Master Flutter Autocomplete: 1 Ultimate 2025 Clear Method
Tired of clunky autocomplete code? Master Flutter's Autocomplete widget with our ultimate 2025 guide. A clear, step-by-step method with advanced examples.
Alexandre Dubois
Senior Flutter Engineer passionate about creating elegant user experiences and clean code.
Picture this: your user is filling out a form, searching for a product, or entering an address. With every character they type, your app intelligently suggests possible completions. This isn't just a "nice-to-have" feature anymore; it's a cornerstone of modern, user-friendly mobile applications. Autocomplete reduces typing effort, prevents errors, and guides users towards valid inputs, dramatically improving the overall user experience.
But let's be honest, implementing a robust and polished autocomplete feature in Flutter hasn't always been straightforward. Veterans might remember manually wrestling with OverlayEntry
, Stack
widgets, and TextEditingController
listeners—a process filled with boilerplate and potential layout headaches. It worked, but it was far from elegant.
Forget all that. The game has changed. As of 2025, Flutter provides a powerful, flexible, and built-in solution that handles all the heavy lifting for you: the Autocomplete
widget. This is the one clear method you need to master. In this guide, we'll dive deep into this widget, moving from a simple implementation to advanced, real-world examples with API data. Get ready to finally conquer autocomplete, the right way.
What is Autocomplete and Why is it a UX Superpower?
At its core, autocomplete (or typeahead) is a UI pattern where the application predicts the rest of a word or phrase a user is typing. In a world of small screens and virtual keyboards, this simple interaction provides immense value:
- Speed: Users can select a suggestion faster than they can type the whole thing.
- Accuracy: It reduces typos and formatting errors, especially for complex data like addresses or product names.
- Discovery: Suggestions can introduce users to items or search terms they weren't aware of.
- Reduced Cognitive Load: Users don't have to remember exact spellings or full names. The app does the work for them.
Implementing it well signals a high-quality, thoughtful application. Implementing it poorly can be frustrating. That's why getting it right is so important.
The Old Way vs. The New: A Brief History
Before the official Autocomplete
widget, developers had to build this functionality from scratch. The typical approach involved:
- A
TextField
to capture user input. - A listener on the
TextEditingController
to react to changes. - An
OverlayEntry
to display a floating list of suggestions. - Complex calculations with a
CompositedTransformFollower
to position the overlay correctly. - Manually managing the state of the overlay (showing/hiding it).
This was tedious, error-prone, and required a lot of boilerplate code. Thankfully, the Flutter team recognized this pain point and gave us a much better way.
The Autocomplete
Widget: Your New Best Friend
The built-in Autocomplete
widget is a composable, highly configurable widget that abstracts away all the complexity of managing overlays and state. It's built on a foundation of four key properties:
Property | Role |
---|---|
optionsBuilder |
The brain. This function is called whenever the user types. It takes the current text and must return a list of potential options to display. |
onSelected |
The action. This callback fires when the user selects an option from the list. This is where you handle the chosen value. |
optionsViewBuilder |
The looks. This function builds the widget that displays the list of options (e.g., a styled ListView ). |
fieldViewBuilder |
The input. This optional function builds the text field itself, giving you full control over its appearance and behavior. |
By providing implementations for these builders, you can create nearly any autocomplete experience you can imagine.
The Ultimate Method: A Step-by-Step Implementation
Let's build a practical example. We'll create an autocomplete field for a list of programming languages. This is the 2025 standard method.
Step 1: The Basic Widget Structure
First, let's define our data source. In a real app, this might come from a database or API, but for now, a simple static list will do.
// In your State or StatefulWidget
static const List<String> _kOptions = <String>[
'Flutter',
'Dart',
'Python',
'JavaScript',
'Java',
'Kotlin',
'Swift',
'Go',
'Rust',
];
Step 2: The `optionsBuilder` - Your Filtering Logic
This is where the magic happens. The optionsBuilder
receives the current TextEditingValue
and returns an Iterable
of matching options. Our logic will be simple: if the text is empty, return an empty list. Otherwise, return all options that contain the typed text (case-insensitive).
