Android Bluetooth Profile通信

随着智能设备的普及，蓝牙开发在手机应用端使用的越来越多。但是目前网上对蓝牙开发的介绍还相当少，刚开始接触蓝牙开发时，都是边网上搜边看源码，花费了不少功夫，总算是对蓝牙开发略知一二了。蓝牙设备之间建立连接分为三个部分：1.Bond（Pair）、2.Profile、3.Socket

1.Bond，Bond即设备之间绑定（配对），这是蓝牙设备之间通信的基础。当搜索到需要bond的设备时，获取到设备对应的BluetoothDevice对象时，我们就可以进行bond操作了。查看BluetoothDevice源码，在其方法中可以找到一个叫“createBond()”方法，该方法即是蓝牙bond的核心方法，但需要注意的是，该方法在API19之前是@hide的，所以minSdk设置小于API19时，需要通过反射来调用该方法

 /**     * Start the bonding (pairing) process with the remote device.     * <p>This is an asynchronous call, it will return immediately. Register     * for {@link #ACTION_BOND_STATE_CHANGED} intents to be notified when     * the bonding process completes, and its result.     * <p>Android system services will handle the necessary user interactions     * to confirm and complete the bonding process.     * <p>Requires {@link android.Manifest.permission#BLUETOOTH_ADMIN}.     *     * @return false on immediate error, true if bonding will begin     */    @RequiresPermission(Manifest.permission.BLUETOOTH_ADMIN)    public boolean createBond() {        if (sService == null) {            Log.e(TAG, "BT not enabled. Cannot create bond to Remote Device");            return false;        }        try {            return sService.createBond(this, TRANSPORT_AUTO);        } catch (RemoteException e) {Log.e(TAG, "", e);}        return false;    }

通过查看源码，不难看出，createBond方法在执行时，调用了IPC，需要了解具体实现过程的，可以去查看“sService ”这个IPC类的源码，这里就不再深入。

2.Profile，Profile是蓝牙的一个很重要特性，Profile定义了设备如何实现一种连接或者应用，你可以把Profile理解为连接层或者应用层协。
关于蓝牙Profile的介绍可以看这里：
下面来介绍Profile的连接：
在android framework层中，Profile同样是封装成了一个个IPC类，在BluetoothAdapter中提供了”getProfileProxy(Context context, BluetoothProfile.ServiceListener listener, int profile)”方法连接IPC实例获取到这些Profile服务的代理来操作这些profile以及”closeProfileProxy(int profile, BluetoothProfile profile)”来关闭这些Profile的代理

/**     * Get the profile proxy object associated with the profile.     *     * <p>Profile can be one of {@link BluetoothProfile#HEALTH}, {@link BluetoothProfile#HEADSET},     * {@link BluetoothProfile#A2DP}, {@link BluetoothProfile#GATT}, or     * {@link BluetoothProfile#GATT_SERVER}. Clients must implement     * {@link BluetoothProfile.ServiceListener} to get notified of     * the connection status and to get the proxy object.     *     * @param context Context of the application     * @param listener The service Listener for connection callbacks.     * @param profile The Bluetooth profile; either {@link BluetoothProfile#HEALTH},     *                {@link BluetoothProfile#HEADSET}, {@link BluetoothProfile#A2DP}.     *                {@link BluetoothProfile#GATT} or {@link BluetoothProfile#GATT_SERVER}.     * @return true on success, false on error     */    public boolean getProfileProxy(Context context, BluetoothProfile.ServiceListener listener,                                   int profile) {        if (context == null || listener == null) return false;        if (profile == BluetoothProfile.HEADSET) {            BluetoothHeadset headset = new BluetoothHeadset(context, listener);            return true;        } else if (profile == BluetoothProfile.A2DP) {            BluetoothA2dp a2dp = new BluetoothA2dp(context, listener);            return true;        } else if (profile == BluetoothProfile.A2DP_SINK) {            BluetoothA2dpSink a2dpSink = new BluetoothA2dpSink(context, listener);            return true;        } else if (profile == BluetoothProfile.AVRCP_CONTROLLER) {            BluetoothAvrcpController avrcp = new BluetoothAvrcpController(context, listener);            return true;        } else if (profile == BluetoothProfile.INPUT_DEVICE) {            BluetoothInputDevice iDev = new BluetoothInputDevice(context, listener);            return true;        } else if (profile == BluetoothProfile.PAN) {            BluetoothPan pan = new BluetoothPan(context, listener);            return true;        } else if (profile == BluetoothProfile.HEALTH) {            BluetoothHealth health = new BluetoothHealth(context, listener);            return true;        } else if (profile == BluetoothProfile.MAP) {            BluetoothMap map = new BluetoothMap(context, listener);            return true;        } else if (profile == BluetoothProfile.HEADSET_CLIENT) {            BluetoothHeadsetClient headsetClient = new BluetoothHeadsetClient(context, listener);            return true;        } else if (profile == BluetoothProfile.SAP) {            BluetoothSap sap = new BluetoothSap(context, listener);            return true;        } else {            return false;        }    }

