Flutter Examples

This directory contains Flutter examples for sherpa-onnx.

Start here: Read hello_world first to learn how to initialize sherpa-onnx in a Flutter app. Then read vad-from-microphone or vad-from-file to learn how to copy model files from assets to a writable directory — this is required for all examples that use models.

Examples

Initialization

All Flutter examples initialize sherpa-onnx the same way:

import 'package:sherpa_onnx/sherpa_onnx.dart' as sherpa_onnx;

await sherpa_onnx.initBindingsAsync();

No path argument is needed. The native library is linked into the app bundle by the Flutter build system.

Isolates: Each isolate has its own FFI binding state. You must call initBindings() or initBindingsAsync() in every isolate that uses sherpa-onnx APIs. Calling it in one isolate does NOT make sherpa-onnx available in other isolates. See the vad-from-microphone example for a working isolate pattern.

Model files

Flutter apps run in a sandbox and cannot access arbitrary file paths. Model files must be bundled as Flutter assets and copied to a writable directory at runtime.

Step 1: Add the model to pubspec.yaml:

flutter:
  assets:
    - assets/model.onnx

Step 2: Copy the model to a writable directory:

import 'dart:io';
import 'package:flutter/services.dart' show rootBundle;
import 'package:path_provider/path_provider.dart';

Future<String> copyAsset(String assetPath, String fileName) async {
  final dir = await getApplicationDocumentsDirectory();
  final file = File('${dir.path}/$fileName');
  if (!await file.exists()) {
    final data = await rootBundle.load(assetPath);
    await file.writeAsBytes(data.buffer.asUint8List());
  }
  return file.path;
}

Step 3: Use the copied path in your config:

final modelPath = await copyAsset('assets/model.onnx', 'model.onnx');

See vad-from-microphone or vad-from-file for complete working examples.

Running on different platforms

macOS

cd hello_world
flutter pub get
flutter run -d macos

iOS

Connect your iPhone, then:

flutter run -d <device-id>

You need a valid Apple Developer certificate for device deployment. For iOS apps that use the microphone, add NSMicrophoneUsageDescription to ios/Runner/Info.plist.

Android

flutter run -d <device-id>

If you get a minSdk error, update android/app/build.gradle:

android {
    defaultConfig {
        minSdk = 23
    }
}

Linux

flutter config --enable-linux-desktop
flutter run -d linux

Windows

flutter run -d windows

Web

flutter run -d chrome

Pre-built apps

Download pre-built Flutter apps for different platforms at https://github.com/k2-fsa/sherpa-onnx/releases/tag/flutter

Web demos

Try the following demos directly in your browser: