2. 配置本機藍芽模組

在這裡首先要了解對藍芽操作一個核心類BluetoothAdapter

程式碼如下:
BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();
//直接開啟系統的藍芽設定面板
Intent intent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
startActivityForResult(intent, 0x1);
//直接開啟藍芽
adapter.enable();
//關閉藍芽
adapter.disable();
//開啟本機的藍芽發現功能（預設開啟120秒，可以將時間最多延長至300秒）
Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE);
discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);//設定持續時間（最多300秒）

3.搜尋藍芽裝置

使用BluetoothAdapter的startDiscovery()方法來搜尋藍芽裝置

startDiscovery()方法是一個非同步方法，呼叫後會立即返回。該方法會進行對其他藍芽裝置的搜尋，該過程會持續12秒。該方法呼叫後，搜尋過程實際上是在一個System Service中進行的，所以可以呼叫cancelDiscovery()方法來停止搜尋（該方法可以在未執行discovery請求時呼叫）。

請求Discovery後，系統開始搜尋藍芽裝置，在這個過程中，系統會發送以下三個廣播：

ACTION_DISCOVERY_START：開始搜尋

ACTION_DISCOVERY_FINISHED：搜尋結束

ACTION_FOUND：找到裝置，這個Intent中包含兩個extra fields：EXTRA_DEVICE和EXTRA_CLASS，分別包含BluetooDevice和BluetoothClass。

我們可以自己註冊相應的BroadcastReceiver來接收響應的廣播，以便實現某些功能

程式碼如下:
// 建立一個接收ACTION_FOUND廣播的BroadcastReceiver
private final BroadcastReceiver mReceiver = new BroadcastReceiver() {
    public void onReceive(Context context, Intent intent) {
        String action = intent.getAction();
        // 發現裝置
        if (BluetoothDevice.ACTION_FOUND.equals(action)) {
            // 從Intent中獲取裝置物件
            BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
            // 將裝置名稱和地址放入array adapter，以便在ListView中顯示
            mArrayAdapter.add(device.getName() + "\n" + device.getAddress());
        }
    }
};
// 註冊BroadcastReceiver
IntentFilter filter = new IntentFilter(BluetoothDevice.ACTION_FOUND);
registerReceiver(mReceiver, filter); // 不要忘了之後解除繫結

4. 藍芽Socket通訊

如果打算建議兩個藍芽裝置之間的連線，則必須實現伺服器端與客戶端的機制。當兩個裝置在同一個RFCOMM channel下分別擁有一個連線的BluetoothSocket，這兩個裝置才可以說是建立了連線。

伺服器裝置與客戶端裝置獲取BluetoothSocket的途徑是不同的。伺服器裝置是通過accepted一個incoming connection來獲取的，而客戶端裝置則是通過開啟一個到伺服器的RFCOMM channel來獲取的。

伺服器端的實現

通過呼叫BluetoothAdapter的listenUsingRfcommWithServiceRecord(String, UUID)方法來獲取BluetoothServerSocket（UUID用於客戶端與伺服器端之間的配對）

呼叫BluetoothServerSocket的accept()方法監聽連線請求，如果收到請求，則返回一個BluetoothSocket例項（此方法為block方法，應置於新執行緒中）

如果不想在accept其他的連線，則呼叫BluetoothServerSocket的close()方法釋放資源（呼叫該方法後，之前獲得的BluetoothSocket例項並沒有close。但由於RFCOMM一個時刻只允許在一條channel中有一個連線，則一般在accept一個連線後，便close掉BluetoothServerSocket）

程式碼如下:
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) { }
    }
}

客戶端的實現
通過搜尋得到伺服器端的BluetoothService

呼叫BluetoothService的listenUsingRfcommWithServiceRecord(String, UUID)方法獲取BluetoothSocket（該UUID應該同於伺服器端的UUID）

呼叫BluetoothSocket的connect()方法（該方法為block方法），如果UUID同伺服器端的UUID匹配，並且連線被伺服器端accept，則connect()方法返回

注意：在呼叫connect()方法之前，應當確定當前沒有搜尋裝置，否則連線會變得非常慢並且容易失敗

程式碼如下:
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) { }
    }
}

連線管理（資料通訊）
分別通過BluetoothSocket的getInputStream()和getOutputStream()方法獲取InputStream和OutputStream

使用read(bytes[])和write(bytes[])方法分別進行讀寫操作

注意：read(bytes[])方法會一直block，知道從流中讀取到資訊，而write(bytes[])方法並不是經常的block（比如在另一裝置沒有及時read或者中間緩衝區已滿的情況下，write方法會block）

程式碼如下:
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) { }
    }
}

  除了這個常量，有提供其它的API，支援不同任務的其他常數。它們在下面列出。

Sr.No	常數說明
1	ACTION_REQUEST_DISCOVERABLE 此常數用於開啟藍芽的發現
2	ACTION_STATE_CHANGED 此常量將通知藍芽狀態已經改變
3	ACTION_FOUND 此常數用於接收關於所發現的每個裝置的資訊

啟用了藍芽功能之後，可以通過呼叫 getBondedDevices()方法來獲取配對裝置列表。它返回一組的藍芽裝置。其語法如下：

privateSet<BluetoothDevice>pairedDevices;
pairedDevices = BA.getBondedDevices();

除了配對的裝置，還有API，讓更多藍芽控制權等方法。它們在下面列出。

Sr.No	方法及說明
1	enable() 這種方法使介面卡，如果未啟用
2	isEnabled() 如果介面卡已啟用此方法返回true
3	disable() 該方法禁用介面卡
4	getName() 此方法返回的藍芽介面卡的名稱
5	setName(String name) 此方法更改藍芽名稱
6	getState() 此方法返回藍芽介面卡的當前狀態
7	startDiscovery() 此方法開始藍芽120秒的發現過程。