The flutter_midi_pro plugin provides functions for loading SoundFont (.sf2) files and playing MIDI notes in Flutter applications. This plugin is using fluidsynth on Android, AVFoundation on iOS and MacOS to play MIDI notes. The plugin is compatible with Android, iOS and macos platforms. Windows, Linux and Web support will be added in the future using fluidsynth.
The Fluidsynth library used in Android needs to be built with CMake. Especially for flutter_midi_pro, CMake version 3.22.1 must be installed. To install CMake, check this comment: CMake Installation
To use this plugin, add flutter_midi_pro using terminal or pubspec.yaml file.
flutter pub add flutter_midi_proImport flutter_midi_pro.dart and use the MidiPro class to access the plugin's functions. MidiPro class is a singleton class, so you can use the same instance of the class in your application.
import 'package:flutter_midi_pro/flutter_midi_pro.dart';Use the loadSoundfont function to load a SoundFont file. This function returns an integer value that represents the soundfont ID. You can use this ID to load instruments from the SoundFont file and play MIDI notes.
This function loads the instrument at the given bank and program number to all channels at (0-15). If you want to load a specific instrument, you can use the selectInstrument function.
final soundfontId = await MidiPro().loadSoundfont(path: 'path/to/soundfont.sf2', bank:0, program: 0);Use the selectInstrument function to select an instrument at the given bank and program from the SoundFont file to specific channel.
await MidiPro().selectInstrument(sfId: soundfontId, channel: 0, bank: 0, program: 0);Use the playMidiNote function to play a MIDI note with a given MIDI value and velocity. The MIDI value is the MIDI number of the note you want to play (0-127). The velocity is the volume of the note (0-127).
midiPro.playNote(sfId: soundfontId, channel: 0, key: 60, velocity: 127);Use the stopMidiNote function to stop a MIDI note with a given MIDI number. This function stops the note on specific channel.
midiPro.stopNote(sfId: soundfontId, channel: 0, key: 60);Here's an example of how you could use the flutter_midi_pro plugin to play a piano using a SoundFont file and using the flutter_piano_pro:
import 'package:flutter/material.dart';
import 'package:flutter_midi_pro/flutter_midi_pro.dart';
import 'package:flutter_piano_pro/flutter_piano_pro.dart';
import 'package:flutter_piano_pro/note_model.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatefulWidget {
const MyApp({super.key});
@override
State<MyApp> createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
final MidiPro midiPro = MidiPro();
final ValueNotifier<Map<int, String>> loadedSoundfonts = ValueNotifier<Map<int, String>>({});
final ValueNotifier<int?> selectedSfId = ValueNotifier<int?>(null);
final instrumentIndex = ValueNotifier<int>(0);
final bankIndex = ValueNotifier<int>(0);
final channelIndex = ValueNotifier<int>(0);
final volume = ValueNotifier<int>(127);
Map<int, NoteModel> pointerAndNote = {};
/// Loads a soundfont file from the specified path.
/// Returns the soundfont ID.
Future<int> loadSoundfont(String path, int bank, int program) async {
if (loadedSoundfonts.value.containsValue(path)) {
print('Soundfont file: $path already loaded. Returning ID.');
return loadedSoundfonts.value.entries.firstWhere((element) => element.value == path).key;
}
final int sfId = await midiPro.loadSoundfont(path: path, bank: bank, program: program);
loadedSoundfonts.value = {sfId: path, ...loadedSoundfonts.value};
print('Loaded soundfont file: $path with ID: $sfId');
return sfId;
}
/// Selects an instrument on the specified soundfont.
Future<void> selectInstrument({
required int sfId,
required int program,
int channel = 0,
int bank = 0,
}) async {
int? sfIdValue = sfId;
if (!loadedSoundfonts.value.containsKey(sfId)) {
sfIdValue = loadedSoundfonts.value.keys.first;
} else {
selectedSfId.value = sfId;
}
print('Selected soundfont file: $sfIdValue');
await midiPro.selectInstrument(sfId: sfIdValue, channel: channel, bank: bank, program: program);
}
/// Plays a note on the specified channel.
