Getting IllegalStateException on button click
<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>