J2ME蓝牙实战入门

作者：陈万飞 文章来源：JavaResearch

概述

    目前，很多手机已经具备了蓝牙功能。虽然MIDP2.0没有包括蓝牙API,但是JCP定义了JSR82, Java APIs for Bluetooth Wireless Technology (JABWT).这是一个可选API,很多支持MIDP2.0的手机已经实现了，比如Nokia 6600, Nokia 6670，Nokia7610等等。对于一个开发者来说,如果目标平台支持JSR82的话，在制作联网对战类型游戏或者应用的时候，蓝牙是一个相当不错的选择。本文给出了一个最简单的蓝牙应用的J2ME程序，用以帮助开发者快速的掌握JSR82。该程序分别在2台蓝牙设备上安装后，一台设备作为服务端先运行，一台设备作为客户端后运行。在服务端上我们发布了一个服务，该服务的功能是把客户端发过来的字符串转变为大写字符串。客户端起动并搜索到服务端的服务后，我们就可以从客户端的输入框里输入任意的字符串，发送到服务端去，同时观察服务端的反馈结果。
    本文并不具体讲述蓝牙的运行机制和JSR82的API结构，关于这些知识点，请参考本文的参考资料一节，这些参考资料会给你一个权威的精确的解释。

实例代码

    该程序包括3个java文件。一个是MIDlet,另外2个为服务端GUI和客户端GUI。该程序已经在wtk22模拟器和Nokia 6600,Nokia 6670两款手机上测试通过。

StupidBTMIDlet.java

import javax.microedition.lcdui.Alert;
import javax.microedition.lcdui.AlertType;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Display;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.List;
import javax.microedition.midlet.MIDlet;
import javax.microedition.midlet.MIDletStateChangeException;

/**
 * @author Jagie
 * 
 *  MIDlet
 */
public class StupidBTMIDlet extends MIDlet implements CommandListener {
    List list;

    ServerBox sb;

    ClientBox cb;

    /*
     * (non-Javadoc)
     * 
     * @see javax.microedition.midlet.MIDlet#startApp()
     */
    protected void startApp() throws MIDletStateChangeException {
        list = new List("傻瓜蓝牙入门", List.IMPLICIT);
        list.append("Client", null);
        list.append("Server", null);
        list.setCommandListener(this);
        Display.getDisplay(this).setCurrent(list);

    }
    
    /**
     * debug方法
     * @param s 要显示的字串
     */

    public void showString(String s) {
        Displayable dp = Display.getDisplay(this).getCurrent();
        Alert al = new Alert(null, s, null, AlertType.INFO);
        al.setTimeout(2000);
        Display.getDisplay(this).setCurrent(al, dp);
    }
    
    /**
     * 显示主菜单
     *
     */

    public void showMainMenu() {
        Display.getDisplay(this).setCurrent(list);
    }

    
    protected void pauseApp() {
        // TODO Auto-generated method stub

    }

    public void commandAction(Command com, Displayable disp) {
        if (com == List.SELECT_COMMAND) {
            List list = (List) disp;
            int index = list.getSelectedIndex();
            if (index == 1) {
                if (sb == null) {
                    sb = new ServerBox(this);
                }
                sb.setString(null);
                Display.getDisplay(this).setCurrent(sb);
            } else {
                //每次都生成新的客户端实例
                cb = null;
                System.gc();
                cb = new ClientBox(this);

                Display.getDisplay(this).setCurrent(cb);
            }
        }
    }

    protected void destroyApp(boolean arg0) throws MIDletStateChangeException {
        // TODO Auto-generated method stub

    }

}

ClientBox.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import java.util.Vector;

import javax.microedition.io.Connector;
import javax.microedition.io.StreamConnection;
import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Displayable;
import javax.microedition.lcdui.Form;
import javax.microedition.lcdui.Gauge;
import javax.microedition.lcdui.StringItem;
import javax.microedition.lcdui.TextField;

//jsr082 API
import javax.bluetooth.BluetoothStateException;

import javax.bluetooth.DeviceClass;
import javax.bluetooth.DiscoveryAgent;
import javax.bluetooth.DiscoveryListener;
import javax.bluetooth.LocalDevice;
import javax.bluetooth.RemoteDevice;
import javax.bluetooth.ServiceRecord;
import javax.bluetooth.UUID;