Autocomplete<String>(
optionsBuilder: (TextEditingValue textEditingValue) {
if (textEditingValue.text == '') {
return const Iterable<String>.empty();
}
return _kOptions.where((String option) {
return option.toLowerCase().contains(textEditingValue.text.toLowerCase());
});
},
// ... other properties will be added next
);
Step 3: Handling Selection with `onSelected`
When the user taps an option, onSelected
is called with the chosen value. You can then use this value to update your state, submit a form, or navigate to a new screen. Here, we'll just print it to the console.
Autocomplete<String>(
// ... optionsBuilder from before
onSelected: (String selection) {
debugPrint('You just selected $selection');
},
);
At this point, you have a fully functional autocomplete widget! It uses a default TextField
and a default ListView
. But we can make it look much better.
Step 4: Customizing the Look with `optionsViewBuilder`
The default options view is plain. Let's create a more polished list with some elevation and proper material design. The optionsViewBuilder
gives us the `context`, the `onSelected` callback, and the `options` to display.
Autocomplete<String>(
// ... optionsBuilder and onSelected from before
optionsViewBuilder: (BuildContext context, AutocompleteOnSelected<String> onSelected, Iterable<String> options) {
return Align(
alignment: Alignment.topLeft,
child: Material(
elevation: 4.0,
child: SizedBox(
height: 200.0, // Constrain the height of the options list
child: ListView.builder(
padding: EdgeInsets.zero,
itemCount: options.length,
itemBuilder: (BuildContext context, int index) {
final String option = options.elementAt(index);
return InkWell(
onTap: () {
onSelected(option);
},
child: Padding(
padding: const EdgeInsets.all(16.0),
child: Text(option),
),
);
},
),
),
),
);
},
);
By wrapping our ListView
in an Align
and Material
widget, we get a properly positioned, floating list with a shadow, just like users expect. We've now replicated and improved upon the "old way" with a fraction of the code.
Level Up: Advanced Autocomplete Techniques
A static list is good for learning, but real-world apps often need more power. Let's explore some advanced use cases.
Fetching Suggestions from an API
Most of the time, your data will come from a server. The Autocomplete
widget handles asynchronous operations beautifully. The optionsBuilder
can be an async
function and return a Future<Iterable<T>>
.
Let's simulate an API call that searches for user data. Note the use of Future.delayed
to mimic network latency.
// A mock API call
Future<Iterable<String>> _fetchApiData(String query) async {
await Future.delayed(const Duration(milliseconds: 500)); // Simulate network delay
if (query.isEmpty) {
return const Iterable<String>.empty();
}
// In a real app, you'd make an http request here
final List<String> allUsers = ['Alice', 'Bob', 'Charlie', 'David', 'Eve'];
return allUsers.where((user) => user.toLowerCase().contains(query.toLowerCase()));
}
// In your widget build method:
Autocomplete<String>(
// The optionsBuilder is now async!
optionsBuilder: (TextEditingValue textEditingValue) async {
return await _fetchApiData(textEditingValue.text);
},
onSelected: (String selection) {
debugPrint('You selected user: $selection');
},
);
Pro Tip: In a production app, you should "debounce" your API calls. This means waiting for the user to stop typing for a brief moment (e.g., 300ms) before firing the network request. This prevents sending a request for every single keystroke and saves resources. You can achieve this using packages like flutter_hooks
or a simple Timer
.
Adding a Polished Loading Indicator
When fetching data from an API, the UI should provide feedback. The Autocomplete
widget doesn't have a built-in loading state, but we can easily add one using a FutureBuilder
inside our optionsViewBuilder
. However, a simpler and more elegant approach is to use the fact that the `optionsBuilder` is re-run. While a new `Future` is running, the old data is still available!
