Android蓝牙通信总结

浏览数：26 / 时间：2015年06月11日

这篇文章要达到的目标：

1.介绍在Android系统上实现蓝牙通信的过程中涉及到的概念。

2.在android系统上实现蓝牙通信的步骤。

3.在代码实现上的考虑。

4.例子代码实现(手持设备和蓝牙串口设备通信)。

1.介绍在Android系统上实现蓝牙通信的过程中使用到的类

BluetoothAdapter: Represents the local Bluetooth adapter (Bluetooth radio). The BluetoothAdapter is the entry-point for all Bluetooth interaction. Using this, you can discover other Bluetooth devices, query a list of bonded (paired) devices, instantiate a BluetoothDevice using a known MAC address, and create a BluetoothServerSocket to listen for communications from other devices.

BluetoothAdapter

代表当前手机的蓝牙设备。

BluetoothDevice: Represents a remote Bluetooth device. Use this to request a connection with a remote device through a BluetoothSocket or query information about the device such as its name, address, class, and bonding state.

代表要链接的蓝牙设备。通过这个类，用户就可以实现与两个蓝牙设备之间的链接(当前设备和被链接设备)。

BluetoothSocket: Represents the interface for a Bluetooth socket (similar to a TCP Socket). This is the connection point that allows an application to exchange data with another Bluetooth device via InputStream and OutputStream.

在蓝牙设备的通信中，某个服务，用一个唯一的UUID标识，比如串口通信服务(通过蓝牙实现串口通信)的UUID是:"00001101-0000-1000-8000-00805F9B34FB".

下述代码做的事情是：1.通过BluetoothDevice提供的方法，实现当前设备与目标设备的连接建立。2.使用1中获得的BluetoothSocket，进行实际的连接建立。3.然后，通过BluetoothSocket获取InputStream和OutputStream，就可以与目标设备进行通信；通过InputStream读取目标设备传递过来的信息；通过OutputStream，将数据写到目标设备。

private class ConnectThread extends Thread {
    private final BluetoothSocket mmSocket ;
    private final BluetoothDevice mmDevice ;

    public ConnectThread(BluetoothDevice device, boolean secure) {
      mmDevice = device;
      BluetoothSocket tmp = null ;
      // Get a BluetoothSocket for a connection with the
      // given BluetoothDevice
      try {

        tmp = device.createRfcommSocketToServiceRecord( MY_UUID );

      } catch (IOException e) {
        Log. e( TAG,e);
      }
      mmSocket = tmp;
    }

    public void run() {
      // Always cancel discovery because it will slow down a connection
      mAdapter.cancelDiscovery();
      try {
        mmSocket .connect();
      } catch (IOException e) {
        // Close the socket
        try {
          mmSocket .close();
        } catch (IOException e2) {
          Log. e( TAG,e2);
        }
        connectionFailed();
        return ;
      }
      synchronized (BluetoothService. this ) {
        mConnectThread = null ;
      }
      // Start the connected thread
      connected(mmSocket);
    }

    public void cancel() {
      try {
        mmSocket .close();
      } catch (IOException e) {
        Log. e( TAG, "close() of connect " + mSocketType + " socket failed", e);
      }
    }
  }

BluetoothServerSocket: Represents an open server socket that listens for incoming requests (similar to a TCP ServerSocket). In order to connect two Android devices, one device must open a server socket with this class. When a remote Bluetooth device makes a connection request to the this device, the BluetoothServerSocket will return a connected BluetoothSocket when the connection is accepted.

在蓝牙通信建立的过程中，初始化时，结构是Server/Client。Server端创建一个BluetoothServerSocket，专门监听Client端发出的请求，并对监听到的请求进行接收。成功接收后，返回一个BluetoothSocket给Client端。Client端，使用BluetoothSocket与Server端进行通信。

比如，手持设备和蓝牙串口通信设备通信，蓝牙串口设备是Server端，它监听来自Client端的链接请求。成功建立连接之后，Client端就可以与Server端进行通信。

在Server/Client架构中，一定有一端是Server端。

使用蓝牙进行双向通信时，则是连接的设备，既做Client端，又做Server端。

2.在android系统上实现蓝牙通信的步骤

1.setting up Bluetooth.

