Android java.lang.IllegalStateException: Could not execute method of the activity

Question

Hello I'm new to learning android and I'm trying to make a semi-useful app (to myself) while learning Android, I'm basically at the minute taking useful bits of Java code (ping X, Port Scan) and adding them to my app, I cannot figure out why this error is occurring, I do believe it is to do with Line 77 of the code but I want to learn why it is isn't working so I can better help myself next time. Sorry for the wordy question, I don't know when to shut up.

01-25 20:42:42.139: E/AndroidRuntime(1307): FATAL EXCEPTION: main
01-25 20:42:42.139: E/AndroidRuntime(1307): java.lang.IllegalStateException: Could not execute method of the activity
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.view.View$1.onClick(View.java:3597)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.view.View.performClick(View.java:4202)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.view.View$PerformClick.run(View.java:17340)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.os.Handler.handleCallback(Handler.java:725)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.os.Looper.loop(Looper.java:137)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.app.ActivityThread.main(ActivityThread.java:5191)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at dalvik.system.NativeStart.main(Native Method)
01-25 20:42:42.139: E/AndroidRuntime(1307): Caused by: java.lang.reflect.InvocationTargetException
01-25 20:42:42.139: E/AndroidRuntime(1307):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:42:42.139: E/AndroidRuntime(1307):     at android.view.View$1.onClick(View.java:3592)
01-25 20:42:42.139: E/AndroidRuntime(1307):     ... 11 more
01-25 20:42:42.139: E/AndroidRuntime(1307): Caused by: java.lang.NullPointerException
01-25 20:42:42.139: E/AndroidRuntime(1307):     at com.seven.up.MainActivity.OnClickPort(MainActivity.java:77)
01-25 20:42:42.139: E/AndroidRuntime(1307):     ... 14 more
01-25 20:44:42.549: E/MPL-storeload(511): calData from inv_save_mpl_states, size=2
01-25 20:45:39.759: E/InputDispatcher(511): channel '41b55368 com.seven.up/com.seven.up.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
01-25 20:45:50.279: E/AndroidRuntime(1625): FATAL EXCEPTION: main
01-25 20:45:50.279: E/AndroidRuntime(1625): java.lang.IllegalStateException: Could not execute method of the activity
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.view.View$1.onClick(View.java:3597)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.view.View.performClick(View.java:4202)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.view.View$PerformClick.run(View.java:17340)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.os.Handler.handleCallback(Handler.java:725)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.os.Looper.loop(Looper.java:137)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.app.ActivityThread.main(ActivityThread.java:5191)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at dalvik.system.NativeStart.main(Native Method)
01-25 20:45:50.279: E/AndroidRuntime(1625): Caused by: java.lang.reflect.InvocationTargetException
01-25 20:45:50.279: E/AndroidRuntime(1625):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:45:50.279: E/AndroidRuntime(1625):     at android.view.View$1.onClick(View.java:3592)
01-25 20:45:50.279: E/AndroidRuntime(1625):     ... 11 more
01-25 20:45:50.279: E/AndroidRuntime(1625): Caused by: java.lang.NullPointerException
01-25 20:45:50.279: E/AndroidRuntime(1625):     at com.seven.up.MainActivity.OnClickPort(MainActivity.java:78)
01-25 20:45:50.279: E/AndroidRuntime(1625):     ... 14 more
01-25 20:46:32.409: E/InputDispatcher(511): channel '416e8e78 com.seven.up/com.seven.up.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
01-25 20:46:35.449: E/AndroidRuntime(1830): FATAL EXCEPTION: main
01-25 20:46:35.449: E/AndroidRuntime(1830): java.lang.IllegalStateException: Could not execute method of the activity
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.view.View$1.onClick(View.java:3597)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.view.View.performClick(View.java:4202)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.view.View$PerformClick.run(View.java:17340)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.os.Handler.handleCallback(Handler.java:725)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.os.Looper.loop(Looper.java:137)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.app.ActivityThread.main(ActivityThread.java:5191)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at dalvik.system.NativeStart.main(Native Method)
