Manage calls using the Telecom API

This guide covers how to route audio for Bluetooth devices using the Telecom API and set the connection for VoIP calls. Read the Build a calling app guide before continuing.

By using the ConnectionService and Connection classes, you can access the audio state and a list of available Bluetooth devices, and can route audio to a selected Bluetooth device.

VoIP Connection and ConnectionService

Create a VoIPConnection class that extends from Connection. This class controls the state of the current call. As the Build a calling app guide states, make this a self-managed application and set the audio mode for a VoIP application.

Kotlin

class VoIPConnection : Connection() {
  init {
    setConnectionProperties(PROPERTY_SELF_MANAGED)
    setAudioModeIsVoip(true)
  }
}

Java

public class VoIPConnection extends Connection {
  public VoIPConnection() {
    setConnectionProperties(PROPERTY_SELF_MANAGED);
    setAudioModeIsVoip(true);
  }
}

Next, return an instance of this class in ConnectionService when an incoming or outgoing call occurs.

Kotlin

class VoIPConnectionService : ConnectionService() {
  override fun onCreateOutgoingConnection(
    connectionManagerPhoneAccount: PhoneAccountHandle,
    request: ConnectionRequest,
  ): Connection {
    return VoIPConnection()
  }
}

Java

public class VoIPConnectionService extends ConnectionService {
  @Override
  public Connection onCreateOutgoingConnection(PhoneAccountHandle connectionManagerPhoneAccount, ConnectionRequest request) {
    return new VoIPConnection();
  }
}

Ensure the manifest correctly points to the VoIPConnectionService class.

With these custom Connection and ConnectionService classes, you can control which device and what type of audio routing you wish to use during a call.

Get the current audio state

To get the current audio state, call getCallAudioState(). getCallAudioState() returns if the device is streaming using Bluetooth, Earpiece, Wired, or Speaker.

mAudioState = connection.getCallAudioState()

On State Changed

Subscribe to changes in CallAudioState by overriding onCallAudioStateChanged(). This alerts you of any changes to the state.

Kotlin

fun onCallAudioStateChanged(audioState: CallAudioState) {
  mAudioState = audioState
}

Java

@Override
public void onCallAudioStateChanged(CallAudioState audioState) {
  mAudioState = audioState;
}

Get the current device

Get the current active device using CallAudioState.getActiveBluetoothDevice(). This function returns the active Bluetooth device.

Kotlin

val activeDevice: BluetoothDevice = mAudioState.getActiveBluetoothDevice()

Java

BluetoothDevice activeDevice = mAudioState.getActiveBluetoothDevice();

Get Bluetooth devices

Get a list of Bluetooth devices that are available for call audio routing using CallAudioState.getSupportedBluetoothDevices().

Kotlin

val availableBluetoothDevices: Collection =
  mAudioState.getSupportedBluetoothDevices()

Java

Collection availableBluetoothDevices = mAudioState.getSupportedBluetoothDevices();

Route the call audio

Route the call audio to an available Bluetooth device using requestBluetoothAudio(BluetoothDevice):

requestBluetoothAudio(availableBluetoothDevices[0]);

Using API level 23 and higher

Enable ROUTE_BLUETOOTH without specifying the device using setAudioRoute(int). This defaults routing to current, active bluetooth devices on Android 9 and higher.

setAudioRoute(CallAudioState.ROUTE_BLUETOOTH);