Future<void> playNote({
required int key,
required int velocity,
int channel = 0,
int sfId = 1,
}) async {
int? sfIdValue = sfId;
if (!loadedSoundfonts.value.containsKey(sfId)) {
sfIdValue = loadedSoundfonts.value.keys.first;
}
await midiPro.playNote(channel: channel, key: key, velocity: velocity, sfId: sfIdValue);
}
/// Stops a note on the specified channel.
Future<void> stopNote({
required int key,
int channel = 0,
int sfId = 1,
}) async {
int? sfIdValue = sfId;
if (!loadedSoundfonts.value.containsKey(sfId)) {
sfIdValue = loadedSoundfonts.value.keys.first;
}
await midiPro.stopNote(channel: channel, key: key, sfId: sfIdValue);
}
/// Unloads a soundfont file.
Future<void> unloadSoundfont(int sfId) async {
await midiPro.unloadSoundfont(sfId);
loadedSoundfonts.value = {
for (final entry in loadedSoundfonts.value.entries)
if (entry.key != sfId) entry.key: entry.value
};
if (selectedSfId.value == sfId) selectedSfId.value = null;
}
final sf2Paths = ['assets/TimGM6mb.sf2', 'assets/SalC5Light2.sf2'];
@override
Widget build(BuildContext context) {
return MaterialApp(
debugShowCheckedModeBanner: false,
theme: ThemeData(
colorSchemeSeed: Colors.amber,
brightness: Brightness.dark,
),
home: Scaffold(
appBar: AppBar(
title: const Text('Flutter Midi Pro Example'),
),
body: SingleChildScrollView(
child: Column(
children: [
Column(
crossAxisAlignment: CrossAxisAlignment.center,
mainAxisSize: MainAxisSize.min,
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
const SizedBox(
height: 10,
),
FittedBox(
fit: BoxFit.scaleDown,
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: List.generate(
sf2Paths.length,
(index) => ElevatedButton(
onPressed: () => loadSoundfont(
sf2Paths[index], bankIndex.value, instrumentIndex.value),
child: Text('Load Soundfont ${sf2Paths[index]}'),
),
)),
),
const SizedBox(
height: 10,
),
ValueListenableBuilder(
valueListenable: loadedSoundfonts,
builder: (context, value, child) {
if (value.isEmpty) {
return const Text('No soundfont file loaded');
}
return Column(
children: [
const Text('Loaded Soundfont files:'),
for (final entry in value.entries)
ListTile(
title: Text(entry.value),
trailing: Row(
mainAxisSize: MainAxisSize.min,
children: [
ValueListenableBuilder(
valueListenable: selectedSfId,
builder: (context, selectedSfIdValue, child) {
return ElevatedButton(
onPressed: selectedSfIdValue == entry.key
? null
: () => selectedSfId.value = entry.key,
child: Text(selectedSfIdValue == entry.key
? 'Selected'
: 'Select'),
);
}),
ElevatedButton(
onPressed: () => unloadSoundfont(entry.key),
child: const Text('Unload'),
),
],
),
)
],
);
}),
ValueListenableBuilder(
valueListenable: selectedSfId,
builder: (context, selectedSfIdValue, child) {
return Column(
children: [
Row(
mainAxisAlignment: MainAxisAlignment.spaceEvenly,
children: [
ValueListenableBuilder(
valueListenable: bankIndex,
builder: (context, bankIndexValue, child) {
return DropdownButton<int>(
value: bankIndexValue,
items: [
for (int i = 0; i < 128; i++)
DropdownMenuItem<int>(
value: i,
child: Text(
'Bank $i',
style: const TextStyle(fontSize: 13),
),
)
],
onChanged: (int? value) {
if (value != null) {
bankIndex.value = value;
}
});
}),
ValueListenableBuilder(
valueListenable: instrumentIndex,
builder: (context, channelValue, child) {
return DropdownButton<int>(
value: channelValue,
items: [
for (int i = 0; i < 128; i++)
DropdownMenuItem<int>(
value: i,
child: Text(
'Instrument $i',
style: const TextStyle(fontSize: 13),
),
)
],
onChanged: (int? value) {
if (value != null) {
instrumentIndex.value = value;