该方法支持连接HEADSET、A2DP、A2DP_SINK、AVRCP、INPUT_DEVICE、PAN、HEALTH、MAP、HEADSET_CLIENT、SAP等相应的Profile。参数中，BluetoothProfile.SearchListener是对外用来监听是否成功连接Profile的IPC实例的，与普通AIDL用来监听连接的ServiceConnection类似，当“onServiceConnected(int profile, BluetoothProfile proxy)”被调用时，我们就可以获取到该Profile的IPC实例来做我们想做的事情。这里已Headset来讲解Profile连接设备的方式，其实上述这些Profile的连接方式都大同小异。在上面方法中，当获取HEADSET Profile时，生成了一个BluetoothHeadset对象，该对象即是Headset IPC的代理，在该类中有"connect(BluetoothDevice device)"、"disconnect(BluetoothDevice device)"方法来连接和断开与设备的Profile链接等。

/**     * Initiate connection to a profile of the remote bluetooth device.     *     * <p> Currently, the system supports only 1 connection to the     * headset/handsfree profile. The API will automatically disconnect connected     * devices before connecting.     *     * <p> This API returns false in scenarios like the profile on the     * device is already connected or Bluetooth is not turned on.     * When this API returns true, it is guaranteed that     * connection state intent for the profile will be broadcasted with     * the state. Users can get the connection state of the profile     * from this intent.     *     * <p>Requires {@link android.Manifest.permission#BLUETOOTH_ADMIN}     * permission.     *     * @param device Remote Bluetooth Device     * @return false on immediate error,     *               true otherwise     * @hide     */    public boolean connect(BluetoothDevice device) {        if (DBG) log("connect(" + device + ")");        if (mService != null && isEnabled() &&            isValidDevice(device)) {            try {                return mService.connect(device);            } catch (RemoteException e) {                Log.e(TAG, Log.getStackTraceString(new Throwable()));                return false;            }        }        if (mService == null) Log.w(TAG, "Proxy not attached to service");        return false;    }    /**     * Initiate disconnection from a profile     *     * <p> This API will return false in scenarios like the profile on the     * Bluetooth device is not in connected state etc. When this API returns,     * true, it is guaranteed that the connection state change     * intent will be broadcasted with the state. Users can get the     * disconnection state of the profile from this intent.     *     * <p> If the disconnection is initiated by a remote device, the state     * will transition from {@link #STATE_CONNECTED} to     * {@link #STATE_DISCONNECTED}. If the disconnect is initiated by the     * host (local) device the state will transition from     * {@link #STATE_CONNECTED} to state {@link #STATE_DISCONNECTING} to     * state {@link #STATE_DISCONNECTED}. The transition to     * {@link #STATE_DISCONNECTING} can be used to distinguish between the     * two scenarios.     *     * <p>Requires {@link android.Manifest.permission#BLUETOOTH_ADMIN}     * permission.     *     * @param device Remote Bluetooth Device     * @return false on immediate error,     *               true otherwise     * @hide     */    public boolean disconnect(BluetoothDevice device) {        if (DBG) log("disconnect(" + device + ")");        if (mService != null && isEnabled() &&            isValidDevice(device)) {            try {                return mService.disconnect(device);            } catch (RemoteException e) {              Log.e(TAG, Log.getStackTraceString(new Throwable()));              return false;            }        }        if (mService == null) Log.w(TAG, "Proxy not attached to service");        return false;    }

源码中都有非常详细的方法介绍，这里就不再敖诉。关于连接蓝牙Profile的例子，可以参考这里：

3.Socket，绑定后的蓝牙设备之间是可以建立Socket通信的，这种Socket类似于TCP Socket，但略有不同，该Socket只能通过调用Android API来获取并连接，但通信操作是与TCP相同的，可以获取InputStream以及OutputStream来实现数据的交互。在蓝牙规范中，有个SPP(全称Serial Port Profile) Profile，定义了如何在两台蓝牙设备之间建立虚拟串口并进行连接，顾名思义，就是来支持蓝牙设备之间的Socket通信。该Profile在蓝牙设备绑定之后便会连接，所以我们只需在蓝牙绑定成功后，通过调用相应的API，即可获取BluetoothSocket对象，在该对象中提供了”getInputStream”、”getOutputStream”来获取输入输出流，然后即可通过IO流来传输数据，实现设备通讯。

一般的，我们通过连接该Socket来实现手机控制智能设备的功能，但是Socket也仅仅只能用来数据通讯，要想实现免提电话、听音乐、外接键盘等功能，还是需要去连接对应的Profile。

下面附上自己做的一个小Demo：https://github.com/Joy-Whale/BluetoothProfile