Android蓝牙开发详解

蓝牙传递数据是移动端经常使用的通信方式，Android中蓝牙模块依然很常用。本文就详细讲解Android蓝牙模块的使用方法。

       1、使用蓝牙的响应权限

XML/HTML代码

 <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代码

 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代码

 // 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代码

 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。

Java代码

 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代码

 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) { }
    }
 }

 

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