如何从 Android Studio 项目调用 web 服务

Question

I am new to Android and Java so excuse my lack of knowledge. Taking this time during quarantine and trying to get a response to a web service I wrote in .NET It is a simple service. Pass userid and passwd and it returns the user last name if found or NO if not found. I have a VB 2017 program that is working as expected but trying to also have the same results in an Android environment.

Here are my imports.

import java.io.IOException;
import java.net.SocketException;
import org.ksoap2.SoapEnvelope;
import org.ksoap2.SoapFault;
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 org.xmlpull.v1.XmlPullParserException;

On a button click I have the following.

{
  String userID = "Tom";
  String pwd = "&yhe$43*";

  userid = new PropertyInfo();
  password = new PropertyInfo();

  SoapObject request = new SoapObject("http://tempuri.org/", "WebService1");

  SoapSerializationEnvelope envelope = new SoapSerializationEnvelope(SoapEnvelope.VER11);
  envelope.dotNet = true;
  envelope.setOutputSoapObject(request);
  HttpTransportSE httpTransport = new HttpTransportSE(URL);

  userid.setName("userID");
  userid.setValue(userID);
  userid.setType(String.class);
  password.setName("password");
  password.setValue("Yo");
  password.setType(String.class);

  request.addProperty(userid);
  request.addProperty(password);
  try {
    httpTransport.call(SOAP_ACTION, envelope);
    SoapPrimitive response = (SoapPrimitive) envelope.getResponse();
    String resp = response.toString();
    Toast.makeText(MainActivity.this, (CharSequence) resp, Toast.LENGTH_LONG).show();
  } catch (Exception e) {
    Toast.makeText(MainActivity.this, (CharSequence) e, Toast.LENGTH_LONG).show();
  }
}

Error is happening on this line:

httpTransport.call(SOAP_ACTION, envelope); 

Looks like it is getting a

java.lang.reflect.InvocationTargetException

Is there something obviously wrong here. I could use some guidance.

Here is data Logcat:

java.lang.IllegalStateException: Could not execute method for android:onClick
    at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:402)
    at android.view.View.performClick(View.java:6294)
    at android.view.View$PerformClick.run(View.java:24770)
    at android.os.Handler.handleCallback(Handler.java:790)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6494)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.reflect.InvocationTargetException
    at java.lang.reflect.Method.invoke(Native Method)
    at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:397)
    at android.view.View.performClick(View.java:6294) 
    at android.view.View$PerformClick.run(View.java:24770) 
    at android.os.Handler.handleCallback(Handler.java:790) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6494) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
Caused by: java.lang.ClassCastException: android.os.NetworkOnMainThreadException cannot be cast to java.lang.CharSequence
    at com.example.myapplication.MainActivity.getName(MainActivity.java:71)
    at java.lang.reflect.Method.invoke(Native Method) 
    at androidx.appcompat.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:397) 
    at android.view.View.performClick(View.java:6294) 
    at android.view.View$PerformClick.run(View.java:24770) 
    at android.os.Handler.handleCallback(Handler.java:790) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:164) 
    at android.app.ActivityThread.main(ActivityThread.java:6494) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)

Answer 1

The problem is this line, I would assume:

       Toast.makeText(MainActivity.this, (CharSequence) e, Toast.LENGTH_LONG).show();

You're casting e (of type "Exception") to a CharSequence, which is obviously illegal, since a class can't inherit from both Exception and CharSequence.

Try using "e.getMessage()" instead of "(CharSequence) e". That won't fix the actual cause of the exception but at least you will be able to see what the actual exception is.

Answer 2

android.os.NetworkOnMainThreadException 

From the error log you posted, I can see that you are doing a Network task in the android main thread.

this exception comes when you do Network operation on the main thread. please schedule this task in a background thread.

For your reference, I have included a link that describes how to solve this How to fix 'android.os.NetworkOnMainThreadException'?

And also change this

Toast.makeText(MainActivity.this, (CharSequence) e, Toast.LENGTH_LONG).show();

to

Toast.makeText(MainActivity.this, e.getMessage(), Toast.LENGTH_LONG).show();

finally, make sure you have added Inte.net permission in the manifest file.

Happy coding!!