title: To Do List Example
body: <p>I am new to Android App Development and have a small problem.</p>
  
  <p>I have tried to follow an example to create a to do list app. However it doesn't work even though I have copied it exactly.</p>
  
  <p>It shows no errors when I run it however, a blank screen appears and after a few seconds it closes and says "Unfortunately, ToDoList has stopped."</p>
  
  <p>Does anyone know what this problem might be?</p>
  
  <p><strong>Code</strong></p>
  
  <pre><code> package com.paad.todolist;
  
      import java.util.ArrayList;
  
      import android.app.Activity;
      import android.os.Bundle;
      import android.view.KeyEvent;
      import android.view.Menu;
      import android.view.View;
      import android.widget.ArrayAdapter;
      import android.widget.EditText;
      import android.widget.ListView;
  
      public class MainActivity extends Activity {
  
          @Override
          protected void onCreate(Bundle savedInstanceState) {
              super.onCreate(savedInstanceState);
  
              setContentView(R.layout.activity_main);
  
              ListView myListView = (ListView)findViewById(R.id.ListView);
              final EditText myEditText = (EditText) findViewById(R.id.EditText);
  
              final ArrayList&lt;String&gt; todoItems = new ArrayList&lt;String&gt;();
              final ArrayAdapter&lt;String&gt; aa;
  
              aa = new ArrayAdapter&lt;String&gt; (this,android.R.layout.simple_list_item_1,todoItems);
  
              myListView.setAdapter(aa);
  
  
          myEditText.setOnKeyListener(new View.OnKeyListener()   {
              public boolean onKey(View v, int keyCode, KeyEvent event)   {
                  if (event.getAction() == KeyEvent.ACTION_DOWN)
                      if ((keyCode == KeyEvent.KEYCODE_DPAD_CENTER)    ||
                          (keyCode == KeyEvent.KEYCODE_ENTER))   {
                          todoItems.add(0, myEditText.getText().toString());
                          aa.notifyDataSetChanged();
                          myEditText.setText("");
                          return true;
                      }
                  return false;
              }
          });
      }
  
          @Override
          public boolean onCreateOptionsMenu(Menu menu) {
              // Inflate the menu; this adds items to the action bar if it is present.
              getMenuInflater().inflate(R.menu.activity_main, menu);
              return true;
          }
  
      }
  </code></pre>
  
  <p><strong>Layout XML File</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:orientation="vertical" &gt;
  
      &lt;EditText 
          android:id="@+id/EditText"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
          android:hint="@string/addItemHint"
          android:contentDescription="@string/addItemContentDescription"
      /&gt;
  
      &lt;ListView
          android:id="@+id/ListView"
          android:layout_width="match_parent"
          android:layout_height="wrap_content"
      /&gt;        
  
  &lt;/LinearLayout&gt;
  </code></pre>
  
  <p>Log:</p>
  
  <pre><code>02-10 20:03:53.850: D/AndroidRuntime(24220): Shutting down VM
  02-10 20:03:53.850: W/dalvikvm(24220): threadid=1: thread exiting with uncaught exception (group=0x40f0a2a0)
  02-10 20:03:53.850: E/AndroidRuntime(24220): FATAL EXCEPTION: main
  02-10 20:03:53.850: E/AndroidRuntime(24220): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.paad.todolist/com.paad.todolist.MainActivity}: java.lang.NullPointerException
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2100)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2125)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.ActivityThread.access$600(ActivityThread.java:140)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1227)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.os.Handler.dispatchMessage(Handler.java:99)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.os.Looper.loop(Looper.java:137)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.ActivityThread.main(ActivityThread.java:4898)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at java.lang.reflect.Method.invokeNative(Native Method)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at java.lang.reflect.Method.invoke(Method.java:511)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at dalvik.system.NativeStart.main(Native Method)
  02-10 20:03:53.850: E/AndroidRuntime(24220): Caused by: java.lang.NullPointerException
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at com.paad.todolist.MainActivity.onCreate(MainActivity.java:30)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.Activity.performCreate(Activity.java:5206)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1083)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2064)
  02-10 20:03:53.850: E/AndroidRuntime(24220):    ... 11 more
  </code></pre>