本篇文章主要介紹 A2DP 基礎操作。

• 介紹

A2DP ：Advanced Audio Distribution Profile。高質量音頻數據傳輸的協議，其定義里了傳送單聲道或立體聲等高質量音頻（區別于藍牙SCO鏈路上傳輸的普通語音）信息的協議和過程。A2DP的典型應用是將音樂播放器的音頻數據發送到耳機或音箱。

A2DP 定義了兩種角色：

Audio Source ：（音頻源） 音頻的輸入端對音頻數據進行編碼，發送到Sink端。
Audio Sink ： ? ? （音頻接收器） 接收到音頻數據后，進行解碼操作還原出音頻。

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• 初始化 A2DP 代理對象

  private void initBluetooth() {mBtAdapter = BluetoothAdapter.getDefaultAdapter();if (!mBtAdapter.isEnabled()) {return;}//獲取A2DP代理對象mBtAdapter.getProfileProxy(mContext, mListener, BluetoothProfile.A2DP);}private void initReceiver() {//廣播接收者監聽狀態IntentFilter filter = new IntentFilter(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED);filter.addAction(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED);mContext.registerReceiver(mReceiver, filter);}

• 初始化 A2DP 代理對象

  private void initBluetooth() {mBtAdapter = BluetoothAdapter.getDefaultAdapter();if (!mBtAdapter.isEnabled()) {return;}//獲取A2DP代理對象mBtAdapter.getProfileProxy(mContext, mListener, BluetoothProfile.A2DP);}private void initReceiver() {//廣播接收者監聽狀態IntentFilter filter = new IntentFilter(BluetoothA2dp.ACTION_CONNECTION_STATE_CHANGED);filter.addAction(BluetoothA2dp.ACTION_PLAYING_STATE_CHANGED);mContext.registerReceiver(mReceiver, filter);}

• 廣播接收者，獲取連接狀態

private BroadcastReceiver mReceiver = new BroadcastReceiver() {@Overridepublic void onReceive(Context context, Intent intent) {String action = intent.getAction();//A2DP連接狀態改變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播放狀態改變int state = intent.getIntExtra(BluetoothA2dp.EXTRA_STATE, BluetoothA2dp.STATE_NOT_PLAYING);Log.i(TAG, "play state=" + state);}}}};

• 獲取 A2DP 代理對象 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; //轉換if (onBluetoothA2dpReadyListener != null) {onBluetoothA2dpReadyListener.onBluetoothA2dpReady();}}}};

• 連接

?a2dp connect is hide? 需要通過反射獲取，連接成功之后，可以在藍牙設備中播放音樂等音頻

   public void connectA2dp(BluetoothDevice device) {Log.i(TAG, "connect to device :" + device);mConnectDevice = device;setPriority(device, 100); //設置prioritytry {//通過反射獲取BluetoothA2dp中connect方法（hide的），進行連接。Method connectMethod = BluetoothA2dp.class.getMethod("connect",BluetoothDevice.class);connectMethod.invoke(mA2dp, device);} catch (Exception e) {e.printStackTrace();}}

• 斷開連接

 public void disConnectA2dp(BluetoothDevice device) {mConnectDevice = null;setPriority(device, 0);try {//通過反射獲取BluetoothA2dp中connect方法（hide的），斷開連接。Method connectMethod = BluetoothA2dp.class.getMethod("disconnect",BluetoothDevice.class);connectMethod.invoke(mA2dp, device);} catch (Exception e) {e.printStackTrace();}}

• 設置優先級，一般 priority = 100

    public void setPriority(BluetoothDevice device, int priority) {if (mA2dp == null) return;try {//通過反射獲取BluetoothA2dp中setPriority方法（hide的），設置優先級Method connectMethod = BluetoothA2dp.class.getMethod("setPriority",BluetoothDevice.class, int.class);connectMethod.invoke(mA2dp, device, priority);} catch (Exception e) {e.printStackTrace();}}

好了，到這里相信大家都明白了，HFP 和 A2DP 的操作流程基本一樣。

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