Calling a web service from android - NullPointerException

Question

I am trying to use the code from here http://www.ibm.com/developerworks/webservices/library/ws-android/index.html?ca=dat- to call a web service. I keep getting the exception thrown at the following line of my code….

androidHttpTransport.call(SOAP_ACTION, envelope);

The class I've written looks as follows;

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.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends Activity {

    private EditText editext1;
    private EditText editext2;
    private EditText editext3;
    private EditText editext4;
    private Button btn1;

    private static final String NAMESPACE = "http://service.hotornot.com/";
    private static String URL = "http://hotornot-hnwebservice.rhcloud.com/TomcatHotOrNot/messages?wsdl";
    private static final String METHOD_NAME = "addMessage";
    private static final String SOAP_ACTION = "http://service.hotornot.com/addMessage";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        editext1 = (EditText) findViewById(R.id.editText1);
        editext2 = (EditText) findViewById(R.id.editText2);
        editext3 = (EditText) findViewById(R.id.editText3);
        editext4 = (EditText) findViewById(R.id.editText4);
        btn1 = (Button) findViewById(R.id.button1);

        btn1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {

                SoapObject request = new SoapObject(NAMESPACE, METHOD_NAME);

                PropertyInfo propInfo = new PropertyInfo();
                propInfo.name = "arg0";
                propInfo.type = PropertyInfo.STRING_CLASS;
                request.addProperty(propInfo, editext1.getText().toString());

                PropertyInfo propInfo1 = new PropertyInfo();
                propInfo.name = "arg1";
                propInfo.type = PropertyInfo.STRING_CLASS;
                request.addProperty(propInfo1, editext2.getText().toString());

                PropertyInfo propInf2 = new PropertyInfo();
                propInfo.name = "arg2";
                propInfo.type = PropertyInfo.STRING_CLASS;
                request.addProperty(propInf2, editext3.getText().toString());

                PropertyInfo propInfo3 = new PropertyInfo();
                propInfo.name = "arg3";
                propInfo.type = PropertyInfo.STRING_CLASS;
                request.addProperty(propInfo3, editext4.getText().toString());

                SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(
                        SoapEnvelope.VER11);

                envelope.setOutputSoapObject(request);
                HttpTransportSE androidHttpTransport = new HttpTransportSE(URL);

                try {
                    androidHttpTransport.call(SOAP_ACTION, envelope);

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

                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        return true;
    }

}

Interestingly - if i debug the code and check the output of the SoapObject it looks as follows which doesn't seem correct - why is the key null? I assume this is what is causing the null pointer exception

addMessage{arg3=this; null=is; null=a; null=test; }

Exception:

12-31 13:23:47.514: W/System.err(770): java.lang.NullPointerException
    12-31 13:23:47.524: W/System.err(770):  at java.io.Writer.write(Writer.java:141)
    12-31 13:23:47.524: W/System.err(770):  at org.kxml2.io.KXmlSerializer.startTag(KXmlSerializer.java:412)
    12-31 13:23:47.524: W/System.err(770):  at org.ksoap2.serialization.SoapSerializationEnvelope.writeObjectBody(SoapSerializationEnvelope.java:581)
    12-31 13:23:47.534: W/System.err(770):  at org.ksoap2.serialization.SoapSerializationEnvelope.writeObjectBody(SoapSerializationEnvelope.java:566)
    12-31 13:23:47.534: W/System.err(770):  at org.ksoap2.serialization.SoapSerializationEnvelope.writeElement(SoapSerializationEnvelope.java:623)
    12-31 13:23:47.544: W/System.err(770):  at org.ksoap2.serialization.SoapSerializationEnvelope.writeBody(SoapSerializationEnvelope.java:547)
    12-31 13:23:47.544: W/System.err(770):  at org.ksoap2.SoapEnvelope.write(SoapEnvelope.java:192)
    12-31 13:23:47.554: W/System.err(770):  at org.ksoap2.transport.Transport.createRequestData(Transport.java:74)
    12-31 13:23:47.554: W/System.err(770):  at org.ksoap2.transport.HttpTransportSE.call(HttpTransportSE.java:58)
    12-31 13:23:47.564: W/System.err(770):  at com.example.hotornot.MainActivity$1.onClick(MainActivity.java:74)
    12-31 13:23:47.564: W/System.err(770):  at android.view.View.performClick(View.java:4204)
    12-31 13:23:47.564: W/System.err(770):  at android.view.View$PerformClick.run(View.java:17355)
    12-31 13:23:47.574: W/System.err(770):  at android.os.Handler.handleCallback(Handler.java:725)
    12-31 13:23:47.574: W/System.err(770):  at android.os.Handler.dispatchMessage(Handler.java:92)
    12-31 13:23:47.584: W/System.err(770):  at android.os.Looper.loop(Looper.java:137)
    12-31 13:23:47.584: W/System.err(770):  at android.app.ActivityThread.main(ActivityThread.java:5041)
    12-31 13:23:47.594: W/System.err(770):  at java.lang.reflect.Method.invokeNative(Native Method)
    12-31 13:23:47.594: W/System.err(770):  at java.lang.reflect.Method.invoke(Method.java:511)
    12-31 13:23:47.604: W/System.err(770):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
    12-31 13:23:47.604: W/System.err(770):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
    12-31 13:23:47.604: W/System.err(770):  at dalvik.system.NativeStart.main(Native Method)

Answer 1

This solves your problem:

            PropertyInfo propInfo = new PropertyInfo();
            propInfo.name = "arg0";
            propInfo.type = PropertyInfo.STRING_CLASS;
            request.addProperty(propInfo, editext1.getText().toString());

            PropertyInfo propInfo1 = new PropertyInfo();
            propInfo1.name = "arg1";
            propInfo1.type = PropertyInfo.STRING_CLASS;
            request.addProperty(propInfo1, editext2.getText().toString());

            PropertyInfo propInf2 = new PropertyInfo();
            propInf2.name = "arg2";
            propInf2.type = PropertyInfo.STRING_CLASS;
            request.addProperty(propInf2, editext3.getText().toString());

            PropertyInfo propInfo3 = new PropertyInfo();
            propInfo3.name = "arg3";
            propInfo3.type = PropertyInfo.STRING_CLASS;
            request.addProperty(propInfo3, editext4.getText().toString());

Explanation: the assignments of properties "name" and "type" were done on the wrong variable (always the first one propInfo, but should be propInfo1, ...).