Adds basic Bluetooth support to AppRTCMobile

webrtc/examples/androidapp/src/org/appspot/apprtc/AppRTCBluetoothManager.java

+/*
+ *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.appspot.apprtc;
+
+import org.appspot.apprtc.util.AppRTCUtils;
+
+import android.bluetooth.BluetoothAdapter;
+import android.bluetooth.BluetoothDevice;
+import android.bluetooth.BluetoothHeadset;
+import android.bluetooth.BluetoothProfile;
+import android.content.BroadcastReceiver;
+import android.content.Context;
+import android.content.Intent;
+import android.content.IntentFilter;
+import android.content.pm.PackageManager;
+import android.media.AudioManager;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.Process;
+import android.util.Log;
+
+import org.webrtc.ThreadUtils;
+
+import java.util.List;
+import java.util.Set;
+
+/**
+ * AppRTCProximitySensor manages functions related to Bluetoth devices in the
+ * AppRTC demo.
+ */
+public class AppRTCBluetoothManager {
+  private static final String TAG = "AppRTCBluetoothManager";
+
+  // Timeout interval for starting or stopping audio to a Bluetooth SCO device.
+  private static final int BLUETOOTH_SCO_TIMEOUT_MS = 4000;
+  // Maximum number of SCO connection attempts.
+  private static final int MAX_SCO_CONNECTION_ATTEMPTS = 2;
+
+  // Bluetooth connection state.
+  public enum State {
+    // Bluetooth is not available; no adapter or Bluetooth is off.
+    UNINITIALIZED,
+    // Bluetooth error happened when trying to start Bluetooth.
+    ERROR,
+    // Bluetooth proxy object for the Headset profile exists, but no connected headset devices,
+    // SCO is not started or disconnected.
+    HEADSET_UNAVAILABLE,
+    // Bluetooth proxy object for the Headset profile connected, connected Bluetooth headset
+    // present, but SCO is not started or disconnected.
+    HEADSET_AVAILABLE,
+    // Bluetooth audio SCO connection with remote device is closing.
+    SCO_DISCONNECTING,
+    // Bluetooth audio SCO connection with remote device is initiated.
+    SCO_CONNECTING,
+    // Bluetooth audio SCO connection with remote device is established.
+    SCO_CONNECTED
+  }
+
+  private final ThreadUtils.ThreadChecker threadChecker = new ThreadUtils.ThreadChecker();
+
+  private final Context apprtcContext;
+  private final AppRTCAudioManager apprtcAudioManager;
+  private final AudioManager audioManager;
+  private final Handler handler;
+
+  int scoConnectionAttempts;
+  private State bluetoothState;
+  private final BluetoothProfile.ServiceListener bluetoothServiceListener;
+  private BluetoothAdapter bluetoothAdapter;
+  private BluetoothHeadset bluetoothHeadset;
+  private BluetoothDevice bluetoothDevice;
+  private final BroadcastReceiver bluetoothHeadsetReceiver;
+
+  // Runs when the Bluetooth timeout expires. We use that timeout after calling
+  // startScoAudio() or stopScoAudio() because we're not guaranteed to get a
+  // callback after those calls.
+  private final Runnable bluetoothTimeoutRunnable = new Runnable() {
+    @Override
+    public void run() {
+      bluetoothTimeout();
+    }
+  };
+
+  /**
+   * Implementation of an interface that notifies BluetoothProfile IPC clients when they have been
+   * connected to or disconnected from the service.
+   */
+  private class BluetoothServiceListener implements BluetoothProfile.ServiceListener {
+    @Override
+    // Called to notify the client when the proxy object has been connected to the service.
+    // Once we have the profile proxy object, we can use it to monitor the state of the
+    // connection and perform other operations that are relevant to the headset profile.
+    public void onServiceConnected(int profile, BluetoothProfile proxy) {
+      if (profile != BluetoothProfile.HEADSET || bluetoothState == State.UNINITIALIZED) {
+        return;
+      }
+      Log.d(TAG, "BluetoothServiceListener.onServiceConnected: BT state=" + bluetoothState);
+      // Android only supports one connected Bluetooth Headset at a time.
+      bluetoothHeadset = (BluetoothHeadset) proxy;
+      updateAudioDeviceState();
+      Log.d(TAG, "onServiceConnected done: BT state=" + bluetoothState);
+    }
+
+    @Override
+    /** Notifies the client when the proxy object has been disconnected from the service. */
+    public void onServiceDisconnected(int profile) {
