This is a simple bare-bone module which allows background playing from a HTTP stream, using ExoPlayer. It is compliant with all Android O+ requirements as foreground services are concerned.

• One hundred percent Kotlin.
• Uses foreground service to ensure playback is preserved when in background.
• Uses audio focus wrapping, to perform handling of audio focus in Android O+ style.
• Shows an ongoing notification for the user to control playback, using PlayerNotificationManager from ExoPlayer.
• It is completely decoupled from whichever implementation any users wants for the player activity.
• This is untested.

• Set up a main app project as usual
• Clone into a separate folder from the main project
• Use Import module... function from AS
• Go to Project structure and add playerlib as a dependency

An activity which launches the service, and a broadcast receiver to handle the launch of the activity from the player notification (when it gets clicked). It is possible to launch the stream with a custom url to the stream.

AndroidManifest.xml

<application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        tools:ignore="GoogleAppIndexingWarning">
        <activity
            android:name="com.beraldo.myapp.PlayerActivity"
            android:configChanges="keyboard|keyboardHidden|orientation|screenSize|screenLayout|smallestScreenSize|uiMode"
            android:label="PlayerActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <service android:name="com.beraldo.playerlib.PlayerService" />

        <receiver
            android:name=".LaunchPlayerBroadcastReceiver"
            android:exported="true">
            <intent-filter>
                <action android:name="com.beraldo.playerlib.LAUNCH_PLAYER_ACTIVITY" />
            </intent-filter>
        </receiver>
    </application>

LaunchPlayerBroadcastReceiver.kt

class LaunchPlayerBroadcastReceiver : BroadcastReceiver() {
    override fun onReceive(context: Context, intent: Intent) {
        val notifyIntent = Intent(context, PlayerActivity::class.java)
        context.startActivity(notifyIntent)
    }
}

PlayerActivity.kt

class PlayerActivity : AppCompatActivity(), AnkoLogger {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_player)

        //Start the service
        val intent = Intent(this, PlayerService::class.java).apply {
            putExtra(STREAM_URL, "http://my.stream.url")
        }
        bindService(intent, connection, Context.BIND_AUTO_CREATE)
    }

    /**
     * Create our connection to the service to be used in our bindService call.
     */
    private val connection = object : ServiceConnection {
        override fun onServiceDisconnected(name: ComponentName?) {}

        /**
         * Called after a successful bind with our PlayerService.
         */
        override fun onServiceConnected(name: ComponentName?, service: IBinder?) {
            if (service is PlayerService.PlayerServiceBinder) {
                service.getPlayerHolderInstance() // use the player and call methods on it to start and stop
            }
        }
    }
}

build.gradle of module app after importing the module (see there's implementation project(path: ':playerlib'))

[...]

android {
    [...]
}

dependencies {
    [...]
    implementation project(path: ':playerlib')
}

I took inspiration from the Google codelabs for ExoPlayer https://codelabs.developers.google.com/codelabs/exoplayer-intro/#0 and mixed it up with Architecting Video Playback through a Service https://proandroiddev.com/architecting-video-playback-through-a-service-501c7bd158fa.

I have used this lib to develop my streaming app for a web radio called RadioUci