/**
 * 客户端GUI
 * @author Jagie
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class ClientBox extends Form implements Runnable, CommandListener,
        DiscoveryListener {

    
    //字串输入框
    TextField input = new TextField(null, "", 50, TextField.ANY);
    //loger
    StringItem result = new StringItem("结果:", "");

    private DiscoveryAgent discoveryAgent;

    
    private UUID[] uuidSet;

    //响应服务的UUID
    private static final UUID ECHO_SERVER_UUID = new UUID(
            "F0E0D0C0B0A000908070605040302010", false);

    //设备集合
    Vector devices = new Vector();
    //服务集合
    Vector records = new Vector();
    
    //服务搜索的事务id集合
    int[] transIDs;
    StupidBTMIDlet midlet;

    public ClientBox(StupidBTMIDlet midlet) {
        super("");
        this.midlet=midlet;
        
        this.append(result);
        
        this.addCommand(new Command("取消",Command.CANCEL,1));
        this.setCommandListener(this);
        
        new Thread(this).start();
    }
    
    public void commandAction(Command arg0, Displayable arg1) {
        if(arg0.getCommandType()==Command.CANCEL){
            midlet.showMainMenu();
        }else{
            //匿名内部Thread，访问远程服务。
            Thread fetchThread=new Thread(){
                public void run(){
                    for(int i=0;i<records.size();i++){
                        ServiceRecord sr=(ServiceRecord)records.elementAt(i);
                        if(accessService(sr)){
                            //访问到一个可用的服务即可
                            break;
                        }
                    }
                }
            };
            fetchThread.start();
        }
        
    }
    
    
    private boolean  accessService(ServiceRecord sr){
        boolean result=false;
         try {
            String url = sr.getConnectionURL(
                    ServiceRecord.NOAUTHENTICATE_NOENCRYPT, false);
            StreamConnection    conn = (StreamConnection) Connector.open(url);
            
            DataOutputStream dos=conn.openDataOutputStream();
            dos.writeUTF(input.getString());
            dos.close();
            DataInputStream dis=conn.openDataInputStream();
            String echo=dis.readUTF();
            dis.close();
            showInfo("反馈结果是:"+echo);
            result=true;
            
        } catch (IOException e) {
            
        }
        return result;
    }

    public synchronized void run() {
        //发现设备和服务的过程中，给用户以Gauge
        Gauge g=new Gauge(null,false,Gauge.INDEFINITE,Gauge.CONTINUOUS_RUNNING);
        this.append(g);
        showInfo("蓝牙初始化...");
        boolean isBTReady = false;

        try {

            LocalDevice localDevice = LocalDevice.getLocalDevice();
            discoveryAgent = localDevice.getDiscoveryAgent();

            isBTReady = true;
        } catch (Exception e) {
            e.printStackTrace();
        }

        if (!isBTReady) {
            showInfo("蓝牙不可用");
            //删除Gauge
            this.delete(1);
            return;
        }

        uuidSet = new UUID[2];

        //标志我们的响应服务的UUID集合
        uuidSet[0] = new UUID(0x1101);
        uuidSet[1] = ECHO_SERVER_UUID;

        
        try {
            discoveryAgent.startInquiry(DiscoveryAgent.GIAC, this);
        } catch (BluetoothStateException e) {

        }

        try {
            //阻塞,由inquiryCompleted()回调方法唤醒
            wait();
        } catch (InterruptedException e1) {
            
            e1.printStackTrace();
        }
        showInfo("设备搜索完毕,共找到"+devices.size()+"个设备,开始搜索服务");
        transIDs = new int[devices.size()];
        for (int i = 0; i < devices.size(); i++) {
            RemoteDevice rd = (RemoteDevice) devices.elementAt(i);
            try {
                //记录每一次服务搜索的事务id
                transIDs[i] = discoveryAgent.searchServices(null, uuidSet,
                        rd, this);
            } catch (BluetoothStateException e) {
                continue;
            }

        }
        
        try {
            //阻塞,由serviceSearchCompleted()回调方法在所有设备都搜索完的情况下唤醒
            wait();
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
        
        showInfo("服务搜索完毕,共找到"+records.size()+"个服务,准备发送请求");
        if(records.size()>0){
            this.append(input);
            this.addCommand(new Command("发送",Command.OK,0));
        }
        