01-25 20:46:35.449: E/AndroidRuntime(1830): Caused by: java.lang.reflect.InvocationTargetException
01-25 20:46:35.449: E/AndroidRuntime(1830):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:46:35.449: E/AndroidRuntime(1830):     at android.view.View$1.onClick(View.java:3592)
01-25 20:46:35.449: E/AndroidRuntime(1830):     ... 11 more
01-25 20:46:35.449: E/AndroidRuntime(1830): Caused by: java.lang.NullPointerException
01-25 20:46:35.449: E/AndroidRuntime(1830):     at com.seven.up.MainActivity.OnClickPort(MainActivity.java:77)
01-25 20:46:35.449: E/AndroidRuntime(1830):     ... 14 more
01-25 20:47:40.119: E/AndroidRuntime(2009): FATAL EXCEPTION: main
01-25 20:47:40.119: E/AndroidRuntime(2009): java.lang.IllegalStateException: Could not execute method of the activity
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.view.View$1.onClick(View.java:3597)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.view.View.performClick(View.java:4202)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.view.View$PerformClick.run(View.java:17340)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.os.Handler.handleCallback(Handler.java:725)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.os.Looper.loop(Looper.java:137)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.app.ActivityThread.main(ActivityThread.java:5191)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at dalvik.system.NativeStart.main(Native Method)
01-25 20:47:40.119: E/AndroidRuntime(2009): Caused by: java.lang.reflect.InvocationTargetException
01-25 20:47:40.119: E/AndroidRuntime(2009):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:47:40.119: E/AndroidRuntime(2009):     at android.view.View$1.onClick(View.java:3592)
01-25 20:47:40.119: E/AndroidRuntime(2009):     ... 11 more
01-25 20:47:40.119: E/AndroidRuntime(2009): Caused by: java.lang.NullPointerException
01-25 20:47:40.119: E/AndroidRuntime(2009):     at com.seven.up.MainActivity.OnClickPort(MainActivity.java:77)
01-25 20:47:40.119: E/AndroidRuntime(2009):     ... 14 more
01-25 20:49:29.979: E/InputDispatcher(511): channel '414e7770 com.seven.up/com.seven.up.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
01-25 20:49:30.149: E/jdwp(2216): Failed sending reply to debugger: Broken pipe
01-25 20:49:41.599: E/MPL-storeload(511): calData from inv_save_mpl_states, size=2
01-25 20:50:12.539: E/InputDispatcher(511): channel '41c0a160 com.seven.up/com.seven.up.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
01-25 20:50:13.629: E/InputManager-JNI(511): An exception was thrown by callback 'interceptKeyBeforeQueueing'.
01-25 20:50:13.629: E/InputManager-JNI(511): java.lang.NullPointerException
01-25 20:50:13.629: E/InputManager-JNI(511):    at com.android.internal.policy.impl.PhoneWindowManager.interceptKeyBeforeQueueing(PhoneWindowManager.java:3948)
01-25 20:50:13.629: E/InputManager-JNI(511):    at com.android.server.wm.InputMonitor.interceptKeyBeforeQueueing(InputMonitor.java:337)
01-25 20:50:13.629: E/InputManager-JNI(511):    at com.android.server.input.InputManagerService.interceptKeyBeforeQueueing(InputManagerService.java:1346)
01-25 20:50:13.629: E/InputManager-JNI(511):    at dalvik.system.NativeStart.run(Native Method)
01-25 20:50:13.899: E/InputManager-JNI(511): An exception was thrown by callback 'interceptKeyBeforeQueueing'.
01-25 20:50:13.899: E/InputManager-JNI(511): java.lang.NullPointerException
01-25 20:50:13.899: E/InputManager-JNI(511):    at com.android.internal.policy.impl.PhoneWindowManager.interceptKeyBeforeQueueing(PhoneWindowManager.java:3948)
01-25 20:50:13.899: E/InputManager-JNI(511):    at com.android.server.wm.InputMonitor.interceptKeyBeforeQueueing(InputMonitor.java:337)
01-25 20:50:13.899: E/InputManager-JNI(511):    at com.android.server.input.InputManagerService.interceptKeyBeforeQueueing(InputManagerService.java:1346)
01-25 20:50:13.899: E/InputManager-JNI(511):    at dalvik.system.NativeStart.run(Native Method)
01-25 20:50:19.759: E/InputDispatcher(511): channel '41419b38 com.seven.up/com.seven.up.MainActivity (server)' ~ Channel is unrecoverably broken and will be disposed!
01-25 20:51:49.459: E/WeatherXmlParser(2522): Couldn't parse Yahoo weather XML
01-25 20:51:49.459: E/WeatherXmlParser(2522): java.lang.NumberFormatException: Invalid float: ""