2.finding devices that are either paired or available in the local are.

3.connecting devices.

4.transferring data between devices.

3.代码实现上的考虑

1) 首先检查设备的的蓝牙是否可用。onCreate()方法。

2) 在蓝牙可用的基础下，检查蓝牙是否已经开启了;如果没有开启，则开启；如果开启了，则新建一个蓝牙通信服务。onStart()方法。

3) 在蓝牙通信服务开启(和可用)的基础下，检查当前的服务状态，如果是没有建立任何连接的，则选择要链接的设备(寻找已经配对的设备；首先要在蓝牙程序中进行设备的配对)，然后建立连接。onResume()方法。

4) 接下来就可以使用蓝牙通信服务进行数据传递mService;蓝牙数据的接收，mService会通过Handler传递给UI线程。

其中：3),选择要链接的设备，在下面的代码中，是这样做的，从已经配对的蓝牙设备中选择名称是DeviceName的蓝牙设备，然后建立连接。所以，首先要在系统的蓝牙管理程序中，先与指定的设备进行配对，这样，程序才可以在已经配对的设备中找到名称是DeviceName的蓝牙设备。

如下图：

状态转换顺序:

onCreate()---->onStart()，如果没有启用，则进行启用----->onPause()---->onResume()

onCreate()---->onStart(),如果蓝牙已经启用了，则---->onResume().

public class MainActivity extends Activity implements View.OnClickListener {

  private BluetoothAdapter mBluetoothAdapter = null;
  private BluetoothService mService = null;
  private BluetoothDevice mOnePairedDevice;
  private final String DeviceName = "LILEI" ;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout. activity_main);

    mBluetoothAdapter = BluetoothAdapter. getDefaultAdapter();
    if ( mBluetoothAdapter == null ) {

      Toast.makeText(this, "Bluetooth is not available", Toast.LENGTH_LONG ).show();
      finish();
    }
    ....
    }

  @Override
  public void onStart() {
    super.onStart();

    if (! mBluetoothAdapter.isEnabled()) {
      // Enable Bluetooth function
      Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE );
      startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
    } else if (mService == null) {
      setupBluetoothService();
    }
  }

  @Override
  public void onResume() {
    super.onResume();

    // Performing this check in onResume() covers the case in which BT was
    // not enabled during onStart(), so we were paused to enable it...
    // onResume() will be called when ACTION_REQUEST_ENABLE activity returns.
    if ( mService != null ) {
      // Only if the state is STATE_NONE, do we know that we haven‘t started already
      if ( mService.getState() == BluetoothService.STATE_NONE) {
        if (mOnePairedDevice == null) {
          mOnePairedDevice = getASpecificPairedDevice(DeviceName );
        }
        if (mOnePairedDevice != null) {
          mService.start(mOnePairedDevice );
        } else {
          Toast. makeText(this, "Not Found the paired Device." , Toast.LENGTH_LONG ).show();
        }

      }
    }
  }

  @Override
  public void onDestroy() {
    super.onDestroy();
    if ( mService != null ) {
      mService.stop();
    }
  }

  @Override
  public void onActivityResult(int requestCode, int resultCode, Intent data) {
    switch (requestCode) {

      case REQUEST_ENABLE_BT:
        // When the request to enable Bluetooth returns
        if (resultCode == Activity.RESULT_OK) {
          setupBluetoothService();
        } else {
          // User did not enable Bluetooth or an error occurred
          Log. d(TAG, "BT not enabled");
          Toast. makeText(this, R.string. bt_not_enabled_leaving, Toast.LENGTH_SHORT ).show();
          finish();
        }
    }
  }

  public void setupBluetoothService() {
    mService = new BluetoothService(mHandler );
  }
     
  private BluetoothDevice getASpecificPairedDevice(String name) {
    Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices();
    // If there are paired devices
    if (pairedDevices.size() > 0) {
      // Loop through paired devices
      for (BluetoothDevice device : pairedDevices) {
        if (name.equals(device.getName())) {
          return device;
        }
      }