+      if (profile != BluetoothProfile.HEADSET || bluetoothState == State.UNINITIALIZED) {
+        return;
+      }
+      Log.d(TAG, "BluetoothServiceListener.onServiceDisconnected: BT state=" + bluetoothState);
+      stopScoAudio();
+      bluetoothHeadset = null;
+      bluetoothDevice = null;
+      bluetoothState = State.HEADSET_UNAVAILABLE;
+      updateAudioDeviceState();
+      Log.d(TAG, "onServiceDisconnected done: BT state=" + bluetoothState);
+    }
+  }
+
+  // Intent broadcast receiver which handles changes in Bluetooth device availability.
+  // Detects headset changes and Bluetooth SCO state changes.
+  private class BluetoothHeadsetBroadcastReceiver extends BroadcastReceiver {
+    @Override
+    public void onReceive(Context context, Intent intent) {
+      if (bluetoothState == State.UNINITIALIZED) {
+        return;
+      }
+      final String action = intent.getAction();
+      // Change in connection state of the Headset profile. Note that the
+      // change does not tell us anything about whether we're streaming
+      // audio to BT over SCO. Typically received when user turns on a BT
+      // headset while audio is active using another audio device.
+      if (action.equals(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED)) {
+        final int state =
+            intent.getIntExtra(BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_DISCONNECTED);
+        Log.d(TAG, "BluetoothHeadsetBroadcastReceiver.onReceive: "
+                + "a=ACTION_CONNECTION_STATE_CHANGED, "
+                + "s=" + stateToString(state) + ", "
+                + "sb=" + isInitialStickyBroadcast() + ", "
+                + "BT state: " + bluetoothState);
+        if (state == BluetoothHeadset.STATE_CONNECTED) {
+          scoConnectionAttempts = 0;
+          updateAudioDeviceState();
+        } else if (state == BluetoothHeadset.STATE_CONNECTING) {
+          // No action needed.
+        } else if (state == BluetoothHeadset.STATE_DISCONNECTING) {
+          // No action needed.
+        } else if (state == BluetoothHeadset.STATE_DISCONNECTED) {
+          // Bluetooth is probably powered off during the call.
+          stopScoAudio();
+          updateAudioDeviceState();
+        }
+        // Change in the audio (SCO) connection state of the Headset profile.
+        // Typically received after call to startScoAudio() has finalized.
+      } else if (action.equals(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED)) {
+        final int state = intent.getIntExtra(
+            BluetoothHeadset.EXTRA_STATE, BluetoothHeadset.STATE_AUDIO_DISCONNECTED);
+        Log.d(TAG, "BluetoothHeadsetBroadcastReceiver.onReceive: "
+                + "a=ACTION_AUDIO_STATE_CHANGED, "
+                + "s=" + stateToString(state) + ", "
+                + "sb=" + isInitialStickyBroadcast() + ", "
+                + "BT state: " + bluetoothState);
+        if (state == BluetoothHeadset.STATE_AUDIO_CONNECTED) {
+          cancelTimer();
+          if (bluetoothState == State.SCO_CONNECTING) {
+            Log.d(TAG, "+++ Bluetooth audio SCO is now connected");
+            bluetoothState = State.SCO_CONNECTED;
+            scoConnectionAttempts = 0;
+            updateAudioDeviceState();
+          } else {
+            Log.w(TAG, "Unexpected state BluetoothHeadset.STATE_AUDIO_CONNECTED");
+          }
+        } else if (state == BluetoothHeadset.STATE_AUDIO_CONNECTING) {
+          Log.d(TAG, "+++ Bluetooth audio SCO is now connecting...");
+        } else if (state == BluetoothHeadset.STATE_AUDIO_DISCONNECTED) {
+          Log.d(TAG, "+++ Bluetooth audio SCO is now disconnected");
+          if (isInitialStickyBroadcast()) {
+            Log.d(TAG, "Ignore STATE_AUDIO_DISCONNECTED initial sticky broadcast.");
+            return;
+          }
+          updateAudioDeviceState();
+        }
+      }
+      Log.d(TAG, "onReceive done: BT state=" + bluetoothState);
+    }
+  };
+
+  /** Construction. */
+  static AppRTCBluetoothManager create(Context context, AppRTCAudioManager audioManager) {
+    Log.d(TAG, "create" + AppRTCUtils.getThreadInfo());
+    return new AppRTCBluetoothManager(context, audioManager);
+  }
+
+  protected AppRTCBluetoothManager(Context context, AppRTCAudioManager audioManager) {
+    Log.d(TAG, "ctor");
+    ThreadUtils.checkIsOnMainThread();