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.lang.StringToReal.invalidReal(StringToReal.java:63)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.lang.StringToReal.parseFloat(StringToReal.java:289)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.lang.Float.parseFloat(Float.java:300)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at com.cyanogenmod.lockclock.weather.WeatherXmlParser.getFloatForAttribute(WeatherXmlParser.java:86)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at com.cyanogenmod.lockclock.weather.WeatherXmlParser.parseWeatherResponse(WeatherXmlParser.java:108)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at com.cyanogenmod.lockclock.weather.WeatherUpdateService$WeatherUpdateTask.doInBackground(WeatherUpdateService.java:210)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at com.cyanogenmod.lockclock.weather.WeatherUpdateService$WeatherUpdateTask.doInBackground(WeatherUpdateService.java:126)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at android.os.AsyncTask$2.call(AsyncTask.java:287)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.util.concurrent.FutureTask.run(FutureTask.java:234)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1080)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:573)
01-25 20:51:49.459: E/WeatherXmlParser(2522):   at java.lang.Thread.run(Thread.java:856)
01-25 20:52:24.619: E/MPL-storeload(511): calData from inv_save_mpl_states, size=2
01-25 20:57:07.229: E/AndroidRuntime(2410): FATAL EXCEPTION: main
01-25 20:57:07.229: E/AndroidRuntime(2410): java.lang.IllegalStateException: Could not execute method of the activity
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.view.View$1.onClick(View.java:3597)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.view.View.performClick(View.java:4202)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.view.View$PerformClick.run(View.java:17340)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.os.Handler.handleCallback(Handler.java:725)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.os.Looper.loop(Looper.java:137)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.app.ActivityThread.main(ActivityThread.java:5191)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at dalvik.system.NativeStart.main(Native Method)
01-25 20:57:07.229: E/AndroidRuntime(2410): Caused by: java.lang.reflect.InvocationTargetException
01-25 20:57:07.229: E/AndroidRuntime(2410):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:57:07.229: E/AndroidRuntime(2410):     at android.view.View$1.onClick(View.java:3592)
01-25 20:57:07.229: E/AndroidRuntime(2410):     ... 11 more
01-25 20:57:07.229: E/AndroidRuntime(2410): Caused by: java.lang.NullPointerException
01-25 20:57:07.229: E/AndroidRuntime(2410):     at com.seven.up.MainActivity.OnClickPort(MainActivity.java:77)
01-25 20:57:07.229: E/AndroidRuntime(2410):     ... 14 more
01-25 20:59:12.549: E/AndroidRuntime(3168): FATAL EXCEPTION: main
01-25 20:59:12.549: E/AndroidRuntime(3168): java.lang.IllegalStateException: Could not execute method of the activity
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.view.View$1.onClick(View.java:3597)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.view.View.performClick(View.java:4202)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.view.View$PerformClick.run(View.java:17340)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.os.Handler.handleCallback(Handler.java:725)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.os.Handler.dispatchMessage(Handler.java:92)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.os.Looper.loop(Looper.java:137)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.app.ActivityThread.main(ActivityThread.java:5191)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at dalvik.system.NativeStart.main(Native Method)
01-25 20:59:12.549: E/AndroidRuntime(3168): Caused by: java.lang.reflect.InvocationTargetException
01-25 20:59:12.549: E/AndroidRuntime(3168):     at java.lang.reflect.Method.invokeNative(Native Method)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at java.lang.reflect.Method.invoke(Method.java:511)
01-25 20:59:12.549: E/AndroidRuntime(3168):     at android.view.View$1.onClick(View.java:3592)
01-25 20:59:12.549: E/AndroidRuntime(3168):     ... 11 more
01-25 20:59:12.549: E/AndroidRuntime(3168): Caused by: java.lang.NullPointerException
01-25 20:59:12.549: E/AndroidRuntime(3168):     at com.seven.up.MainActivity.OnClickPort(MainActivity.java:76)
01-25 20:59:12.549: E/AndroidRuntime(3168):     ... 14 more
01-25 21:01:13.939: E/MPL-storeload(511): calData from inv_save_mpl_states, size=2