    }

    return null;
  }
    ...
   }

4.例子代码实现

在确定了蓝牙可用，蓝牙开启，要链接的设备，这些信息之后，就可以建立连接，然后进行通信管理。

下述代码的实现：

1.当前服务的状态标识---有这种。根据状态标识执行不同的操作。

2.ConnectedThread线程，会不断循环读取InputStream，即是读取连接设备传递过来的信息，若有信息，则通过Handler传递给UI线程；当要对连接设备传递信息的时候，调用ConnectedThread暴露的public方法，write( byte [] buffer),writeFileMessage( byte [] buffer),writeFileStream(InputStream input).传递信息给连接设备时，使用OutputStream。

要关闭与连接设备的通信，则调用暴露方法cancle(),即是调用BluetoothSocket的close()方法。

3.在初始化服务时，使用ConnectThread来建立与目标设备的链接，获取BluetoothSocket.因为BluetoothSocket的connect方法是阻塞的，所以在独立的线程中执行,避免阻塞UI线程。

服务的状态变化：

初始化时，STATE_NONE;执行建立连接的操作时，STATE_CONNECTING；当已经和链接设备建立连接了，即是获取了BluetoothSocket，则标注状态STATE_CONNECTED；

停止连接线程，读写线程之后，则标注状态为STATE_NONE。

public class BluetoothService {

    private static final String TAG = "BluetoothService" ;
    private static final UUID MY_UUID = UUID.fromString( "00001101-0000-1000-8000-00805F9B34FB");

    // Constants that indicate the current connection state
    public static final int STATE_NONE = 0; // we‘re doing nothing
    public static final int STATE_LISTEN = 1; // now listening for incoming connections
    public static final int STATE_CONNECTING = 2; // now initiating an outgoing connection
    public static final int STATE_CONNECTED = 3; // now connected to a remote device

    private final BluetoothAdapter mAdapter ;
    private Handler mHandler ;

    private ConnectThread mConnectThread ;
    private ConnectedThread mConnectedThread ;

    private int mState ;

    public BluetoothService(Handler handler) {
        mAdapter = BluetoothAdapter.getDefaultAdapter();
        mHandler = handler;

        mState = STATE_NONE ;

    }

    public void setHandler(Handler handler) {
        mHandler = handler;
    }

    public void start(BluetoothDevice remoteDevice) {
        connect(remoteDevice, false );
    }

    public int getState() {
        return mState ;
    }

    public void stop() {
        Log. d( TAG, "stop" );

        if (mConnectThread != null) {
            mConnectThread .cancel();
            mConnectThread = null ;
        }

        if (mConnectedThread != null) {
            mConnectedThread .cancel();
            mConnectedThread = null ;
        }
        setState( STATE_NONE );

    }

    /**
     * This thread runs while attempting to make an outgoing connection with a device. It runs
     * straight through; the connection either succeeds or fails.
     */
    private class ConnectThread extends Thread {
        private final BluetoothSocket mmSocket;
        private final BluetoothDevice mmDevice;
        private String mSocketType ;

        public ConnectThread(BluetoothDevice device, boolean secure) {
            mmDevice = device;
            BluetoothSocket tmp = null ;
            mSocketType = secure ? "Secure" : "Insecure";

            // Get a BluetoothSocket for a connection with the
            // given BluetoothDevice
            try {

                tmp = device.createRfcommSocketToServiceRecord( MY_UUID );

            } catch (IOException e) {
                Log. e( TAG, "Socket Type: " + mSocketType + "create() failed", e);
            }
            mmSocket = tmp;
        }

        public void run() {
            Log. i( TAG, "BEGIN mConnectThread SocketType:" + mSocketType );
            setName( "ConnectThread" + mSocketType );

            // Always cancel discovery because it will slow down a connection
            mAdapter .cancelDiscovery();

