Android web service access using Async Task

In Android we can use Async Tasks to perform background activities without interrupting main gui thread. So it is ideal for the tasks like web service accessing in Android. In this post I'm going to demonstrate a very simple application which uses Async Task to access soap based web service. Here I access .NET web service Currency Converter provided by http://www.webservicex.net/. 

To create this application you need to have ksoap2 libaray. (You can download latest version of ksoap2 from here : http://code.google.com/p/ksoap2-android/wiki/HowToUse?tm=2 click the url under "with a direct download url of ").

To import ksoap2 to the java build path follow steps mentioned here.  

Here is the quick demo of the application.

Code for the main activity:

In line 68 I have set "envelope.dotNet = true;" because I'm accessing .NET web service. You can comment that line if you are accessing other web service.

package com.soap.client;

import org.ksoap2.SoapEnvelope;
import org.ksoap2.serialization.PropertyInfo;
import org.ksoap2.serialization.SoapObject;
import org.ksoap2.serialization.SoapPrimitive;
import org.ksoap2.serialization.SoapSerializationEnvelope;
import org.ksoap2.transport.HttpTransportSE;
import android.os.AsyncTask;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity {
 private TextView textView;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  textView = (TextView) findViewById(R.id.textView1);
  this.accessWebService(textView);
 }

 @Override
 public boolean onCreateOptionsMenu(Menu menu) {
  // Inflate the menu; this adds items to the action bar if it is present.
  getMenuInflater().inflate(R.menu.main, menu);
  return true;
 }
 
 //starting asynchronus task
 private class SoapAccessTask extends AsyncTask<String, Void, String> {
     
     @Override 
     protected void onPreExecute() {
          //if you want, start progress dialog here
     }
         
     @Override
     protected String doInBackground(String... urls) {
         String webResponse = "";
        try{
          final String NAMESPACE = "http://www.webserviceX.NET/";
          final String URL = "http://www.webservicex.net/CurrencyConvertor.asmx";
          final String SOAP_ACTION = "http://www.webserviceX.NET/ConversionRate";
          final String METHOD_NAME = "ConversionRate";
          
          SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME); 
          PropertyInfo fromProp =new PropertyInfo();
          fromProp.setName("FromCurrency");
          //gets the first element from urls array
          fromProp.setValue(urls[0]);
          fromProp.setType(String.class);
          request.addProperty(fromProp);
            
          PropertyInfo toProp =new PropertyInfo();
          toProp.setName("ToCurrency");
          //second element of the urls array
          toProp.setValue(urls[1]);
          toProp.setType(String.class);
          request.addProperty(toProp);
           
          SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
          envelope.dotNet = true;
          envelope.setOutputSoapObject(request);
          HttpTransportSE androidHttpTransport = new HttpTransportSE(URL);
          
          androidHttpTransport.call(SOAP_ACTION, envelope);
          SoapPrimitive response = (SoapPrimitive)envelope.getResponse();
          webResponse = response.toString();
       }
       catch(Exception e){
          Toast.makeText(getApplicationContext(),"Cannot access the web service"+e.toString(), Toast.LENGTH_LONG).show(); 
        }
         return webResponse;
    }
  
    @Override
    protected void onPostExecute(String result) {
            //if you started progress dialog dismiss it here
            textView.setText(result);
            Toast.makeText(getApplicationContext(),"Completed...", Toast.LENGTH_LONG).show();
         }
     }
 
   public void accessWebService(View view) {
   SoapAccessTask task = new SoapAccessTask();
      //passes values for the urls string array 
      task.execute(new String[] { "USD","LKR"});
     }  
}

Code for the layout

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="89dp"
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>

You have to add INTERNET permission to AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.soap.client"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-sdk
        android:minSdkVersion="17"
        android:targetSdkVersion="17" />
    <uses-permission android:name="android.permission.INTERNET"/>
    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.soap.client.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
</manifest>

Download Android (4.2.2) project here.
To find more details about Async Task follow the links below
http://developer.android.com/reference/android/os/AsyncTask.html
http://www.vogella.com/articles/AndroidBackgroundProcessing/article.html

If you are getting "Unfortunately stopped" error this post may helpful.

If you want to use handlers to access web services refer below tutorial.
http://codeoncloud.blogspot.com/2013/06/android-java-soap-web-service-access.html

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