Android 蓝牙开发浅析

fmms 7年前

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

    <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

    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

    // 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

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) { }            }        }  
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)

    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) { }            }        }  

转自:http://blog.csdn.net/gd920129/article/details/7487761