A clever trick is to use a CircularProgressIndicator
as one of the list items if the data is currently being fetched. Flutter's `Autocomplete` widget is smart. When you pass an `async` function to `optionsBuilder`, the builder is re-run with a `Future`. The `optionsViewBuilder` is then built using a `FutureBuilder` internally. We can leverage this to show a loading state within our custom view.
A more direct way is to manage the loading state yourself and show a loading indicator in the optionsViewBuilder
while waiting for the results. Let's see how that looks inside the `optionsViewBuilder` using a `FutureBuilder` directly for clarity:
// This example is more conceptual to show the loading state.
// The Autocomplete widget already uses a FutureBuilder internally.
// So you can build your UI based on the connection state.
// Let's modify the optionsViewBuilder to show a loader
optionsViewBuilder: (context, onSelected, options) {
// While waiting for the async optionsBuilder to complete,
// the 'options' might be the previous result.
// A common pattern is to show a loader in the text field itself.
// We will do that in the next section.
// For the options view, let's keep it simple for now.
// The internal FutureBuilder handles this, but if you want custom logic:
if (/* _isLoading */ false) { // Assuming you manage a _isLoading state
return const Center(child: CircularProgressIndicator());
}
return Align(
// ... your Material and ListView from before
);
}
The cleanest approach is often to show the loading indicator within the text field itself, which we can do with our final advanced technique.
Creating a Custom Input Field with `fieldViewBuilder`
You are not limited to the default text field. The fieldViewBuilder
gives you complete control. It provides a TextEditingController
, a FocusNode
, and a callback to handle form submission. You can use these to build any input widget you want.
Let's create a decorated TextField
with an icon and a loading indicator.
// Assume you have a _isLoading boolean in your state
Autocomplete<String>(
// ... optionsBuilder and onSelected
fieldViewBuilder: (BuildContext context, TextEditingController fieldTextEditingController, FocusNode fieldFocusNode, VoidCallback onFieldSubmitted) {
return TextField(
controller: fieldTextEditingController,
focusNode: fieldFocusNode,
decoration: InputDecoration(
hintText: 'Search for a user...',
border: const OutlineInputBorder(),
prefixIcon: const Icon(Icons.search),
suffixIcon: _isLoading
? const SizedBox(
width: 20,
height: 20,
child: Center(child: CircularProgressIndicator(strokeWidth: 2.0)),
)
: null,
),
);
},
);
To make this work, you'd need to wrap your Autocomplete
in a StatefulWidget
, manage an `_isLoading` flag, and call `setState` before and after your API call in `optionsBuilder`. This gives you a seamless, professional-looking search experience.
Common Pitfalls and Best Practices
- Not Debouncing API Calls: As mentioned, hitting your API on every keystroke is inefficient. Always debounce network requests.
- Ignoring Keyboard and Focus: Ensure the keyboard dismisses correctly when an item is selected or the user taps outside the field. The `Autocomplete` widget handles much of this, but be mindful when customizing with
fieldViewBuilder
. - Poor Empty/Error States: What happens if the API fails or returns no results? Your
optionsViewBuilder
should handle these cases gracefully, perhaps showing a message like "No results found" or "Error loading data." - Accessibility: Use semantic widgets and ensure your custom views are accessible. The default implementation has good accessibility support, so try not to break it.
Conclusion: You've Mastered Autocomplete!
You've seen how Flutter's Autocomplete
widget transforms a once-complex task into a manageable and enjoyable one. By understanding its core components—optionsBuilder
, onSelected
, optionsViewBuilder
, and fieldViewBuilder
—you have a clear and powerful pattern for building predictive text input.
From simple local lists to dynamic, API-driven suggestions with custom UIs, this single widget provides all the tools you need. This is the ultimate, modern method for implementing autocomplete in Flutter. Now go ahead and build some amazing, intuitive user experiences!