}
});
}),
ValueListenableBuilder(
valueListenable: channelIndex,
builder: (context, channelIndexValue, child) {
return DropdownButton<int>(
value: channelIndexValue,
items: [
for (int i = 0; i < 16; i++)
DropdownMenuItem<int>(
value: i,
child: Text(
'Channel $i',
style: const TextStyle(fontSize: 13),
),
)
],
onChanged: (int? value) {
if (value != null) {
channelIndex.value = value;
}
});
}),
],
),
ValueListenableBuilder(
valueListenable: bankIndex,
builder: (context, bankIndexValue, child) {
return ValueListenableBuilder(
valueListenable: channelIndex,
builder: (context, channelIndexValue, child) {
return ValueListenableBuilder(
valueListenable: instrumentIndex,
builder: (context, instrumentIndexValue, child) {
return ElevatedButton(
onPressed: selectedSfIdValue != null
? () => selectInstrument(
sfId: selectedSfIdValue,
program: instrumentIndexValue,
bank: bankIndexValue,
channel: channelIndexValue,
)
: null,
child: Text(
'Load Instrument $instrumentIndexValue on Bank $bankIndexValue to Channel $channelIndexValue'));
});
});
}),
Padding(
padding: const EdgeInsets.all(18),
child: ValueListenableBuilder(
valueListenable: volume,
child: const Text('Volume: '),
builder: (context, value, child) {
return Row(
children: [
child!,
Expanded(
child: Slider(
value: value.toDouble(),
min: 0,
max: 127,
onChanged: selectedSfIdValue != null
? (value) => volume.value = value.toInt()
: null,
)),
const SizedBox(
width: 10,
),
Text('${volume.value}'),
],
);
})),
Padding(
padding: const EdgeInsets.all(8),
child: ElevatedButton(
onPressed: !(selectedSfIdValue != null)
? null
: () => unloadSoundfont(loadedSoundfonts.value.keys.first),
child: const Text('Unload Soundfont file'),
),
),
Stack(
children: [
PianoPro(
noteCount: 15,
onTapDown: (NoteModel? note, int tapId) {
if (note == null) return;
pointerAndNote[tapId] = note;
playNote(
key: note.midiNoteNumber,
velocity: volume.value,
channel: channelIndex.value,
sfId: selectedSfIdValue!);
debugPrint(
'DOWN: note= ${note.name + note.octave.toString() + (note.isFlat ? "♭" : '')}, tapId= $tapId');
},
onTapUpdate: (NoteModel? note, int tapId) {
if (note == null) return;
if (pointerAndNote[tapId] == note) return;
stopNote(
key: pointerAndNote[tapId]!.midiNoteNumber,
channel: channelIndex.value,
sfId: selectedSfIdValue!);
pointerAndNote[tapId] = note;
playNote(
channel: channelIndex.value,
key: note.midiNoteNumber,
velocity: volume.value,
sfId: selectedSfIdValue);
debugPrint(
'UPDATE: note= ${note.name + note.octave.toString() + (note.isFlat ? "♭" : '')}, tapId= $tapId');
},
onTapUp: (int tapId) {
stopNote(
key: pointerAndNote[tapId]!.midiNoteNumber,
channel: channelIndex.value,
sfId: selectedSfIdValue!);
pointerAndNote.remove(tapId);
debugPrint('UP: tapId= $tapId');
},
),
if (selectedSfIdValue == null)
Positioned.fill(
child: Container(
color: Colors.black.withOpacity(0.5),
child: const Center(
child: Text(
'Load Soundfont file\nMust be called before other methods',
textAlign: TextAlign.center,
),
),
),
)
],
)
],
);
}),
],
),
],
),
),
),
);
}
}
Contributions are welcome! Please feel free to submit a PR or open an issue.
- Add support for Web, Windows, and Linux.
- Add support for channel feature (MIDI Channels).
- Add controller support
- Add support for MIDI files.
If you have any questions or suggestions, feel free to contact the package maintainer, Melih Hakan Pektas, via email or through GitHub.
Thank you for contributing to flutter_piano_pro!
This project is licensed under the MIT License. See the LICENSE file for details.