            // Make a connection to the BluetoothSocket
            try {
                // This is a blocking call and will only return on a
                // successful connection or an exception
                mmSocket .connect();
            } catch (IOException e) {
                // Close the socket
                try {
                    mmSocket .close();
                } catch (IOException e2) {
                    Log. e( TAG, "unable to close() " + mSocketType
                            + " socket during connection failure" , e2);
                }
                connectionFailed();
                return ;
            }

            // Reset the ConnectThread because we‘re done
            synchronized (BluetoothService. this) {
                mConnectThread = null ;
            }

            // Start the connected thread
            connected( mmSocket , mmDevice , mSocketType );
        }

        public void cancel() {
            try {
                mmSocket .close();
            } catch (IOException e) {
                Log. e( TAG, "close() of connect " + mSocketType + " socket failed", e);
            }
        }
    }

    /**
     * Indicate that the connection attempt failed and notify the UI Activity.
     */
    private void connectionFailed() {
        // Send a failure message back to the Activity
        Message msg = mHandler .obtainMessage(Constants. MESSAGE_TOAST);
        Bundle bundle = new Bundle();
        bundle.putString(Constants. TOAST , "Unable to connect device" );
        msg.setData(bundle);
        mHandler .sendMessage(msg);

    }

    /**
     * Set the current state of the chat connection
     *
     * @param state An integer defining the current connection state
     */
    private synchronized void setState( int state) {
        Log. d( TAG, "setState() " + mState + " -> " + state);
        mState = state;

        // Give the new state to the Handler so the UI Activity can update
        mHandler .obtainMessage(Constants. MESSAGE_STATE_CHANGE, state, -1).sendToTarget();
    }

    /**
     * Start the ConnectedThread to begin managing a Bluetooth connection
     *
     * @param socket The BluetoothSocket on which the connection was made
     * @param device The BluetoothDevice that has been connected
     */
    public synchronized void connected(BluetoothSocket socket, BluetoothDevice device,
            final String socketType) {
        Log. d( TAG, "connected, Socket Type:" + socketType);

        // Cancel the thread that completed the connection
        if (mConnectThread != null) {
            mConnectThread .cancel();
            mConnectThread = null ;
        }

        // Cancel any thread currently running a connection
        if (mConnectedThread != null) {
            mConnectedThread .cancel();
            mConnectedThread = null ;
        }

        // Start the thread to manage the connection and perform transmissions
        mConnectedThread = new ConnectedThread(socket, socketType);
        mConnectedThread .start();

        // Send the name of the connected device back to the UI Activity
        Message msg = mHandler .obtainMessage(Constants. MESSAGE_DEVICE_NAME);
        Bundle bundle = new Bundle();
        bundle.putString(Constants. DEVICE_NAME , device.getName());
        msg.setData(bundle);
        mHandler .sendMessage(msg);

        setState( STATE_CONNECTED );
    }

    /**
     * This thread runs during a connection with a remote device. It handles all incoming and
     * outgoing transmissions.
     */
    private class ConnectedThread extends Thread {
        private final BluetoothSocket mmSocket;
        private final InputStream mmInStream;
        private final OutputStream mmOutStream;

        public ConnectedThread(BluetoothSocket socket, String socketType) {
            Log. d( TAG, "create ConnectedThread: " + socketType);
            mmSocket = socket;
            InputStream tmpIn = null ;
            OutputStream tmpOut = null ;

            // Get the BluetoothSocket input and output streams
            try {
                tmpIn = socket.getInputStream();
                tmpOut = socket.getOutputStream();
            } catch (IOException e) {
                Log. e( TAG, "temp sockets not created" , e);
            }

            mmInStream = tmpIn;
            mmOutStream = tmpOut;
        }

        public void run() {
            Log. i( TAG, "BEGIN mConnectedThread" );
            byte [] buffer = new byte[3024];
            int bytes;

            // Keep listening to the InputStream while connected
            while (true ) {
                try {
                    // Read from the InputStream
                    bytes = mmInStream .read(buffer);

