Android 蓝牙浅析

 

由于近期正在开发一个通过蓝牙进行数据传递的模块，在参考了有关资料，并详细阅读了Android的官方文档后，总结了Android中蓝牙模块的使用。

1. 使用蓝牙的响应权限
[html]
<uses-permission android:name="android.permission.BLUETOOTH" /> 
<uses-permission android:name="android.permission.BLUETOOTH_ADMIN" /> 

2. 配置本机蓝牙模块
在这里首先要了解对蓝牙操作一个核心类BluetoothAdapter
[java]
BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter(); 
//直接打开系统的蓝牙设置面板 
Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); 
startActivityForResult(intent, 0x1); 
//直接打开蓝牙 
adapter.enable(); 
//关闭蓝牙 
adapter.disable(); 
//打开本机的蓝牙发现功能（默认打开120秒，可以将时间最多延长至300秒） 
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);//设置持续时间（最多300秒）Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); 

3.搜索蓝牙设备
使用BluetoothAdapter的startDiscovery()方法来搜索蓝牙设备
startDiscovery()方法是一个异步方法，调用后会立即返回。该方法会进行对其他蓝牙设备的搜索，该过程会持续12秒。该方法调用后，搜索过程实际上是在一个System Service中进行的，所以可以调用cancelDiscovery()方法来停止搜索（该方法可以在未执行discovery请求时调用）。
请求Discovery后，系统开始搜索蓝牙设备，在这个过程中，系统会发送以下三个广播：
ACTION_DISCOVERY_START：开始搜索
ACTION_DISCOVERY_FINISHED：搜索结束
ACTION_FOUND：找到设备，这个Intent中包含两个extra fields：EXTRA_DEVICE和EXTRA_CLASS，分别包含BluetooDevice和BluetoothClass。
我们可以自己注册相应的BroadcastReceiver来接收响应的广播，以便实现某些功能
[java]
// 创建一个接收ACTION_FOUND广播的BroadcastReceiver 
private final BroadcastReceiver mReceiver = new BroadcastReceiver() { 
    public void onReceive(Context context, Intent intent) { 
        String action = intent.getAction(); 
        // 发现设备 
        if (BluetoothDevice.ACTION_FOUND.equals(action)) { 
            // 从Intent中获取设备对象 
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); 
            // 将设备名称和地址放入array adapter，以便在ListView中显示 
            mArrayAdapter.add(device.getName() + "\n" + device.getAddress()); 
        } 
    } 
}; 
// 注册BroadcastReceiver 
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND); 
registerReceiver(mReceiver, filter); // 不要忘了之后解除绑定 

4. 蓝牙Socket通信
如果打算建议两个蓝牙设备之间的连接，则必须实现服务器端与客户端的机制。当两个设备在同一个RFCOMM channel下分别拥有一个连接的BluetoothSocket，这两个设备才可以说是建立了连接。
服务器设备与客户端设备获取BluetoothSocket的途径是不同的。服务器设备是通过accepted一个incoming connection来获取的，而客户端设备则是通过打开一个到服务器的RFCOMM channel来获取的。

服务器端的实现
通过调用BluetoothAdapter的listenUsingRfcommWithServiceRecord(String, UUID)方法来获取BluetoothServerSocket（UUID用于客户端与服务器端之间的配对）
调用BluetoothServerSocket的accept()方法监听连接请求，如果收到请求，则返回一个BluetoothSocket实例（此方法为block方法，应置于新线程中）
如果不想在accept其他的连接，则调用BluetoothServerSocket的close()方法释放资源（调用该方法后，之前获得的BluetoothSocket实例并没有close。但由于RFCOMM一个时刻只允许在一条channel中有一个连接，则一般在accept一个连接后，便close掉BluetoothServerSocket）
[java]
private class AcceptThread extends Thread { 
    private final BluetoothServerSocket mmServerSocket; 
 
    public AcceptThread() { 
        // Use a temporary object that is later assigned to mmServerSocket, 
        // because mmServerSocket is final 
        BluetoothServerSocket tmp = null; 
        try { 
            // MY_UUID is the app's UUID string, also used by the client code 
            tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME, MY_UUID); 
        } catch (IOException e) { } 
        mmServerSocket = tmp; 
    } 
 
    public void run() { 
        BluetoothSocket socket = null; 
        // Keep listening until exception occurs or a socket is returned 
        while (true) { 
            try { 
                socket = mmServerSocket.accept(); 
            } catch (IOException e) { 
                break; 
            } 
            // If a connection was accepted 
            if (socket != null) { 
                // Do work to manage the connection (in a separate thread) 
                manageConnectedSocket(socket); 
                mmServerSocket.close(); 
                break; 
            } 
        } 
    } 
 
