[Android实例] android 蓝牙开发浅析

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

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());     

    }     

}     

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）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
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) { }    
 }     } 

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) { }    
   
    }    
   
}