Android 蓝牙开发实例解析

  在使用手机时,蓝牙通信给我们带来很多方便。那么在Android手机中怎样进行蓝牙开发呢?本文以实例的方式讲解Android蓝牙开发的知识。

  1、使用蓝牙的响应权限

  XML/HTML代码

  

  

  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)

  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。

  // 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)。

  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) { }

  }

  }

  5、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) { }

  }

  }

  以上就Android 蓝牙的开发简单示例代码,后续继续整理相关资料,谢谢大家对本站的支持!

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