    /** Will cancel the listening socket, and cause the thread to finish */ 
    public void cancel() { 
        try { 
            mmServerSocket.close(); 
        } catch (IOException e) { } 
    } 
} 

客户端的实现 www.2cto.com
通过搜索得到服务器端的BluetoothService
调用BluetoothService的listenUsingRfcommWithServiceRecord(String, UUID)方法获取BluetoothSocket（该UUID应该同于服务器端的UUID）
调用BluetoothSocket的connect()方法（该方法为block方法），如果UUID同服务器端的UUID匹配，并且连接被服务器端accept，则connect()方法返回
注意：在调用connect()方法之前，应当确定当前没有搜索设备，否则连接会变得非常慢并且容易失败
[java]
private class ConnectThread extends Thread { 
    private final BluetoothSocket mmSocket; 
    private final BluetoothDevice mmDevice; 
 
    public ConnectThread(BluetoothDevice device) { 
        // Use a temporary object that is later assigned to mmSocket, 
        // because mmSocket is final 
        BluetoothSocket tmp = null; 
        mmDevice = device; 
 
        // Get a BluetoothSocket to connect with the given BluetoothDevice 
        try { 
            // MY_UUID is the app's UUID string, also used by the server code 
            tmp = device.createRfcommSocketToServiceRecord(MY_UUID); 
        } catch (IOException e) { } 
        mmSocket = tmp; 
    } 
 
    public void run() { 
        // Cancel discovery because it will slow down the connection 
        mBluetoothAdapter.cancelDiscovery(); 
 
        try { 
            // Connect the device through the socket. This will block 
            // until it succeeds or throws an exception 
            mmSocket.connect(); 
        } catch (IOException connectException) { 
            // Unable to connect; close the socket and get out 
            try { 
                mmSocket.close(); 
            } catch (IOException closeException) { } 
            return; 
        } 
 
        // Do work to manage the connection (in a separate thread) 
        manageConnectedSocket(mmSocket); 
    } 
 
    /** Will cancel an in-progress connection, and close the socket */ 
    public void cancel() { 
        try { 
            mmSocket.close(); 
        } catch (IOException e) { } 
    } 
} 

连接管理（数据通信）
分别通过BluetoothSocket的getInputStream()和getOutputStream()方法获取InputStream和OutputStream
使用read(bytes[])和write(bytes[])方法分别进行读写操作
注意：read(bytes[])方法会一直block，知道从流中读取到信息，而write(bytes[])方法并不是经常的block（比如在另一设备没有及时read或者中间缓冲区已满的情况下，write方法会block）
[java]
private class ConnectedThread extends Thread { 
    private final BluetoothSocket mmSocket; 
    private final InputStream mmInStream; 
    private final OutputStream mmOutStream; 
 
    public ConnectedThread(BluetoothSocket socket) { 
        mmSocket = socket; 
        InputStream tmpIn = null; 
        OutputStream tmpOut = null; 
 
        // Get the input and output streams, using temp objects because 
        // member streams are final 
        try { 
            tmpIn = socket.getInputStream(); 
            tmpOut = socket.getOutputStream(); 
        } catch (IOException e) { } 
 
        mmInStream = tmpIn; 
        mmOutStream = tmpOut; 
    } 
 
    public void run() { 
        byte[] buffer = new byte[1024];  // buffer store for the stream 
        int bytes; // bytes returned from read() 
 
        // Keep listening to the InputStream until an exception occurs 
        while (true) { 
            try { 
                // Read from the InputStream 
                bytes = mmInStream.read(buffer); 
                // Send the obtained bytes to the UI Activity 
                mHandler.obtainMessage(MESSAGE_READ, bytes, -1, buffer) 
                        .sendToTarget(); 
            } catch (IOException e) { 
                break; 
            } 
        } 
    } 
 
    /* Call this from the main Activity to send data to the remote device */ 
    public void write(byte[] bytes) { 
        try { 
            mmOutStream.write(bytes); 
        } catch (IOException e) { } 
    } 
 
    /* Call this from the main Activity to shutdown the connection */ 
    public void cancel() { 
        try { 
            mmSocket.close(); 
        } catch (IOException e) { } 
    } 
}