Android Webservice example

In this post, I will be discussing how to invoke web service from Android application. When web methods are invoked from inside Android application, the application gets back the data from the server in the form of XML. The response which has been received can be parsed and rendered in the application as needed.

What is SOAP?

SOAP is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks. It relies on Extensible Markup Language (XML) for its message format, and usually relies on other Application Layer protocols, most notably Hypertext Transfer Protocol (HTTP) and Simple Mail Transfer Protocol (SMTP), for message negotiation and transmission.

What are we going to develop?

We are gonna develop a simple application to demonstrate how web service is invoked using SOAP protocol in Android application. Application we develop will just convert celcius to Fahrenhiet.

As this application requires Internet connectivity to hit Web Service hosted in remote server, it would be good if Internet connectivity check is done before trying to hit Web Service.

Layout XML:
Open main.xml present under /res/layout folder and replace the XML with the below one.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="10dp"
        android:gravity="center"
        android:text="Celsius to Farenheit"
        android:textSize="30dp" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:numeric="integer"
        android:singleLine="true" />

    <Button
        android:id="@+id/button1"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:gravity="center"
        android:text="Convert to Farenheit" />

    <TextView
        android:id="@+id/tv_result"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:text="" android:textSize="26dp"/>


</LinearLayout>


Create following objects under WebserviceActivity class:

private final String NAMESPACE = "http://www.w3schools.com/webservices/";
private final String URL = "http://www.w3schools.com/webservices/tempconvert.asmx";
private final String SOAP_ACTION = "http://www.w3schools.com/webservices/CelsiusToFahrenheit";
private final String METHOD_NAME = "CelsiusToFahrenheit";
private String TAG = "PGGURU";
private static String celcius;
private static String fahren;
Button b;
TextView tv;

EditText et;

onCreate():
Add following code snippet in the place of onCreate method.

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    //Celcius Edit Control
    et = (EditText) findViewById(R.id.editText1);
    //Fahrenheit Text control
    tv = (TextView) findViewById(R.id.tv_result);
    //Button to trigger web service invocation
    b = (Button) findViewById(R.id.button1);
    //Button Click Listener
    b.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            //Check if Celcius text control is not empty
            if (et.getText().length() != 0 && et.getText().toString() != "") {
                //Get the text control value
                celcius = et.getText().toString();
                //Create instance for AsyncCallWS
                AsyncCallWS task = new AsyncCallWS();
                //Call execute 
                task.execute();
            //If text control is empty
            } else {
                tv.setText("Please enter Celcius");
            }
        }
    });

}

Class AsyncCallWS:

Create it as inner class inside WebserviceActivity class.
This class will perform the webservice call which will be executed as separate thread. When execute method is called in onCreate method, it calls the following methods in order:
onPreExecute() – Fahrenheit textview control is set with text ‘Calculation…’
doInBackground() – Invoke getFahrenheit()
onProgressUpdate() -Does nothing
onPostExecute() – Set the Fahrenheit value in textview control

private class AsyncCallWS extends AsyncTask<String, Void, Void> {
        @Override
        protected Void doInBackground(String... params) {
            Log.i(TAG, "doInBackground");
            getFahrenheit(celcius);
            return null;
        }

        @Override
        protected void onPostExecute(Void result) {
            Log.i(TAG, "onPostExecute");
            tv.setText(fahren + "° F");
        }

        @Override
        protected void onPreExecute() {
            Log.i(TAG, "onPreExecute");
            tv.setText("Calculating...");
        }

        @Override
        protected void onProgressUpdate(Void... values) {
            Log.i(TAG, "onProgressUpdate");
        }


    }

getFahrenheit()
Create this method inside WebserviceActivity class.
Method which involves web service invocation:

public void getFahrenheit(String celsius) {

    //Create request

    SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);

    //Property which holds input parameters

    PropertyInfo celsiusPI = new PropertyInfo();

    //Set Name

    celsiusPI.setName("Celsius");

    //Set Value

    celsiusPI.setValue(celsius);

    //Set dataType

    celsiusPI.setType(double.class);

    //Add the property to request object

    request.addProperty(celsiusPI);

    //Create envelope

    SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(

            SoapEnvelope.VER11);

    envelope.dotNet = true;

    //Set output SOAP object

    envelope.setOutputSoapObject(request);

    //Create HTTP call object

    HttpTransportSE androidHttpTransport = new HttpTransportSE(URL);

    try {

        //Invole web service

        androidHttpTransport.call(SOAP_ACTION, envelope);

        //Get the response

        SoapPrimitive response = (SoapPrimitive) envelope.getResponse();

        //Assign it to fahren static variable

        fahren = response.toString();

    } catch (Exception e) {

        e.printStackTrace();

    }

}