title: caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void ... on a null object reference
body: <p>I browse on some question here in stack overflow but it didn't solve my problem. </p>
  
  <p>here's my code. </p>
  
  <pre><code>   public class MenuListActivity extends ListActivity {
  String MenuNames[] = {"Consultation", "Medicine", "Diseases", "Doctor"};
  protected void onCreateView(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_menu_list);
      ArrayAdapter&lt;String&gt; adapter = new ArrayAdapter&lt;String&gt;(this, android.R.layout.simple_list_item_1, MenuNames);
      final ListView lv = (ListView) findViewById(R.id.listView1);
  
      lv.setAdapter(adapter);
  
      lv.setOnItemClickListener(new OnItemClickListener() {
          public void onItemClick(AdapterView&lt;?&gt; parent, View v,
                  int position, long id) {
  
              if(position == 1) {
                  //code specific to first list item    
                  Intent myIntent = new Intent(v.getContext(), ConsultationActivity.class);
                  startActivity(myIntent);
              }
  
  
          }
  
      }
       );
  
  }
  </code></pre>
  
  <p>Logcat. </p>
  
  <pre><code>    10-12 10:53:37.572: E/AndroidRuntime(10605): FATAL EXCEPTION: main
      10-12 10:53:37.572: E/AndroidRuntime(10605): Process: com.capstone.medicinehealthguide, PID:     10605
      10-12 10:53:37.572: E/AndroidRuntime(10605): java.lang.RuntimeException: Unable to start activity      ComponentInfo{com.capstone.medicinehealthguide/com.capstone.medicinehealthguide.MenuListActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2255)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2317)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.ActivityThread.access$800(ActivityThread.java:143)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1258)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.os.Handler.dispatchMessage(Handler.java:102)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.os.Looper.loop(Looper.java:135)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.ActivityThread.main(ActivityThread.java:5070)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at java.lang.reflect.Method.invoke(Native Method)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at java.lang.reflect.Method.invoke(Method.java:372)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:836)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:631)
      10-12 10:53:37.572: E/AndroidRuntime(10605): Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at com.capstone.medicinehealthguide.MenuListActivity.onCreate(MenuListActivity.java:24)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.Activity.performCreate(Activity.java:5720)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1102)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2208)
      10-12 10:53:37.572: E/AndroidRuntime(10605):    ... 10 more
  </code></pre>
  
  <p>XML file</p>
  
  <pre><code>    &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.capstone.medicinehealthguide.MenuListActivity" &gt;
  
  &lt;ListView
      android:id="@+id/listView1"
      android:layout_width="match_parent"
      android:layout_height="wrap_content" &gt;
  
  &lt;/ListView&gt;
  </code></pre>
  
  <p></p>
  
  <p>I'm trying to make an app that has a listview and when you click on it, another activities will be open</p>