title: Getting IllegalStateException on button click
body: <p>On clicking a button to migrate to another activity, the app crashes and log shows:</p>
  
  <pre><code>java.lang.IllegalStateException: Could not execute method for android:onClick
  </code></pre>
  
  <p>To debug, I tried to migrate to a blank activity still it shows the same error. Can't understand why!</p>
  
  <p>This is my main activity java file and it shows error in host()'s intent function:</p>
  
  <pre><code>package com.example.unholyalliance.infinitestream;
  
  import android.content.Context;
  import android.content.Intent;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.view.View;
  import android.widget.Toast;
  
  public class MainActivity extends AppCompatActivity {
  
      @Override
      protected void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_main);
      }
  
      public void host(View v)
      {
          Intent i = new Intent(this,Host.class);
          try
          {
              startActivity(i);
          }catch(IllegalStateException e)
          {
              Context context = getApplicationContext();
              CharSequence text = e.getMessage();
              int duration = Toast.LENGTH_SHORT;
  
              Toast toast = Toast.makeText(context, text, duration);
              toast.show();
          }
      }
  
      public void search(View v)
      {
  
      }
  }
  
  
  
  This is my Host.java file:
  
  import android.content.Context;
  
  import android.net.nsd.NsdManager;
  import android.net.nsd.NsdServiceInfo;
  import android.support.v7.app.AppCompatActivity;
  import android.os.Bundle;
  import android.widget.TextView;
  
  import java.io.IOException;
  import java.net.ServerSocket;
  
  public class Host extends AppCompatActivity {
  
      public String mServiceName="Stream";
      ServerSocket mServerSocket=null;
      NsdManager.RegistrationListener mRegistrationListener=null;
      private NsdManager mNsdManager=null;
      int port=9000;
      TextView service_status = (TextView) findViewById(R.id.textView1);
      @Override
      protected void onCreate(Bundle savedInstanceState)
      {
          super.onCreate(savedInstanceState);
          setContentView(R.layout.activity_host);
          mNsdManager = (NsdManager) getSystemService(Context.NSD_SERVICE);
          try {
              initializeServerSocket();
          } catch (IOException e) {
              e.printStackTrace();
          }
      }
  
      public void initializeServerSocket() throws IOException {
          //Initialize a server socket on the next available port.
          mServerSocket = new ServerSocket(0);
  
          // Store the chosen port.
          port =  mServerSocket.getLocalPort();
          registerService(port);
  
      }
  
      public void registerService(int port) {
          // Create the NsdServiceInfo object, and populate it.
          NsdServiceInfo serviceInfo  = new NsdServiceInfo();
  
          // The name is subject to change based on conflicts
          // with other services advertised on the same network.
          serviceInfo.setServiceName("Stream");
          serviceInfo.setServiceType("_http._tcp.");
          serviceInfo.setPort(port);
          mNsdManager.registerService(
                  serviceInfo, NsdManager.PROTOCOL_DNS_SD, mRegistrationListener);
          initializeRegistrationListener();
  
  
      }
  
  
  
      public void initializeRegistrationListener() {
          mRegistrationListener = new NsdManager.RegistrationListener() {
  
              @Override
              public void onServiceRegistered(NsdServiceInfo NsdServiceInfo) {
                  // Save the service name.  Android may have changed it in order to
                  // resolve a conflict, so update the name you initially requested
                  // with the name Android actually used.
                  mServiceName = NsdServiceInfo.getServiceName();
                service_status.setText("Success");
              }
  
              @Override
              public void onRegistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
                  // Registration failed!  Put debugging code here to determine why.
                  service_status.setText("Registration Failed!");
              }
  
              @Override
              public void onServiceUnregistered(NsdServiceInfo arg0) {
                  // Service has been unregistered.  This only happens when you call
                  // NsdManager.unregisterService() and pass in this listener.
                  service_status.setText("Registration not done");
              }
  
