busquery.java

J2ME程序设计实例教程的源码

import java.io.*;
import javax.microedition.io.*;
import javax.microedition.lcdui.*;

public class BusQuery implements Runnable {
    private BQMIDlet midlet = null;
    private String serverURL = null;    //服务器定位符
    private String userAgent = null;    //客户端描述
    private HttpConnection hc = null;
    
    private byte[] queryCondition = new byte[0];      //查询条件
    private ProcessUI progress;
    private Thread queryThread;
    private boolean isAlive = true;
    private boolean forceStopQuery = false;
    
    public BusQuery(BQMIDlet bqmidlet, String serverURL) {
        this.midlet = bqmidlet;
        this.serverURL = serverURL;
        userAgent = "Profile:" + System.getProperty("microedition.profile") +
                     "\\Configuration:" + System.getProperty("microedition.configuration");
       
        progress = new ProcessUI("网络查询");
        progress.setCommandListener(new CommandListener() {
            public void commandAction(Command cmd, Displayable displayable) {
                stopQuery();
                midlet.backToMain();
            }
        });
    }
    
    //初始化查询线程
    public void init() {
        if(queryThread == null || !queryThread.isAlive()) {
            queryThread = new Thread(this);
            queryThread.start();
        }
    }
    
    //销毁查询线程
    public void release() {
        isAlive = false;
    }
    
    //停止查询
    public void stopQuery() {
        if(hc != null) {
            synchronized(hc) {
                try {
                    hc.close(); //关闭连接
                    forceStopQuery = true;
                }
                catch(IOException ioe) {
                    ioe.printStackTrace();
                }
            }
        }
    }
    
    public void setCondition(int type, String condition) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        try {
            dos.writeInt(type);
            dos.writeUTF(condition);
            queryCondition = baos.toByteArray();
        }
        catch(IOException ioe) {
            queryCondition = new byte[0];
            ioe.printStackTrace();
        }
    }
    
    public void execute() {
        if(queryCondition.length > 0) {
            synchronized(midlet) {
                midlet.notify();
            }
        }
    }
    
    public void run() {
        while(isAlive) {
            synchronized(midlet) {
                try {
                    midlet.wait();
                }
                catch(InterruptedException ie) {
                    ie.printStackTrace();
                }
            }
            
            if(isAlive) {
                try {
                    forceStopQuery = false;
                    progress.init();
                    midlet.setCurrent(progress);
                    progress.onProcess("正在连接服务器，发送查询请求...", 20);
                    //建立Http连接
                    hc = (HttpConnection)Connector.open(serverURL);
                    //设置请求方法\请求头属性
                    hc.setRequestMethod(HttpConnection.POST);
                    hc.setRequestProperty("User-Agent", userAgent);
                    hc.setRequestProperty("Content-type", "application/octet-stream");
                    hc.setRequestProperty("Content-length", "" + queryCondition.length);
                    //获取与连接相关的输出流，写出查询条件
                    OutputStream os = hc.openOutputStream();
                    os.write(queryCondition);
                    os.flush();
                    
                    //获得响应状态
                    int status = hc.getResponseCode();
                    if(status != HttpConnection.HTTP_OK) {
                        String msg = "网络连接错误！\n状态码：" +  status + "\n描述：\n " + hc.getResponseMessage();
                        throw new IOException(msg);
                    }
                    
                    //读取服务器的响应数据
                    DataInputStream dis = new DataInputStream(hc.openInputStream());
                    int size = dis.readInt();
                    Bus[] buses = new Bus[size];    
                    String name = null;
                    String stations = null;
                    System.out.println("size = " + size);
                    for(int i=0; i<size; i++) {
                        name = dis.readUTF();
                        stations = dis.readUTF();
                        buses[i] = new Bus(name, stations);
                        progress.onProcess("读取查询结果...", 20+70/size*i);
                    }
                    if(size > 0) {
                        midlet.showBuses(buses);
                    }
                    else {
                        midlet.showError("没有要查询的公交线路！");
                    }
                }
                catch(IOException ioe) {
                    if(!forceStopQuery) {
                        midlet.showError(ioe.getMessage());
                    }
                    else {
                        midlet.showError("用户取消查询。");
                    }
                }
                finally {
                    try {
                        if(hc != null) {
                            hc.close();
                        }
                    } 
                    catch(IOException ioe) {
                        ioe.printStackTrace();
                    }
                }
            }
        }
    }
}