Flutter MIDI通信插件flutter_midi的使用

flutter_midi 是一个用于在 iOS 和 Android 上播放 MIDI 音频的 Flutter 插件。该插件通过 SoundFont (.sf2) 文件来实现音频播放功能。

安装与配置

1. 下载 SoundFont 文件

首先，你需要下载一些 SoundFont (.sf2) 文件，例如 Piano.SF2 或 SmallTimGM6mb.sf2。

2. 更新 pubspec.yaml

将下载的 .sf2 文件存储在项目的 /assets/sf2/ 目录下，并更新 pubspec.yaml 文件以包含这些文件：

flutter:
  assets:
    - assets/sf2/Piano.SF2
    - assets/sf2/SmallTimGM6mb.sf2

3. 加载 SoundFont 文件

在应用启动时加载 SoundFont 文件以便后续播放音符。

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_midi/flutter_midi.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  [@override](/user/override)
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  [@override](/user/override)
  void initState() {
    load('assets/sf2/Piano.SF2');
    super.initState();
  }

  void load(String asset) async {
    FlutterMidi.unmute(); // Optionally Unmute
    ByteData _byte = await rootBundle.load(asset);
    FlutterMidi.prepare(sf2: _byte);
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Flutter MIDI Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                onPressed: () {
                  FlutterMidi.playMidiNote(midi: 60); // Play middle C
                },
                child: Text('Play Middle C'),
              ),
              SizedBox(height: 20),
              ElevatedButton(
                onPressed: () {
                  FlutterMidi.stopMidiNote(midi: 60); // Stop middle C
                },
                child: Text('Stop Middle C'),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

示例 Demo

以下是一个完整的示例 Demo，展示了如何加载和播放 MIDI 音符：

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter_midi/flutter_midi.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  [@override](/user/override)
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  final _flutterMidi = FlutterMidi();
  String _value = 'assets/sf2/Piano.SF2';

  [@override](/user/override)
  void initState() {
    if (!kIsWeb) {
      load(_value);
    } else {
      _flutterMidi.prepare(sf2: null);
    }
    super.initState();
  }

  void load(String asset) async {
    print('Loading File...');
    _flutterMidi.unmute();
    ByteData _byte = await rootBundle.load(asset);
    _flutterMidi.prepare(sf2: _byte, name: _value.replaceAll('assets/', ''));
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        appBar: AppBar(
          title: const Text('Plugin example app'),
        ),
        body: Center(
          child: Column(
            crossAxisAlignment: CrossAxisAlignment.center,
            mainAxisSize: MainAxisSize.min,
            mainAxisAlignment: MainAxisAlignment.center,
            children: <Widget>[
              ElevatedButton(
                child: Text('Play C'),
                onPressed: () {
                  _play(60);
                },
              ),
            ],
          ),
        ),
      ),
    );
  }

  void _play(int midi) {
    if (kIsWeb) {
      // WebMidi.play(midi);
    } else {
      _flutterMidi.playMidiNote(midi: midi);
    }
  }
}