作者: 张奇
我将在这篇文章中介绍了的Android蓝牙程序。这个程序就是将实现把手机变做电脑PPT播放的遥控器:用音量加和音量减键来控制PPT页面的切换。
遥控器服务器端
首先,我们需要编写一个遥控器的服务器端(支持蓝牙的电脑)来接收手机端发出的信号。为了实现这个服务器端,我用到了一个叫做Bluecove(专门用来为蓝牙服务的!)的Java库。
以下是我的RemoteBluetoothServer类:
- <span style="font-size:16px;">public class RemoteBluetoothServer{
- public static void main(String[] args) {
- Thread waitThread = new Thread(new WaitThread());
- waitThread.start();
- }
- }
- </span>
在主方法中创建了一个线程,用于连接客户端,并处理信号。
- <span style="font-size:16px;">public class WaitThread implements Runnable{
- /** Constructor */
- public WaitThread() {
- }
- @Override
- public void run() {
- waitForConnection();
- }
- /** Waiting for connection from devices */
- private void waitForConnection() {
- // retrieve the local Bluetooth device object
- LocalDevice local = null;
- StreamConnectionNotifier notifier;
- StreamConnection connection = null;
- // setup the server to listen for connection
- try {
- local = LocalDevice.getLocalDevice();
- local.setDiscoverable(DiscoveryAgent.GIAC);
- UUID uuid = new UUID(80087355); // "04c6093b-0000-1000-8000-00805f9b34fb"
- String url = "btspp://localhost:" + uuid.toString() + ";name=RemoteBluetooth";
- notifier = (StreamConnectionNotifier)Connector.open(url);
- } catch (Exception e) {
- e.printStackTrace();
- return;
- }
- // waiting for connection
- while(true) {
- try {
- System.out.println("waiting for connection...");
- connection = notifier.acceptAndOpen();
- Thread processThread = new Thread(new ProcessConnectionThread(connection));
- processThread.start();
- } catch (Exception e) {
- e.printStackTrace();
- return;
- }
- }
- }
- }
- </span>
在waitForConnection()中,首先将服务器设为可发现的,并为这个程序创建了UUID(用于同客户端通信);然后就等待来自客户端的连接请求。当它收到一个初始的连接请求时,将创建一个ProcessConnectionThread来处理来自客户端的命令。以下是ProcessConnectionThread的代码:
- <span style="font-size:16px;">public class ProcessConnectionThread implements Runnable{
- private StreamConnection mConnection;
- // Constant that indicate command from devices
- private static final int EXIT_CMD = -1;
- private static final int KEY_RIGHT = 1;
- private static final int KEY_LEFT = 2;
- public ProcessConnectionThread(StreamConnection connection)
- {
- mConnection = connection;
- }
- @Override
- public void run() {
- try {
- // prepare to receive data
- InputStream inputStream = mConnection.openInputStream();
- System.out.println("waiting for input");
- while (true) {
- int command = inputStream.read();
- if (command == EXIT_CMD)
- {
- System.out.println("finish process");
- break;
- }
- processCommand(command);
- }
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- /**
- * Process the command from client
- * @param command the command code
- */
- private void processCommand(int command) {
- try {
- Robot robot = new Robot();
- switch (command) {
- case KEY_RIGHT:
- robot.keyPress(KeyEvent.VK_RIGHT);
- System.out.println("Right");
- break;
- case KEY_LEFT:
- robot.keyPress(KeyEvent.VK_LEFT);
- System.out.println("Left");
- break;
- }
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
- }
- </span>
ProcessConnectionThread类主要用于接收并处理客户端发送的命令。需要处理的命令只有两个:KEY_RIGHT和KEY_LEFT。我用java.awt.Robot来生成电脑端的键盘事件。
以上就是服务器端所需要做的工作。
遥控器客户端
这里的客户端指的其实就是Android手机。在开发手机端代码的过程中,我参考了 Android Dev Guide中Bluetooth Chat这个程序的代码,这个程序在SDK的示例代码中可以找到。
要将客户端连接服务器端,那么必须让手机可以扫描到电脑,DeviceListActivity 类的工作就是扫描并连接服务器。BluetoothCommandService类负责将命令传至服务器端。这两个类与Bluetooth Chat中的内容相似,只是删除了Bluetooth Chat中的BluetoothCommandService中的AcceptThread ,因为客户端不需要接受连接请求。ConnectThread用于初始化与服务器的连接,ConnectedThread 用于发送命令。
RemoteBluetooth 是客户端的主activity,其中主要代码如下:
- <span style="font-size:16px;">protected void onStart() {
- super.onStart();
- // If BT is not on, request that it be enabled.
- // setupCommand() will then be called during onActivityResult
- if (!mBluetoothAdapter.isEnabled()) {
- Intent enableIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
- startActivityForResult(enableIntent, REQUEST_ENABLE_BT);
- }
- // otherwise set up the command service
- else {
- if (mCommandService==null)
- setupCommand();
- }
- }
- private void setupCommand() {
- // Initialize the BluetoothChatService to perform bluetooth connections
- mCommandService = new BluetoothCommandService(this, mHandler);
- }
- </span>
onStart()用于检查手机上的蓝牙是否已经打开,如果没有打开则创建一个Intent来打开蓝牙。setupCommand()用于在按下音量加或音量减键时向服务器发送命令。其中用到了onKeyDown事件:
- <span style="font-size:16px;">public boolean onKeyDown(int keyCode, KeyEvent event) {
- if (keyCode == KeyEvent.KEYCODE_VOLUME_UP) {
- mCommandService.write(BluetoothCommandService.VOL_UP);
- return true;
- }
- else if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN){
- mCommandService.write(BluetoothCommandService.VOL_DOWN);
- return true;
- }
- return super.onKeyDown(keyCode, event);
- }
- </span>
此外,还需要在AndroidManifest.xml加入打开蓝牙的权限的代码。
- <span style="font-size:16px;"> <uses-permission android:name="android.permission.BLUETOOTH_ADMIN" />
- <uses-permission android:name="android.permission.BLUETOOTH" />
- </span>
以上就是客户端的代码。
将两个程序分别在电脑和手机上安装后,即可实现用手机当作一个PPT遥控器了!
参考文献:
http://developer.android.com/guide/topics/wireless/bluetooth.html
http://developer.android.com/resources/samples/BluetoothChat/index.html