful for scenarios where the TypeAheadField is in a scrollable widget or when the developer wants to ensure the list is always viewable despite different user screen sizes.

Controlling the suggestions box

Manual control of the suggestions box can be achieved by creating an instance of SuggestionsBoxController and passing it to the suggestionsBoxController property. This will allow you to manually open, close, toggle, or resize the suggestions box.

For more information

Visit the API Documentation

GitHub

Source Code: Accurate Auto Complete Flutter Widget.