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,假如目标平台支持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把握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,预备发送请求");
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;
}
}
//假如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();
}
}
}
}
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