How do you change the audio output device in flutter?
Flutter is an open-source mobile application development framework created by Google. It allows developers to build native-quality iOS and Android apps from a single codebase. Out of the box, Flutter provides basic capabilities for playing audio, including effects for control, speed, and pitch. However, for more advanced use cases like background audio, audio streams, or manipulating multiple audio players, additional plugins are required.
Popular Flutter audio plugins include audioplayers and just_audio. These provide more configurable audio players that work across platforms. With the right setup, Flutter apps can leverage the full native audio capabilities of the device.
This guide will cover the key concepts and best practices for working with audio in Flutter, including changing the audio output device, persisting selections, handling interrupts, and platform-specific considerations.
Default Audio Behavior
Flutter applications play audio through the default audio output device by default. This means that audio will be routed to the built-in speaker or earpiece on a mobile device, or speakers connected to a desktop or laptop computer, without any additional configuration.
The Flutter audio plugins like audioplayers and just_audio are designed to seamlessly leverage the platform’s native audio APIs and behavior. So on Android, they will play audio through the device’s default audio output, and on iOS through the receiver.
This default behavior is convenient in most cases. However, sometimes developers may want more control over audio routing. For example, a calling or video chat app would need to be able to switch between the speaker and receiver for a better user experience. Or a media app may want to allow the user to select different audio outputs such as headphones or wireless speakers.
Flutter provides capabilities to override the default audio behavior by configuring audio sessions. This allows developers to take control of audio routing between different outputs like the speaker, receiver, headphones, HDMI, etc.
Getting the Available Audio Devices
To get a list of available audio output devices, you can use the audioplayers plugin which provides access to the audio devices on Android and iOS. This works by calling the audioplayers AudioCache.getAudioDevice() method which returns a list of available audio devices.
For example:
List devices = await AudioCache.getAudioDevice();
for(var device in devices) {
print(device.name);
}
This will print out the name of each available audio device. You can then use this list to allow the user to select which device they want to use for audio output in your Flutter app.
The AudioDevice class contains properties like name, id etc that you can use to display the device names and IDs in a UI picker for example. This provides a handy way to get the audio devices list in Flutter.
Selecting an Audio Output Device
In Flutter, you can select a specific audio output device to use for playing audio using the audioplayers plugin. The audioplayers plugin provides an AudioPlayer class that allows setting the audio output device.
To select an audio output device, first get a list of available devices using the getAudioOutputs() method on AudioPlayer. This returns a list of AudioOutputDevices.
You can then pass the desired AudioOutputDevice to the setAudioOutput() method to set it as the active output device for that AudioPlayer instance. For example:
final players = AudioPlayer(); final outputDevices = await players.getAudioOutputs(); players.setAudioOutput(outputDevices[0]);
This will set the first available audio output device returned by getAudioOutputs() as the active output for the players instance. All audio played through this instance will now use that device.
You need to call setAudioOutput() whenever you want to change the active output device. Calling it again with a different device will switch the output.
So in summary, use getAudioOutputs() and setAudioOutput() on audioplayers AudioPlayer to select specific audio output devices for playback in Flutter.
References: https://pub.dev/packages/flutter_audio_output
Persisting the Audio Output Selection
Once the user has selected their preferred audio output device, you’ll likely want to persist that selection so it remains the default across app restarts and session changes. Here are a few approaches for persisting the audio output device:
Flutter provides the shared_preferences plugin which offers a simple data persistence solution using key-value pairs. When the user selects a device, you can save it with a key like “selectedAudioDevice” and the device ID as the value. Then on app start, check for that value and default to it if present.
For more robust data persistence, you may want to use SQLite via the sqflite plugin. Save the device ID along with additional metadata like the selection timestamp. This allows retrieving the most recently used device.
On Android, you can use SharedPreferences to persist the device ID. On iOS, look into storing the preferred device in UserDefaults.
Overall, leveraging a simple persistent key-value storage system is recommended for persisting the user’s audio device selection in a Flutter app.
