Android 蓝牙基础篇之 —— A2DP

本篇文章主要介绍 A2DP 基础操作。

• 介绍

A2DP ：Advanced Audio Distribution Profile。高质量音频数据传输的协议，其定义里了传送单声道或立体声等高质量音频（区别于蓝牙SCO链路上传输的普通语音）信息的协议和过程。A2DP的典型应用是将音乐播放器的音频数据发送到耳机或音箱。

A2DP 定义了两种角色：

Audio Source ：（音频源） 音频的输入端对音频数据进行编码，发送到Sink端。
Audio Sink ：     （音频接收器） 接收到音频数据后，进行解码操作还原出音频。

 

• 初始化 A2DP 代理对象

  private void initBluetooth() {mBtAdapter = BluetoothAdapter.getDefaultAdapter();if (!mBtAdapter.isEnabled()) {return;}//获取A2DP代理对象mBtAdapter.getProfileProxy(mContext, mListener, BluetoothProfile.A2DP);}private void initReceiver() {//广播接收者监听状态IntentFilter filter = new IntentFilter(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED);filter.addAction(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED);mContext.registerReceiver(mReceiver, filter);}

• 初始化 A2DP 代理对象

  private void initBluetooth() {mBtAdapter = BluetoothAdapter.getDefaultAdapter();if (!mBtAdapter.isEnabled()) {return;}//获取A2DP代理对象mBtAdapter.getProfileProxy(mContext, mListener, BluetoothProfile.A2DP);}private void initReceiver() {//广播接收者监听状态IntentFilter filter = new IntentFilter(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED);filter.addAction(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED);mContext.registerReceiver(mReceiver, filter);}

• 广播接收者，获取连接状态

private BroadcastReceiver mReceiver = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {String action = intent.getAction();//A2DP连接状态改变if (action != null) {if (action.equals(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED)) {int state = intent.getIntExtra(BluetoothA2dp.EXTRA_STATE, BluetoothA2dp.STATE_DISCONNECTED);callBackA2dpConnectState(state);} else if (action.equals(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED)) {//A2DP播放状态改变int state = intent.getIntExtra(BluetoothA2dp.EXTRA_STATE, BluetoothA2dp.STATE_NOT_PLAYING);Log.i(TAG, "play state=" + state);}}}};

• 获取 A2DP 代理对象 proxy 

  private BluetoothProfile.ServiceListener mListener = new BluetoothProfile.ServiceListener() {@Overridepublic void onServiceDisconnected(int profile) {Log.i(TAG, "onServiceDisconnected profile=" + profile);if (profile == BluetoothProfile.A2DP) {mA2dp = null;}}@Overridepublic void onServiceConnected(int profile, BluetoothProfile proxy) {Log.i(TAG, "onServiceConnected profile=" + profile);if (profile == BluetoothProfile.A2DP) {mA2dp = (BluetoothA2dp) proxy; //转换if (onBluetoothA2dpReadyListener != null) {onBluetoothA2dpReadyListener.onBluetoothA2dpReady();}}}};

• 连接

 a2dp connect is hide  需要通过反射获取，连接成功之后，可以在蓝牙设备中播放音乐等音频

   public void connectA2dp(BluetoothDevice device) {Log.i(TAG, "connect to device :" + device);mConnectDevice = device;setPriority(device, 100); //设置prioritytry {//通过反射获取BluetoothA2dp中connect方法（hide的），进行连接。Method connectMethod = BluetoothA2dp.class.getMethod("connect",BluetoothDevice.class);connectMethod.invoke(mA2dp, device);} catch (Exception e) {e.printStackTrace();}}

• 断开连接

 public void disConnectA2dp(BluetoothDevice device) {mConnectDevice = null;setPriority(device, 0);try {//通过反射获取BluetoothA2dp中connect方法（hide的），断开连接。Method connectMethod = BluetoothA2dp.class.getMethod("disconnect",BluetoothDevice.class);connectMethod.invoke(mA2dp, device);} catch (Exception e) {e.printStackTrace();}}

• 设置优先级，一般 priority = 100

    public void setPriority(BluetoothDevice device, int priority) {if (mA2dp == null) return;try {//通过反射获取BluetoothA2dp中setPriority方法（hide的），设置优先级Method connectMethod = BluetoothA2dp.class.getMethod("setPriority",BluetoothDevice.class, int.class);connectMethod.invoke(mA2dp, device, priority);} catch (Exception e) {e.printStackTrace();}}

好了，到这里相信大家都明白了，HFP 和 A2DP 的操作流程基本一样。