              @Override
              public void onUnregistrationFailed(NsdServiceInfo serviceInfo, int errorCode) {
                  // Unregistration failed.  Put debugging code here to determine why.
                  service_status.setText("Unregistration failed");
              }
          };
      }
  }
  </code></pre>
  
  <p>Full Stack Trace:</p>
  
  <pre><code>E/AndroidRuntime: FATAL EXCEPTION: main
   java.lang.IllegalStateException: Could not execute method for android:onClick
       at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
       at android.view.View.performClick(View.java:4278)
       at android.view.View$PerformClick.run(View.java:17429)
       at android.os.Handler.handleCallback(Handler.java:725)
       at android.os.Handler.dispatchMessage(Handler.java:92)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:5099)
       at java.lang.reflect.Method.invokeNative(Native Method)
       at java.lang.reflect.Method.invoke(Method.java:511)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:803)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:570)
       at dalvik.system.NativeStart.main(Native Method)
    Caused by: java.lang.reflect.InvocationTargetException
       at java.lang.reflect.Method.invokeNative(Native Method)
       at java.lang.reflect.Method.invoke(Method.java:511)
       at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
       at android.view.View.performClick(View.java:4278) 
       at android.view.View$PerformClick.run(View.java:17429) 
       at android.os.Handler.handleCallback(Handler.java:725) 
       at android.os.Handler.dispatchMessage(Handler.java:92) 
       at android.os.Looper.loop(Looper.java:137) 
       at android.app.ActivityThread.main(ActivityThread.java:5099) 
       at java.lang.reflect.Method.invokeNative(Native Method) 
       at java.lang.reflect.Method.invoke(Method.java:511) 
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:803) 
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:570) 
       at dalvik.system.NativeStart.main(Native Method) 
    Caused by: android.content.ActivityNotFoundException: Unable to find explicit activity class {com.example.unholyalliance.infinitestream/com.example.unholyalliance.infinitestream.Host}; have you declared this activity in your AndroidManifest.xml?
       at android.app.Instrumentation.checkStartActivityResult(Instrumentation.java:1633)
       at android.app.Instrumentation.execStartActivity(Instrumentation.java:1425)
       at android.app.Activity.startActivityForResult(Activity.java:3370)
       at android.app.Activity.startActivityForResult(Activity.java:3331)
       at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:843)
       at android.app.Activity.startActivity(Activity.java:3566)
       at android.app.Activity.startActivity(Activity.java:3534)
       at com.example.unholyalliance.infinitestream.MainActivity.host(MainActivity.java:23)
       at java.lang.reflect.Method.invokeNative(Native Method) 
       at java.lang.reflect.Method.invoke(Method.java:511) 
       at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
       at android.view.View.performClick(View.java:4278) 
       at android.view.View$PerformClick.run(View.java:17429) 
       at android.os.Handler.handleCallback(Handler.java:725) 
       at android.os.Handler.dispatchMessage(Handler.java:92) 
       at android.os.Looper.loop(Looper.java:137) 
       at android.app.ActivityThread.main(ActivityThread.java:5099) 
       at java.lang.reflect.Method.invokeNative(Native Method) 
       at java.lang.reflect.Method.invoke(Method.java:511) 
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:803) 
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:570) 
       at dalvik.system.NativeStart.main(Native Method) 
  </code></pre>
  
  <p>activity_main.xml file:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;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="com.example.unholyalliance.infinitestream.MainActivity"&gt;
  
      &lt;Button
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Host"
          android:id="@+id/host_button"
          android:layout_alignParentTop="true"
          android:layout_centerHorizontal="true"
          android:layout_marginTop="104dp"
          android:clickable="true"
          android:onClick="host" /&gt;
  
      &lt;Button
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Search"
          android:id="@+id/search_button"
          android:layout_centerVertical="true"
          android:layout_centerHorizontal="true"
          android:onClick="search"
          android:clickable="true" /&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>