                    // Send the obtained bytes to the UI Activity
                    mHandler .obtainMessage(Constants. MESSAGE_READ, bytes, -1, buffer)
                            .sendToTarget();
                } catch (IOException e) {
                    Log. e( TAG, "disconnected" , e);
                    connectionLost();

                    break ;
                }
            }
        }

        /**
         * Write to the connected OutStream.
         *
         * @param buffer The bytes to write
         */
        public void write( byte[] buffer) {
            try {
                mmOutStream .write(buffer);

                // Share the sent message back to the UI Activity
                mHandler .obtainMessage(Constants. MESSAGE_WRITE, -1, -1, buffer).sendToTarget();
            } catch (IOException e) {
                Log. e( TAG, "Exception during write" , e);
            }
        }

        public void writeFileMessage( byte[] buffer) {
            try {
                mmOutStream .write(buffer);
            } catch (IOException e) {
                Log. e( TAG, "Exception during write" , e);
            }
        }

        public void writeFileStream (InputStream input) {
            byte [] buffer = new byte[1024];
            int readLengh;
            try {
                while ((readLengh = input.read(buffer)) != -1) {
                    mmOutStream .write(buffer, 0, readLengh);
                }
                mHandler
                        .obtainMessage(Constants. MESSAGE_WRITE , -1, -1,
                                "Finish send file to remoteDevice." )
                        .sendToTarget();

            } catch (IOException e) {
                Log. e( TAG, "Exception during write" , e);
                mHandler .obtainMessage(Constants. MESSAGE_WRITE, -1, -1,
                        "Error when send file to remoteDevice").sendToTarget();
            }

        }

        public void cancel() {
            try {
                mmSocket .close();
            } catch (IOException e) {
                Log. e( TAG, "close() of connect socket failed" , e);
            }
        }
    }

    /**
     * Indicate that the connection was lost and notify the UI Activity.
     */
    private void connectionLost() {
        // Send a failure message back to the Activity
        Message msg = mHandler .obtainMessage(Constants. MESSAGE_TOAST);
        Bundle bundle = new Bundle();
        bundle.putString(Constants. TOAST , "Device connection was lost" );
        msg.setData(bundle);
        mHandler .sendMessage(msg);

        // Start the service over to restart listening mode

    }

    /**
     * Start the ConnectThread to initiate a connection to a remote device.
     *
     * @param device The BluetoothDevice to connect
     * @param secure Socket Security type - Secure (true) , Insecure (false)
     */
    public synchronized void connect(BluetoothDevice device, boolean secure) {
        Log. d( TAG, "connect to: " + device);

        // Cancel any thread attempting to make a connection
        if (mState == STATE_CONNECTING) {
            if (mConnectThread != null) {
                mConnectThread .cancel();
                mConnectThread = null ;
            }
        }

        // Cancel any thread currently running a connection
        if (mConnectedThread != null) {
            mConnectedThread .cancel();
            mConnectedThread = null ;
        }

        // Start the thread to connect with the given device
        mConnectThread = new ConnectThread(device, secure);
        mConnectThread .start();
        setState( STATE_CONNECTING );
    }

    /**
     * Write to the ConnectedThread in an unsynchronized manner
     *
     * @param out The bytes to write
     * @see ConnectedThread#write(byte[])
     */
    public void write( byte[] out, boolean isFile) {
        // Create temporary object
        ConnectedThread r;
        // Synchronize a copy of the ConnectedThread
        synchronized (this ) {
            if (mState != STATE_CONNECTED)
                return ;
            r = mConnectedThread ;
        }
        // Perform the write unsynchronized
        if (isFile) {
            r.writeFileMessage(out);
        } else {
            r.write(out);
        }

    }

    public void write(InputStream in) {
        // Create temporary object
        ConnectedThread r;
        // Synchronize a copy of the ConnectedThread
        synchronized (this ) {
            if (mState != STATE_CONNECTED)
                return ;
            r = mConnectedThread ;
        }
        // Perform the write unsynchronized
        r. writeFileStream(in);
    }
}