Android蓝牙开发深入解析

1. 使用蓝牙的响应权限

 代码如下:

<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

 代码如下:

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）

Intent discoveryIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE); discoverableIntent.putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300);

//设置持续时间（最多300秒）

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

 代码如下:

// 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() + " " + 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）

 代码如下:

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

代码如下:

    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) { }

    }

}

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）

  代码如下:

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) { }

    }

}