package com.seven.up;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.*;

import android.app.Activity;
import android.os.Bundle;
import android.text.Editable;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {
    EditText ip_address_field;
    TextView scan_out;
    TextView port_results;
    EditText startPort;
    EditText stopPort;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        ip_address_field = (EditText) findViewById(R.id.ip_address_field);
        ip_address_field.getText();
        scan_out = (TextView) findViewById(R.id.scan_out);

        Button scan_button = (Button) findViewById(R.id.scan_button);
        scan_button.setOnClickListener(this);
    }

    public void onClick(View v) {
        Editable host = ip_address_field.getText();

        switch (v.getId()) {

        case R.id.scan_button:
            try {
                String pingCmd = "ping -c 5 " + host;
                String pingResult = "";
                Runtime r = Runtime.getRuntime();
                Process p = r.exec(pingCmd);
                BufferedReader in = new BufferedReader(new InputStreamReader(
                        p.getInputStream()));
                String inputLine;
                while ((inputLine = in.readLine()) != null) {
                    System.out.println(inputLine);
                    scan_out.setText(inputLine + "\n" + "\n");
                    pingResult += inputLine;
                    scan_out.setText("/n" + pingResult);
                }
                in.close();
            }// try
            catch (IOException e) {
                System.out.println(e);
            }
            break;

        default:
            break;
        }

    }

    public void OnClickPort(View v) {
        switch (v.getId()) {
        case R.id.button1:

        int startPortRange = Integer.parseInt(startPort.getText().toString());
        int stopPortRange = Integer.parseInt(stopPort.getText().toString());

        for (int i = startPortRange; i <= stopPortRange; i++) {
            try {
                Socket ServerSok = new Socket("192.168.0.1", i);

                Toast.makeText(getApplicationContext(), "Port in use: " + i, Toast.LENGTH_LONG).show();

                ServerSok.close();
            } catch (Exception e) {
            }
            System.out.println("Port not in use: " + i);
        } 
        }
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.activity_main, menu);
        return super.onCreateOptionsMenu(menu);
    }
}

Answer 1

I had the same issue:

Just initialize/declare you View fields below these lines in the onCreate Fuction:

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

E.g.

protected void onCreate(Bundle savedInstanceState) 
 {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    bart = (ImageView) findViewById(R.id.bartView);
    homer = (ImageView) findViewById(R.id.homerView);
}

Answer 2

Either

• Didn't initialise a variable or
• Initialised a variable and overwrote it when you were declaring them

Often people duplicate the same line in anticipation to change one variable name in each line, to try and make it faster for you, but might forget one line, or miss one word change

EditText stopPort;

That is your problem

Answer 3

Kind of late reply but still, @Pheonix2105, As mentioned by Reimeus,

EditText startPort, stopPort;

just declares the variables. This does not initialize the values for these declared variables. Hence the value of these variables are currently 'null'.

stopPort = (EditText) findViewById (R.id.stop_port_field)

initializes (or in your terms, ties the stopPort to a UI component) the value of stopPort, thereby avoiding the NullPointerException (which in turn causes the IllegalStatementException in your case).

Hope that clarifies your doubt.

Answer 4

This line is throwing anNPE, producing an IllegalStateException in the exception chain:

int stopPortRange = Integer.parseInt(stopPort.getText().toString());

as you don't initialize stopPort (or startPort) in your onCreate method. You should have something like:

stopPort = (EditText) findViewById(R.id.stop_port_field);

The statement

EditText stopPort;

simply declares the variable which is null by default. Only instances that have been instantiated can have their methods invoked.