title: Switching from activity to MapActivity
body: <pre><code>        Button showmapButton = (Button)findViewById(R.id.showmap);
      showmapButton.setOnClickListener(new View.OnClickListener() {
  public void onClick(View v) {
      Intent intent = new Intent(HomePage.this,
        ShowMap.class);
      intent.putExtra("username", value);
      startActivity(intent);
     }
          });
  </code></pre>
  
  <p>In my main menu i have a button 'ShowMap'
  Everytime i click on showmap my map will hit a null pointer exception causing the program to crash.
  'ShowMap' works fi
  ne if i launch straight to that page without having a need to click button to call that activity.</p>
  
  <p>I tried changing all my files to "extends MapActivity" instead of regular activitiy but the program will still crash whenever i click on show map</p>
  
  <hr>
  
  <pre><code>D/AndroidRuntime(  347): Shutting down VM
  W/dalvikvm(  347): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
  E/AndroidRuntime(  347): FATAL EXCEPTION: main
  E/AndroidRuntime(  347): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mp/com.mp.ShowMap}: java.lang.NullPointerException
  E/AndroidRuntime(  347):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
  E/AndroidRuntime(  347):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
  E/AndroidRuntime(  347):    at android.app.ActivityThread.access$2300(ActivityThread.java:125)
  E/AndroidRuntime(  347):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
  E/AndroidRuntime(  347):    at android.os.Handler.dispatchMessage(Handler.java:99)
  E/AndroidRuntime(  347):    at android.os.Looper.loop(Looper.java:123)
  E/AndroidRuntime(  347):    at android.app.ActivityThread.main(ActivityThread.java:4627)
  E/AndroidRuntime(  347):    at java.lang.reflect.Method.invokeNative(Native Method)
  E/AndroidRuntime(  347):    at java.lang.reflect.Method.invoke(Method.java:521)
  E/AndroidRuntime(  347):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
  E/AndroidRuntime(  347):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
  E/AndroidRuntime(  347):    at dalvik.system.NativeStart.main(Native Method)
  E/AndroidRuntime(  347): Caused by: java.lang.NullPointerException
  E/AndroidRuntime(  347):    at com.mp.ShowMap.onCreate(ShowMap.java:46)
  E/AndroidRuntime(  347):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
  E/AndroidRuntime(  347):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
  E/AndroidRuntime(  347):    ... 11 more
  </code></pre>