Testing the Audio Output
Once you have selected a new audio output device, it’s important to test that audio is actually routing to that device as expected. Here is an example of how to play a simple audio file to test the selected output:
First, load an audio file such as an MP3 into memory using the audioplayers package:
import 'package:audioplayers/audioplayers.dart';
final player = AudioPlayer();
await player.setUrl('audiofile.mp3');
Then, call the play() method on the AudioPlayer instance to begin playback:
player.play();
You should hear the audio playing from the selected output device. If not, double check that you have properly requested audio focus and set the active output device. You may also try calling player.setVolume(1.0) before playback to ensure the volume is turned up.
This allows you to programatically validate that audio is routing as expected after changing outputs. Handle any errors or lack of audio gracefully to provide a good user experience.
For more examples, see the audioplayers package documentation and audio_service for background audio testing.
Handling Device Changes
Your app should properly handle when the available audio output devices change while the app is running. This can happen if the user plugs in headphones, connects to a Bluetooth audio device, or plugs their phone into an external speaker.
You can listen for changes to the available audio devices by subscribing to the onAudioManagerDevicesChanged stream provided by the audio_session plugin:
audioSession.onAudioManagerDevicesChanged.listen((devices) {
// Handle device changes
});
Within this callback, you can call audioSession.setActive(true) to re-activate the audio session which will route audio to the newly selected default device.
Alternatively, you can retrieve the current list of available devices using audioSession.availableAudioDevices and select a specific device to switch the audio routing to that device. This allows persisting a user’s chosen audio device even if other devices become available.
Properly handling device changes ensures your audio keeps playing smoothly even as the user’s environment changes during use of your app.
Audio Session Management
Properly managing the audio session is crucial for a high quality audio experience in Flutter apps. The audio_session package provides functionality to set the audio session category and handle audio focus and mixing behaviors on iOS and Android.
On iOS, it allows setting the AVAudioSession category, mode, policy options like Bluetooth options, etc. On Android, it lets you set audio attributes like usage, content type, flags, etc. It also handles audio focus requests, interruptions, and mixing behaviors.
Another useful package is audio_service which enables background audio playback and media button controls. It manages the audio session while the UI is in the foreground or background.
Properly configuring and managing the audio session is key for features like background audio, routing audio to different outputs like Bluetooth, handling interruptions gracefully, and adjusting audio levels.
Platform Differences
There are some key differences in how iOS and Android handle audio that are important to consider when building a cross-platform audio app with Flutter:
On iOS, apps need to set a specific audio session category in order to play audio. The most common categories are playback for music/media playback apps, and playAndRecord for apps like voice memos that need to play and record audio simultaneously. Android has no direct equivalent of audio sessions.
Android allows audio playback in the background by default, while iOS pauses audio playback when the app is in the background. To allow background audio on iOS, the audio background mode must be enabled in Xcode project settings.
The volume level and behavior on iOS can be controlled system-wide from the volume buttons and Control Center. On Android, apps have more control over volume levels within the app itself.
Audio focus and ducking are handled automatically by the system on iOS, while Android requires manually managing audio focus through the audio_session plugin.
Testing audio handling properly on both platforms during development is important to ensure a seamless audio experience across devices.
Conclusion
In summary, changing the audio output device in Flutter involves first getting the list of available audio devices using the audio_service plugin. You can then select the desired device and persist this selection using shared preferences. The audio_session package can help manage the active audio session across app restarts and device changes.
To test that your selected audio output device is working properly, play a simple sound and listen for the output. Make sure to handle scenarios where the active device changes or becomes unavailable while your app is running.
There are some platform differences to be aware of – Android allows selecting specific audio devices, while iOS only allows controlling the speaker or receiver output. Adjust your code accordingly to provide the best user experience.
For more details on controlling audio in Flutter apps, check out the official audio plugins documentation, as well as guides on implementing custom audio players, audio sessions, and device-specific behavior.