[magjed_webrtc, 2016/12/10 19:34:45]

Use threadChecker.checkIsOnValidThread() instead. Or remove |threadChecker| and
use ThreadUtils.checkIsOnMainThread() everywhere instead.

[henrika_webrtc, 2016/12/12 14:13:25]

Done.

+    apprtcContext = context;
+    apprtcAudioManager = audioManager;
+    this.audioManager = getAudioManager(context);
+    bluetoothState = State.UNINITIALIZED;
+    bluetoothServiceListener = new BluetoothServiceListener();
+    bluetoothHeadsetReceiver = new BluetoothHeadsetBroadcastReceiver();
+    handler = new Handler(Looper.getMainLooper());
+  }
+
+  /** Returns the internal state. */
+  public State getState() {
+    threadChecker.checkIsOnValidThread();
+    return bluetoothState;
+  }
+
+  /**
+   * Activates components required to detect Bluetooth devices and to enable
+   * BT SCO (audio is routed via BT SCO) for the headset profile. The end
+   * state will be HEADSET_UNAVAILABLE but a state machine has started which
+   * will start a state change sequence where the final outcome depends on
+   * if/when the BT headset is enabled.
+   * Example of state change sequence when start() is called while BT device
+   * is connected and enabled:
+   *   UNINITIALIZED --> HEADSET_UNAVAILABLE --> HEADSET_AVAILABLE -->
+   *   SCO_CONNECTING --> SCO_CONNECTED <==> audio is now routed via BT SCO.
+   * Note that the AppRTCAudioManager is also involved in driving this state
+   * change.
+   */
+  public void start() {
+    threadChecker.checkIsOnValidThread();
+    Log.d(TAG, "start");
+    if (!hasPermission(apprtcContext, android.Manifest.permission.BLUETOOTH)) {
+      Log.w(TAG, "Process (pid=" + Process.myPid() + ") lacks BLUETOOTH permission");
+      return;
+    }
+    if (bluetoothState != State.UNINITIALIZED) {
+      Log.w(TAG, "Invalid BT state");
+      return;
+    }
+    bluetoothHeadset = null;
+    bluetoothDevice = null;
+    scoConnectionAttempts = 0;
+    // Get a handle to the default local Bluetooth adapter.
+    bluetoothAdapter = BluetoothAdapter.getDefaultAdapter();
+    if (bluetoothAdapter == null) {
+      Log.w(TAG, "Device does not support Bluetooth");
+      return;
+    }
+    // Ensure that the device supports use of BT SCO audio for off call use cases.
+    if (!audioManager.isBluetoothScoAvailableOffCall()) {
+      Log.e(TAG, "Bluetooth SCO audio is not available off call");
+      return;
+    }
+    logBluetoothAdapterInfo(bluetoothAdapter);
+    // Establish a connection to the HEADSET profile (includes both Bluetooth Headset and
+    // Hands-Free) proxy object and install a listener.
+    if (!getBluetoothProfileProxy(
+            apprtcContext, bluetoothServiceListener, BluetoothProfile.HEADSET)) {
+      Log.e(TAG, "BluetoothAdapter.getProfileProxy(HEADSET) failed");
+      return;
+    }
+    // Register receivers for BluetoothHeadset change notifications.
+    IntentFilter bluetoothHeadsetFilter = new IntentFilter();
+    // Register receiver for change in connection state of the Headset profile.
+    bluetoothHeadsetFilter.addAction(BluetoothHeadset.ACTION_CONNECTION_STATE_CHANGED);
+    // Register receiver for change in audio connection state of the Headset profile.
+    bluetoothHeadsetFilter.addAction(BluetoothHeadset.ACTION_AUDIO_STATE_CHANGED);
+    registerReceiver(bluetoothHeadsetReceiver, bluetoothHeadsetFilter);
+    Log.d(TAG, "HEADSET profile state: "
+            + stateToString(bluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEADSET)));
+    Log.d(TAG, "Bluetooth proxy for headset profile has started");
+    bluetoothState = State.HEADSET_UNAVAILABLE;
+    Log.d(TAG, "start done: BT state=" + bluetoothState);
+  }
+
+  /** Stops and closes all components related to Bluetooth audio. */
+  public void stop() {
+    threadChecker.checkIsOnValidThread();
+    unregisterReceiver(bluetoothHeadsetReceiver);
+    Log.d(TAG, "stop: BT state=" + bluetoothState);
+    if (bluetoothAdapter != null) {
+      // Stop BT SCO connection with remote device if needed.
+      stopScoAudio();
