Android [GPS GetSpeed] รบกวนขอลิงค์ข้อมูลหรือตัวอย่างการ คำนวณความเร็วจาก GPS หน่อยครับ

package gd.Speedometer; 

import android.app.Activity; 
import android.os.Bundle; 
import android.widget.TextView; 
import android.content.Context; 
import android.location.Location; 
import android.location.LocationListener; 
import android.location.LocationManager; 
import android.util.Log; 

public class Speedometer extends Activity { 

        private TextView tv; 
        private LocationManager lm; 
        private LocationListener ll; 
        double mySpeed, maxSpeed; 
        private final String Speed = null; 
    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
            Log.i(Speed, "working1 "); 
            super.onCreate(savedInstanceState); 
            tv = new TextView(this); 
            setContentView(tv); 

            maxSpeed = mySpeed = 0; 
            Log.i(Speed, "working1 "); 
            lm = (LocationManager) getSystemService 
(Context.LOCATION_SERVICE); 
            ll = new SpeedoActionListener(); 
            lm.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, 
ll); 
    } 

    private class SpeedoActionListener implements LocationListener 
    { 



                @Override 
                public void onLocationChanged(Location location) { 
                        Log.i(Speed, "working2 "); 
                        if(location!=null) { 
                                if(location.hasSpeed()){ 

                                        mySpeed = location.getSpeed(); 

                                        tv.setText("\nCurrent speed: " + mySpeed + " km/h, Max speed: " + 
maxSpeed + " km/h"); 
                                } 
                        } 
                        Log.i(Speed, "working3 "); 
                } 

                @Override 
                public void onProviderDisabled(String provider) { 
                        // TODO Auto-generated method stub 

                } 

                @Override 
                public void onProviderEnabled(String provider) { 
                        // TODO Auto-generated method stub 

                } 

                @Override 
                public void onStatusChanged(String provider, int status, Bundle 
extras) { 
                        // TODO Auto-generated method stub 

                } 
    } 
}