flutter_typeahead 0.1.1

A highly customizable typeahead text input field

Flutter TypeAhead

A TypeAhead 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.

Usage examples

You can import the package with:

import 'package:flutter_typeahead/flutter_typeahead.dart';

and then use it as follows:

Example 1:

TypeAheadField(
  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 autofocus, style and decoration are the same as those of TextField, and are not mandatory.

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.

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(
          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 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.

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 field with all the usual customizations available for TextField in Flutter. Examples include: 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.

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
    )
  )

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 decoration of the suggestions box

You can also customize the decoration of the suggestions box using the suggestionsBoxDecoration parameter. For example, to give it a blue border, you can write:

suggestionsBoxDecoration: BoxDecoration(
  border: Border.all(
    color: Colors.blue
  )
)