+      // Close down remaining BT resources.
+      if (bluetoothState != State.UNINITIALIZED) {
+        cancelTimer();
+        if (bluetoothHeadset != null) {
+          bluetoothAdapter.closeProfileProxy(BluetoothProfile.HEADSET, bluetoothHeadset);
+          bluetoothHeadset = null;
+        }
+        bluetoothAdapter = null;
+        bluetoothDevice = null;
+        bluetoothState = State.UNINITIALIZED;
+      }
+    }
+    Log.d(TAG, "stop done: BT state=" + bluetoothState);
+  }
+
+  /**
+   * Starts Bluetooth SCO connection with remote device.
+   * Note that the phone application always has the priority on the usage of the SCO connection
+   * for telephony. If this method is called while the phone is in call it will be ignored.
+   * Similarly, if a call is received or sent while an application is using the SCO connection,
+   * the connection will be lost for the application and NOT returned automatically when the call
+   * ends. Also note that: up to and including API version JELLY_BEAN_MR1, this method initiates a
+   * virtual voice call to the Bluetooth headset. After API version JELLY_BEAN_MR2 only a raw SCO
+   * audio connection is established.
+   * TODO(henrika): should we add support for virtual voice call to BT headset also for JBMR2 and
+   * higher. It might be required to initiates a virtual voice call since many devices do not
+   * accept SCO audio without a "call".
+   */
+  public boolean startScoAudio() {
+    threadChecker.checkIsOnValidThread();
+    Log.d(TAG, "startSco: BT state=" + bluetoothState + ", "
+            + "attempts: " + scoConnectionAttempts + ", "
+            + "SCO is on: " + isScoOn());
+    if (scoConnectionAttempts >= MAX_SCO_CONNECTION_ATTEMPTS) {
+      Log.e(TAG, "BT SCO connection fails - no more attempts");
+      return false;
+    }
+    if (bluetoothState != State.HEADSET_AVAILABLE) {
+      Log.e(TAG, "BT SCO connection fails - no headset available");
+      return false;
+    }
+    // Start BT SCO channel and wait for ACTION_AUDIO_STATE_CHANGED.
+    Log.d(TAG, "Starting Bluetooth SCO and waits for ACTION_AUDIO_STATE_CHANGED...");
+    // The SCO connection establishment can take several seconds, hence we cannot rely on the
+    // connection to be available when the method returns but instead register to receive the
+    // intent ACTION_SCO_AUDIO_STATE_UPDATED and wait for the state to be SCO_AUDIO_STATE_CONNECTED.
+    bluetoothState = State.SCO_CONNECTING;
+    audioManager.startBluetoothSco();
+    scoConnectionAttempts++;
+    startTimer();
+    Log.d(TAG, "startScoAudio done: BT state=" + bluetoothState);
+    return true;
+  }
+
+  /** Stops Bluetooth SCO connection with remote device. */
+  public void stopScoAudio() {
+    threadChecker.checkIsOnValidThread();
+    Log.d(TAG, "stopScoAudio: BT state=" + bluetoothState + ", "
+            + "SCO is on: " + isScoOn());
+    if (bluetoothState != State.SCO_CONNECTING && bluetoothState != State.SCO_CONNECTED) {
+      return;
+    }
+    cancelTimer();
+    audioManager.stopBluetoothSco();
+    bluetoothState = State.SCO_DISCONNECTING;
+    Log.d(TAG, "stopScoAudio done: BT state=" + bluetoothState);
+  }
+
+  /**
+   * Use the BluetoothHeadset proxy object (controls the Bluetooth Headset
+   * Service via IPC) to update the list of connected devices for the HEADSET
+   * profile. The internal state will change to HEADSET_UNAVAILABLE or to
+   * HEADSET_AVAILABLE and |bluetoothDevice| will be mapped to the connected
+   * device if available.
+   */
+  public void updateDevice() {
+    if (bluetoothState == State.UNINITIALIZED || bluetoothHeadset == null) {
+      return;
+    }
+    Log.d(TAG, "updateDevice");
+    // Get connected devices for the headset profile. Returns the set of
+    // devices which are in state STATE_CONNECTED. The BluetoothDevice class
+    // is just a thin wrapper for a Bluetooth hardware address.
+    List<BluetoothDevice> devices = bluetoothHeadset.getConnectedDevices();
+    if (devices.size() == 0) {

