Flutter Development

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.

A

Alexandre Dubois

Senior Flutter Engineer passionate about creating elegant user experiences and clean code.

7 min read14 views

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:

  1. A TextField to capture user input.
  2. A listener on the TextEditingController to react to changes.
  3. An OverlayEntry to display a floating list of suggestions.
  4. Complex calculations with a CompositedTransformFollower to position the overlay correctly.
  5. 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.

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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!

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