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.
* 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.
*
Android system services will handle the necessary user interactions
* to confirm and complete the bonding process.
*
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.
*
* 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.
*
* Currently, the system supports only 1 connection to the
* headset/handsfree profile. The API will automatically disconnect connected
* devices before connecting.
*
*
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.
*
*
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
*
*
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.
*
*
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.
*
*
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。