[magjed_webrtc, 2016/12/10 19:34:44]

nit: Use devices.isEmpty() instead.

[henrika_webrtc, 2016/12/12 14:13:25]

Done.

+      bluetoothDevice = null;
+    } else {
+      // Always use first device is list. Android only supports one device.
+      bluetoothDevice = devices.get(0);
+    }
+    if (bluetoothDevice == null) {

[magjed_webrtc, 2016/12/10 19:34:44]

Join this if-statement with the one above since they are the same. I.e.
if (devices.isEmpty()) {
  bluetoothDevice = null;
  bluetoothState = State.HEADSET_UNAVAILABLE;
  Log.d(TAG, "No connected bluetooth headset");
} else {
  // Always use first device is list. Android only supports one device.
  bluetoothDevice = devices.get(0);
  bluetoothState = State.HEADSET_AVAILABLE;
  Log.d(TAG, "Connected bluetooth headset: "
      + "name=" + bluetoothDevice.getName() + ", "
      + "state=" +
stateToString(bluetoothHeadset.getConnectionState(bluetoothDevice))
      + ", SCO audio=" + bluetoothHeadset.isAudioConnected(bluetoothDevice));
}

[henrika_webrtc, 2016/12/12 14:13:25]

Thanks. Done!

+      bluetoothState = State.HEADSET_UNAVAILABLE;
+      Log.d(TAG, "No connected bluetooth headset");
+    } else {
+      bluetoothState = State.HEADSET_AVAILABLE;
+      Log.d(TAG, "Connected bluetooth headset: "
+              + "name=" + bluetoothDevice.getName() + ", "
+              + "state=" + stateToString(bluetoothHeadset.getConnectionState(bluetoothDevice))
+              + ", SCO audio=" + bluetoothHeadset.isAudioConnected(bluetoothDevice));
+    }
+    Log.d(TAG, "updateDevice done: BT state=" + bluetoothState);
+  }
+
+  /**
+   * Stubs for test mocks.
+   */
+  protected AudioManager getAudioManager(Context context) {
+    return (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
+  }
+
+  protected void registerReceiver(BroadcastReceiver receiver, IntentFilter filter) {
+    apprtcContext.registerReceiver(receiver, filter);
+  }
+
+  protected void unregisterReceiver(BroadcastReceiver receiver) {
+    apprtcContext.unregisterReceiver(receiver);
+  }
+
+  protected boolean getBluetoothProfileProxy(
+      Context context, BluetoothProfile.ServiceListener listener, int profile) {
+    return bluetoothAdapter.getProfileProxy(context, listener, profile);
+  }
+
+  protected boolean hasPermission(Context context, String permission) {
+    return apprtcContext.checkPermission(permission, Process.myPid(), Process.myUid())
+        == PackageManager.PERMISSION_GRANTED;
+  }
+
+  /** Logs the state of the local Bluetooth adapter. */
+  protected void logBluetoothAdapterInfo(BluetoothAdapter localAdapter) {
+    Log.d(TAG, "BluetoothAdapter: "
+            + "enabled=" + localAdapter.isEnabled() + ", "
+            + "state=" + stateToString(localAdapter.getState()) + ", "
