Android 如何获取已连接的蓝牙设备

项目中有一个需求，就是获取已连接的蓝牙地址

 private void getConnectBt() {
         LogUtil.i("getConnectBt");

         int a2dp = _bluetoothAdapter.getProfileConnectionState(BluetoothProfile.A2DP);
         int headset = _bluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEADSET);
         int health = _bluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEALTH);
         int flag = -1;
         if (a2dp == BluetoothProfile.STATE_CONNECTED) {
             flag = a2dp;
         } else if (headset == BluetoothProfile.STATE_CONNECTED) {
             flag = headset;
         } else if (health == BluetoothProfile.STATE_CONNECTED) {
             flag = health;
         }

         Log.d(TAG,"flag:"+flag);
         if (flag != -1) {
         _bluetoothAdapter.getProfileProxy(_context, new BluetoothProfile.ServiceListener() {
             @Override
             public void onServiceDisconnected(int profile) {

             }

             @Override
             public void onServiceConnected(int profile, BluetoothProfile proxy) {
                 List mDevices = proxy.getConnectedDevices();
                 if (mDevices != null && mDevices.size() > 0) {
                     for (BluetoothDevice device : mDevices) {
                         Log.d(TAG,device.getName() + "," + device.getAddress());
                     }
                 } else {

                 }
             }
         }, flag);

         }
     }

从网上看到这段代码并没有作用，由于flag一直等于-1，所以一直返回BluetoothProfile.STATE_DISCONNECTED。也就是说

 int a2dp = _bluetoothAdapter.getProfileConnectionState(BluetoothProfile.A2DP);
 int headset = _bluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEADSET);
 int health = _bluetoothAdapter.getProfileConnectionState(BluetoothProfile.HEALTH);

这三个方法都是返回的BluetoothProfile.STATE_DISCONNECTED

 /**
  * Get the current connection state of a profile.
  * This function can be used to check whether the local Bluetooth adapter
  * is connected to any remote device for a specific profile.
  * Profile can be one of {@link BluetoothProfile#HEALTH}, {@link BluetoothProfile#HEADSET},
  * {@link BluetoothProfile#A2DP}.
  *
  * Requires {@link android.Manifest.permission#BLUETOOTH}.
  *
  *  Return value can be one of
  * {@link BluetoothProfile#STATE_DISCONNECTED},
  * {@link BluetoothProfile#STATE_CONNECTING},
  * {@link BluetoothProfile#STATE_CONNECTED},
  * {@link BluetoothProfile#STATE_DISCONNECTING}
  */
 public int getProfileConnectionState(int profile) {
     if (getState() != STATE_ON) return BluetoothProfile.STATE_DISCONNECTED;
     try {
         synchronized(mManagerCallback) {
             if (mService != null) return mService.getProfileConnectionState(profile);
         }
     } catch (RemoteException e) {
         Log.e(TAG, "getProfileConnectionState:", e);
     }
     return BluetoothProfile.STATE_DISCONNECTED;
 }

mService是IBluetooth接口对象

 /**
  * Use {@link #getDefaultAdapter} to get the BluetoothAdapter instance.
  */
 BluetoothAdapter(IBluetoothManager managerService) {

     if (managerService == null) {
         throw new IllegalArgumentException("bluetooth manager service is null");
     }
     try {
         mService = managerService.registerAdapter(mManagerCallback);
     } catch (RemoteException e) {Log.e(TAG, "", e);}
     mManagerService = managerService;
     mLeScanClients = new HashMap();
     mHandler = new Handler(Looper.getMainLooper());
 }

 public static synchronized BluetoothAdapter getDefaultAdapter() {
     if (sAdapter == null) {
         IBinder b = ServiceManager.getService(BLUETOOTH_MANAGER_SERVICE);
         if (b != null) {
             IBluetoothManager managerService = IBluetoothManager.Stub.asInterface(b);
             sAdapter = new BluetoothAdapter(managerService);
         } else {
             Log.e(TAG, "Bluetooth binder is null");
         }
     }
     return sAdapter;
 }

我们看到managerService是IBluetoothManager的Proxy，我们来找找Stub端在哪。

 private static class AdapterServiceBinder extends IBluetooth.Stub

 class BluetoothManagerService extends IBluetoothManager.Stub

 public IBluetooth registerAdapter(IBluetoothManagerCallback callback){
     Message msg = mHandler.obtainMessage(MESSAGE_REGISTER_ADAPTER);
     msg.obj = callback;
     mHandler.sendMessage(msg);
     synchronized(mConnection) {
         return mBluetooth;
     }
 }