        //删除Gauge
        this.delete(1);
        
    }
    
    /**
     * debug
     * @param s
     */
    
    private void showInfo(String s){
        StringBuffer sb=new StringBuffer(result.getText());
        if(sb.length()>0){
            sb.append("/n");
        }
        sb.append(s);
        result.setText(sb.toString());

    }
    
    /**
     * 回调方法
     */

    public void deviceDiscovered(RemoteDevice btDevice, DeviceClass cod) {

        if (devices.indexOf(btDevice) == -1) {
            devices.addElement(btDevice);
        }
    }

    /**
     * 回调方法，唤醒初始化线程
     */
    public void inquiryCompleted(int discType) {

        synchronized (this) {
            notify();
        }
    }
    /**
     * 回调方法
     */
    public void servicesDiscovered(int transID, ServiceRecord[] servRecord) {
        for (int i = 0; i < servRecord.length; i++) {
            records.addElement(servRecord[i]);
        }
    }
    
    /**
     * 回调方法，唤醒初始化线程
     */

    public void serviceSearchCompleted(int transID, int respCode) {
        
        for (int i = 0; i < transIDs.length; i++) {
            if (transIDs[i] == transID) {
                transIDs[i] = -1;
                break;
            }
        }
        
        //如果所有的设备都已经搜索服务完毕，则唤醒初始化线程。

        boolean finished = true;
        for (int i = 0; i < transIDs.length; i++) {
            if (transIDs[i] != -1) {
                finished = false;
                break;
            }
        }

        if (finished) {
            synchronized (this) {
                notify();
            }
        }

    }

}

ServerBox.java

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;

import java.util.Vector;

import javax.bluetooth.DiscoveryAgent;
import javax.bluetooth.LocalDevice;
import javax.bluetooth.ServiceRecord;
import javax.bluetooth.UUID;
import javax.microedition.io.Connector;
import javax.microedition.io.StreamConnection;
import javax.microedition.io.StreamConnectionNotifier;

import javax.microedition.lcdui.Command;
import javax.microedition.lcdui.CommandListener;
import javax.microedition.lcdui.Displayable;

import javax.microedition.lcdui.TextBox;
import javax.microedition.lcdui.TextField;

/**
 * 服务端GUI
 * @author Jagie
 *
 * TODO To change the template for this generated type comment go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
public class ServerBox extends TextBox implements Runnable, CommandListener {

    Command com_pub = new Command("开启服务", Command.OK, 0);

    Command com_cancel = new Command("终止服务", Command.CANCEL, 0);

    Command com_back = new Command("返回", Command.BACK, 1);

    LocalDevice localDevice;

    StreamConnectionNotifier notifier;

    ServiceRecord record;

    boolean isClosed;

    ClientProcessor processor;

    StupidBTMIDlet midlet;
    //响应服务的uuid
    private static final UUID ECHO_SERVER_UUID = new UUID(
            "F0E0D0C0B0A000908070605040302010", false);

    public ServerBox(StupidBTMIDlet midlet) {
        super(null, "", 500, TextField.ANY);
        this.midlet = midlet;
        this.addCommand(com_pub);
        this.addCommand(com_back);
        this.setCommandListener(this);
    }

    public void run() {
        boolean isBTReady = false;

        try {

            localDevice = LocalDevice.getLocalDevice();

            if (!localDevice.setDiscoverable(DiscoveryAgent.GIAC)) {
                showInfo("无法设置设备发现模式");
                return;
            }

            // prepare a URL to create a notifier
            StringBuffer url = new StringBuffer("btspp://");

            // indicate this is a server
            url.append("localhost").append(':');

            // add the UUID to identify this service
            url.append(ECHO_SERVER_UUID.toString());

            // add the name for our service
            url.append(";name=Echo Server");

            // request all of the client not to be authorized
            // some devices fail on authorize=true
            url.append(";authorize=false");

            // create notifier now
            notifier = (StreamConnectionNotifier) Connector
                    .open(url.toString());

            record = localDevice.getRecord(notifier);

            // remember we've reached this point.
            isBTReady = true;
        } catch (Exception e) {
            e.printStackTrace();
            
        }

        // nothing to do if no bluetooth available
        if (isBTReady) {
            showInfo("初始化成功，等待连接");
            this.removeCommand(com_pub);
            this.addCommand(com_cancel);
        } else {
            showInfo("初始化失败,退出");
            return;