+            + "name=" + localAdapter.getName() + ", "
+            + "address=" + localAdapter.getAddress());
+    // Log the set of BluetoothDevice objects that are bonded (paired) to the local adapter.
+    Set<BluetoothDevice> pairedDevices = localAdapter.getBondedDevices();
+    if (pairedDevices.size() > 0) {

[magjed_webrtc, 2016/12/10 19:34:45]

nit: !pairedDevices.isEmpty()

[henrika_webrtc, 2016/12/12 14:13:25]

Done.

+      Log.d(TAG, "paired devices:");
+      for (BluetoothDevice device : pairedDevices) {
+        Log.d(TAG, " name=" + device.getName() + ", address=" + device.getAddress());
+      }
+    }
+  }
+
+  /** Ensures that the audio manager updates its list of available audio devices. */
+  private void updateAudioDeviceState() {
+    threadChecker.checkIsOnValidThread();
+    Log.d(TAG, "updateAudioDeviceState");
+    apprtcAudioManager.updateAudioDeviceState();
+  }
+
+  /** Starts timer which times out after BLUETOOTH_SCO_TIMEOUT_MS milliseconds. */
+  private void startTimer() {
+    threadChecker.checkIsOnValidThread();
+    Log.d(TAG, "startTimer");
+    handler.postDelayed(bluetoothTimeoutRunnable, BLUETOOTH_SCO_TIMEOUT_MS);
+  }
+
+  /** Cancels any outstanding timer tasks. */
+  private void cancelTimer() {
+    threadChecker.checkIsOnValidThread();
+    Log.d(TAG, "cancelTimer");
+    handler.removeCallbacks(bluetoothTimeoutRunnable);
+  }
+
+  /**
+   * Called when start of the BT SCO channel takes too long time. Usually
+   * happens when the BT device has been turned on during an ongoing call.
+   */
+  private void bluetoothTimeout() {
+    threadChecker.checkIsOnValidThread();
+    if (bluetoothState == State.UNINITIALIZED || bluetoothHeadset == null) {
+      return;
+    }
+    Log.d(TAG, "bluetoothTimeout: BT state=" + bluetoothState + ", "
+            + "attempts: " + scoConnectionAttempts + ", "
+            + "SCO is on: " + isScoOn());
+    if (bluetoothState != State.SCO_CONNECTING) {
+      return;
+    }
+    // Bluetooth SCO should be connecting; check the latest result.
+    boolean scoConnected = false;
+    List<BluetoothDevice> devices = bluetoothHeadset.getConnectedDevices();
+    if (devices.size() > 0) {
+      bluetoothDevice = devices.get(0);
+      if (bluetoothHeadset.isAudioConnected(bluetoothDevice)) {
+        Log.d(TAG, "SCO connected with " + bluetoothDevice.getName());
+        scoConnected = true;
+      } else {
+        Log.d(TAG, "SCO is not connected with " + bluetoothDevice.getName());
+      }
+    }
+    if (scoConnected) {
+      // We thought BT had timed out, but it's actually on; updating state.
+      bluetoothState = State.SCO_CONNECTED;
+      scoConnectionAttempts = 0;
+      updateAudioDeviceState();

