我没有从andriod调用我的Web服务抛出异常networkonmainthreadexception

 package com.example.test;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.*;

import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;

import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.PropertyInfo;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.serialization.SoapPrimitive;
import org.ksoap2.transport.AndroidHttpTransport;
import org.ksoap2.transport.HttpTransportSE;


public class MainActivity extends Activity {

	 /** Called when the activity is first created. */
    
    private static String SOAP_ACTION = "http://tempuri.org/HelloWorld";
    private static String NAMESPACE = "http://tempuri.org/";
    private static String METHOD_NAME = "HelloWorld";
    private static String URL = "http://117.227.58.74/vehicle//WebService.asmx";
    String weight = "77";
    String fromUnit = "78";

	TextView tv;
	
	
    @Override
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    //tv =(TextView)findViewById(R.id.textView1);
        
        
    
    SoapObject Request = new SoapObject(NAMESPACE, METHOD_NAME);
    
    PropertyInfo weightProp =new PropertyInfo();
    weightProp.setName("lat");
    weightProp.setValue(weight);
    weightProp.setType(double.class);
    Request.addProperty(weightProp);
     
    PropertyInfo fromProp =new PropertyInfo();
    fromProp.setName("log");
    fromProp.setValue(fromUnit);
    fromProp.setType(double.class);
    Request.addProperty(fromProp);
   
    SoapSerializationEnvelope soapEnvelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);    
    soapEnvelope.dotNet = true;
    soapEnvelope.setOutputSoapObject(Request);
    Toast.makeText(getBaseContext(),"1",Toast.LENGTH_LONG).show();
    HttpTransportSE aht = new HttpTransportSE(URL);
    try 
    {
    	Toast.makeText(getBaseContext(),"2",Toast.LENGTH_LONG).show();
    	aht.call(SOAP_ACTION, soapEnvelope);
    	Toast.makeText(getBaseContext(),"3",Toast.LENGTH_LONG).show();
    	SoapPrimitive resultString = (SoapPrimitive)soapEnvelope.getResponse();
    	Toast.makeText(getBaseContext(),"4",Toast.LENGTH_LONG).show();
    	 //Log.i("myApp", response.toString());
    	//tv.setText("Status:" + resultString);
    	
    	
    } catch (Exception e)
    	
    {
    
    	e.printStackTrace(); 
    
   	   }

    }
}