我们继续看BluetoothAdapter的mService到底是什么

 mBluetooth = IBluetooth.Stub.asInterface(service);

 private static class AdapterServiceBinder extends IBluetooth.Stub

原来BluetoothAdapter的mService = mBluetooth = IBluetooth.Stub.asInterface(service)，BluetoothManagerService只是个门面而已，真正干活的是IBluetooth.Stub也就是AdapterServiceBinder。我们回到最开始的问题，我们看AdapterService的getProfileConnectionState方法

 int getProfileConnectionState(int profile) {
    enforceCallingOrSelfPermission(BLUETOOTH_PERM, "Need BLUETOOTH permission");

    return mAdapterProperties.getProfileConnectionState(profile);

我们继续看AdapterProperties类

 int getProfileConnectionState(int profile) {
     synchronized (mObject) {
         Pair p = mProfileConnectionState.get(profile);
         if (p != null) return p.first;
         return BluetoothProfile.STATE_DISCONNECTED;
     }
 }

mProfileConnectionState是干什么用的，在此之前我们先看看蓝牙的一些基本概念。

BluetoothProfile
描述Bluetooth Profile的接口。Bluetooth Profile是两个设备基于蓝牙通讯的无线接口描述。
（对Bluetooth Profile的详细解释，来自百度：为了更容易的保持Bluetooth设备之间的兼容，Bluetooth规范中定义了 Profile。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议。 比如，如果一家公司希望它们的Bluetooth芯片支援所有的Bluetooth耳机，那么它只要支持HeadSet Profile即可，而无须考虑该芯片与其它Bluetooth设备的通讯与兼容性问题。如果你想购买Bluetooth产品，你应该了解你的应用需要哪 些Profile来完成，并且确保你购买的Bluetooth产品支持这些Profile。）
BluetoothHeadset
提供移动电话的Bluetooth耳机支持。包括Bluetooth耳机和Hands-Free (v1.5) profiles。
BluetoothA2dp
定义两个设备间如何通过Bluetooth连接进行高质量的音频传输。
A2DP（Advanced Audio Distribution Profile）：高级音频传输模式。

mProfileConnectionState也就是管理各种profile连接情况的一个集合

很显然，我们最开始那段代码不起作用，是因为profile不对,我们来看profile都有哪些

 /**
      * Headset and Handsfree profile
      */
     public static final int HEADSET = 1;

     /**
      * A2DP profile.
      */
     public static final int A2DP = 2;

     /**
      * Health Profile
      */
     public static final int HEALTH = 3;

     /**
      * Input Device Profile
      * @hide
      */
     public static final int INPUT_DEVICE = 4;

     /**
      * PAN Profile
      * @hide
      */
     public static final int PAN = 5;

     /**
      * PBAP
      * @hide
      */
     public static final int PBAP = 6;

     /**
      * GATT
      */
     static public final int GATT = 7;

     /**
      * GATT_SERVER
      */
     static public final int GATT_SERVER = 8;

我们列举了主要的几种，除了我们测试的HEADSET、A2DP、HEALTH外，还有GATT和GATT_SERVER，其实都是Hide。最开始的代码加上GATT和GATT_SERVER之后，依然没有结果。

实在没有办法了，我看到了BluetoothAdapter有一个hide方法直接调用了AdapterProperties的getConnectionState方法。

 /**
  * @return the mConnectionState
  */
 int getConnectionState() {
     synchronized (mObject) {
         return mConnectionState;
     }
 }

 Class bluetoothAdapterClass = BluetoothAdapter.class;//得到BluetoothAdapter的Class对象
        try {//得到蓝牙状态的方法
            Method method = bluetoothAdapterClass.getDeclaredMethod("getConnectionState", (Class[]) null);
            //打开权限
            method.setAccessible(true);
            int state = (int) method.invoke(_bluetoothAdapter, (Object[]) null);

            if(state == BluetoothAdapter.STATE_CONNECTED){

                LogUtil.i("BluetoothAdapter.STATE_CONNECTED");

                Set devices = _bluetoothAdapter.getBondedDevices();
                LogUtil.i("devices:"+devices.size());

                for(BluetoothDevice device : devices){

                    Method isConnectedMethod = BluetoothDevice.class.getDeclaredMethod("isConnected", (Class[]) null);
                    method.setAccessible(true);
                    boolean isConnected = (boolean) isConnectedMethod.invoke(device, (Object[]) null);

                    if(isConnected){
                        LogUtil.i("connected:"+device.getAddress());
                        return device.getAddress();
                    }

                }

            }

        } catch (Exception e) {
            e.printStackTrace();
        }

利用反射获取了当前蓝牙连接的状态，根据getBondedDevices获取已绑定的蓝牙连接，然后遍历BluetoothDevice，同样利用反射的方法调用BluetoothDevice的isConnected方法。成功获取。

参考文章：

http://blog.csdn.net/mapeifan/article/details/50683956