[magjed_webrtc, 2016/12/10 19:34:44]

Move this after the if-statement since you do it last in both branches.

[henrika_webrtc, 2016/12/12 14:13:25]

Done.

+    } else {
+      // Give up and "cancel" our request by calling stopBluetoothSco().
+      Log.w(TAG, "BT failed to connect after timeout");
+      stopScoAudio();
+      updateAudioDeviceState();
+    }
+    Log.d(TAG, "bluetoothTimeout done: BT state=" + bluetoothState);
+  }
+
+  /** Checks whether audio uses Bluetooth SCO. */
+  private boolean isScoOn() {
+    return audioManager.isBluetoothScoOn();

[magjed_webrtc, 2016/12/10 19:34:44]

I personally would just inline audioManager.isBluetoothScoOn() instead of adding
a function for it, but I don't have a strong opinion about this.

[henrika_webrtc, 2016/12/12 14:13:25]

ACK, used same style in AudioManager. Keeping as is to be consistent.

+  }
+
+  /** Converts BluetoothAdapter states into local string representations. */
+  private String stateToString(int state) {
+    String stateString;
+    switch (state) {
+      case BluetoothAdapter.STATE_DISCONNECTED:
+        // The profile is in disconnected state.

[magjed_webrtc, 2016/12/10 19:34:45]

Remove |stateString| and just do
return "DISCONNECTED".
Similar for the other cases.

[henrika_webrtc, 2016/12/12 14:13:25]

Done.

+        stateString = "DISCONNECTED";
+        break;
+      case BluetoothAdapter.STATE_CONNECTED:
+        // The profile is in connected state.

[magjed_webrtc, 2016/12/10 19:34:45]

Many of these comments provide no extra information beyond the code, I would
just remove those. It looks like only BluetoothAdapter.STATE_TURNING_ON and
BluetoothAdapter.STATE_TURNING_OFF have interesting comments.

[henrika_webrtc, 2016/12/12 14:13:25]

Agree. Removed.

+        stateString = "CONNECTED";
+        break;
+      case BluetoothAdapter.STATE_CONNECTING:
+        // The profile is in connecting state.
+        stateString = "CONNECTING";
+        break;
+      case BluetoothAdapter.STATE_DISCONNECTING:
+        // The profile is in disconnecting state.
+        stateString = "DISCONNECTING";
+        break;
+      case BluetoothAdapter.STATE_OFF:
+        // Indicates the local Bluetooth adapter is off.
+        stateString = "OFF";
+        break;
+      case BluetoothAdapter.STATE_ON:
+        // Indicates the local Bluetooth adapter is on, and ready for use.
+        stateString = "ON";
+        break;
+      case BluetoothAdapter.STATE_TURNING_OFF:
+        // Indicates the local Bluetooth adapter is turning off. Local clients should immediately
+        // attempt graceful disconnection of any remote links.
+        stateString = "TURNING_OFF";
+        break;
+      case BluetoothAdapter.STATE_TURNING_ON:
+        // Indicates the local Bluetooth adapter is turning on. However local clients should wait
+        // for STATE_ON before attempting to use the adapter.
+        stateString = "TURNING_ON";
+        break;
+      default:
+        stateString = "INVALID";
+        break;
+    }
+    return stateString;
+  }
+}