        }

        // 生成服务端服务线程对象
        processor = new ClientProcessor();

        // ok, start accepting connections then
        while (!isClosed) {
            StreamConnection conn = null;

            try {
                conn = notifier.acceptAndOpen();
            } catch (IOException e) {
                // wrong client or interrupted - continue anyway
                continue;
            }
            processor.addConnection(conn);
        }

    }

    public void publish() {
        isClosed = false;
        this.setString(null);
        new Thread(this).start();

    }

    public void cancelService() {
        isClosed = true;
        showInfo("服务终止");
        this.removeCommand(com_cancel);
        this.addCommand(com_pub);
    }

    /*
     * (non-Javadoc)
     * 
     * @see javax.microedition.lcdui.CommandListener#commandAction(javax.microedition.lcdui.Command,
     *      javax.microedition.lcdui.Displayable)
     */
    public void commandAction(Command arg0, Displayable arg1) {
        if (arg0 == com_pub) {
            //发布service
            publish();
        } else if (arg0 == com_cancel) {
            cancelService();
        } else {
            cancelService();
            midlet.showMainMenu();
        }

    }
    
    /**
     * 内部类，服务端服务线程。
     * @author Jagie
     *
     * TODO To change the template for this generated type comment go to
     * Window - Preferences - Java - Code Style - Code Templates
     */
    private class ClientProcessor implements Runnable {
        private Thread processorThread;

        private Vector queue = new Vector();

        private boolean isOk = true;

        ClientProcessor() {
            processorThread = new Thread(this);
            processorThread.start();
        }

        public void run() {
            while (!isClosed) {

                synchronized (this) {
                    if (queue.size() == 0) {
                        try {
                            //阻塞，直到有新客户连接
                            wait();
                        } catch (InterruptedException e) {

                        }
                    }
                }
                
                //处理连接队列

                StreamConnection conn;

                synchronized (this) {

                    if (isClosed) {
                        return;
                    }
                    conn = (StreamConnection) queue.firstElement();
                    queue.removeElementAt(0);
                    processConnection(conn);
                }
            }
        }
        
        /**
         * 往连接队列添加新连接，同时唤醒处理线程
         * @param conn
         */

        void addConnection(StreamConnection conn) {
            synchronized (this) {
                queue.addElement(conn);
                notify();
            }
        }

    }

    /**
     * 从StreamConnection读取输入
     * @param conn
     * @return
     */
    private String readInputString(StreamConnection conn) {
        String inputString = null;

        try {

            DataInputStream dis = conn.openDataInputStream();
            inputString = dis.readUTF();
            dis.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return inputString;
    }
    
    /**
     * debug
     * @param s
     */

    private void showInfo(String s) {
        StringBuffer sb = new StringBuffer(this.getString());
        if (sb.length() > 0) {
            sb.append("/n");
        }

        sb.append(s);
        this.setString(sb.toString());

    }
    

    /**
     * 处理客户端连接
     * @param conn
     */    
    private void processConnection(StreamConnection conn) {

        // 读取输入
        String inputString = readInputString(conn);
        //生成响应
        String outputString = inputString.toUpperCase();
        //输出响应
        sendOutputData(outputString, conn);

        try {
            conn.close();
        } catch (IOException e) {
        } // ignore
        showInfo("客户端输入:" + inputString + ",已成功响应!");
    }
    
    /**
     * 输出响应
     * @param outputData
     * @param conn
     */

    private void sendOutputData(String outputData, StreamConnection conn) {

        try {
            DataOutputStream dos = conn.openDataOutputStream();
            dos.writeUTF(outputData);
            dos.close();
        } catch (IOException e) {
        }

    }
}

小结

    本文给出了一个简单的蓝牙服务的例子。旨在帮助开发者快速掌握JSR82.如果该文能对你有所启发,那就很好了。

参考资料

1. http://developers.sun.com/techtopics/mobility/apis/articles/bluetoothintro/
  JSR82 API介绍(英文)
2. /Article/ShowArticle.asp?ArticleID=249
  JSR82 API 介绍(中文)
3. http://www.jcp.org/en/jsr/detail?id=82
  JSR82 Specification.
4.WTK22, BluetoothDemo 项目