gpsreader.java

这为GPS开发过程源代码,希望对各位有所帮助,

/*****************************************************************************

 Description: This class is used to read the data from a GPS receiver using the NMEA protocol.

 Created By: Oscar Vivall 2005-06-28
 
 @file        GPSReader.java

 COPYRIGHT All rights reserved Sony Ericsson Mobile Communications AB 2004.
 The software is the copyrighted work of Sony Ericsson Mobile Communications AB.
 The use of the software is subject to the terms of the end-user license 
 agreement which accompanies or is included with the software. The software is 
 provided "as is" and Sony Ericsson specifically disclaim any warranty or 
 condition whatsoever regarding merchantability or fitness for a specific 
 purpose, title or non-infringement. No warranty of any kind is made in 
 relation to the condition, suitability, availability, accuracy, reliability, 
 merchantability and/or non-infringement of the software provided herein.

*****************************************************************************/

import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;

import javax.microedition.io.*;

import java.io.*;
import java.util.*;

public class GPSReader implements Runnable{

    private String url = "";
    
    // This is the data retreived from the GPS
    public static double SPEED_KMH = 0;
    public static String SPEED_KMH_STR = "";
    public static int NUM_SATELITES = 0;
    public static String NUM_SATELITES_STR = "";
    
    private String []result = new String[25];
    
    private Vector speedVector = new Vector();
    
    public static String TYPE=""; // Used for debugging.
    private String exc = ""; // Used for debugging.

    // Array used to interpolate the speed.
    private String []sp = new String[9];
    private int spIndex = 0;
    
    /*
     * The url to the bluetooth device is the String parameter.
    */
    public GPSReader(String u){
        url = u; // Connection string to the bluetooth device.
        Thread t = new Thread(this);
        t.start();
    }

    public void run() {

        StreamConnection conn = null;
        InputStream is = null;
        String err = ""; // used for debugging
        
        try{
            conn = (StreamConnection)Connector.open(url);
            is = conn.openInputStream();

            int i=0;
            char c;
            String s = "";
            String []data;
            String DATA_STRING;

            // Start reading the data from the GPS
            do{
                i = is.read(); // read one byte at the time.
                c = (char)i;
                s += c;
                if(i==36){ // Every sentence starts with a '$'
                    if(s.length()>5){
                        DATA_STRING = s.substring(5, s.length());
                        TYPE = s.substring(2, 5);

                        // Check the gps data type and convert the information to a more readable format.
                        if(s.substring(0, 5).compareTo("GPGGA") == 0){
                            try{
                                data = splitString(DATA_STRING);

                                NUM_SATELITES_STR = data[6];
                                NUM_SATELITES = Integer.parseInt(data[6]);
                                exc = "";
                            }catch(Exception e){
                                exc = "<GGA>" + e.getMessage();
                                NUM_SATELITES = 0;
                            }

                        }else if(s.substring(0, 5).compareTo("GPVTG") == 0){
                            try{
                                data = splitString(DATA_STRING);

                                SPEED_KMH_STR = data[6];

                                speedVector.addElement(data[6]);
                                spIndex = spIndex==8?0:spIndex+1;

                                if(speedVector.size()==10){
                                    speedVector.removeElementAt(0);
                                }
                                double tot =0;
                                String tmp = "";

                                for(int n=0; n<speedVector.size(); n++){
                                    tmp  = (String)speedVector.elementAt(n);
                                    exc = "";
                                    try{
                                        tot += Double.parseDouble(tmp);
                                    }catch(Exception e){
                                        exc = "<VTG>" + e.getMessage();
                                        tot +=0;
                                    }
                                }
                                SPEED_KMH = tot/(double)speedVector.size();

                            }catch(Exception e){
                                SPEED_KMH = 0;
                            }
                        }
                    }

                    TYPE +=  ":" + exc;
                    s = "";
                }
            }while(i != -1);

        }catch(Exception e){
            err = e.toString();
            System.out.println(e);
        }
        TYPE = "EXITED!! : " + err;
    }

    /*
     * Split the gps data string and return a string array.
     * Example of GGA string: 123519,4807.038,N,01131.324,E,1,08,0.9,545.4,M,46.9,M, , *42
    */
    private String[] splitString(String s) throws Exception{
        int i=0;
        int pos=0;
        int nextPos=0;

        // check how big the array is.
        while(pos>-1){
            pos = s.indexOf(",", pos);
            if(pos<0){
                continue;
            }
            pos++;
            i++;
        }
        
        if(i>25){
            throw new Exception("to big:" + i);
        }

        i=0;
        pos=0;
        
        // Start splitting the string, search for each ','
        while(pos>-1){
            pos = s.indexOf(",", pos);
            if(pos<0){
                continue;
            }

            nextPos = s.indexOf(",", pos+1);
            if(nextPos<0){
                nextPos = s.length();
            }
            
            result[i] = s.substring(pos+1, nextPos);
            i++;
            if(pos>-1){
                pos++;
            }
        }
        
        return result;
    }    
    
}