title: Android java.lang.RuntimeException: Unable to instantiate activity ComponentInfo ... java.lang.NullPointerException
body: <p>For some reason, I keep on getting the following error every time I try to launch my application:</p>
  
  <pre><code>Unable to instantiate activity ComponentInfo{com.example.lifeahead/com.example.lifeahead.MainActivity}:java.lang.NullPointerException
  </code></pre>
  
  <p>I checked my manifest file and every activity has been added. </p>
  
  <p>The only method I use when I start the application up is:</p>
  
  <pre><code>private void logIn(){
      Button logIn = (Button) findViewById(R.id.login);
      logIn.setOnClickListener(new View.OnClickListener() {
  
          @Override
          public void onClick(View v) {
              // TODO Auto-generated method stub
              Intent loginIntent = new Intent(MainActivity.this, HomeActivity.class);
              loginIntent.putExtra("cmUN", cmUN);
              loginIntent.putExtra("cmPW", cmPW);
              startActivity(loginIntent);
          }
      });
  }
  </code></pre>
  
  <p>Here's the onCreate:</p>
  
  <pre><code>protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
  
      if (savedInstanceState == null) {
          getSupportFragmentManager().beginTransaction()
                  .add(R.id.container, new PlaceholderFragment()).commit();
      }
  
      logIn();
  }
  </code></pre>
  
  <p>Full log:</p>
  
  <p>E</p>
  
  <pre><code>/AndroidRuntime(1607): FATAL EXCEPTION: main
  E/AndroidRuntime(1607): Process: com.example.lifeahead, PID: 1607
  E/AndroidRuntime(1607): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.lifeahead/com.example.lifeahead.MainActivity}: java.lang.NullPointerException
  E/AndroidRuntime(1607):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2121)
  E/AndroidRuntime(1607):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
  E/AndroidRuntime(1607):     at android.app.ActivityThread.access$800(ActivityThread.java:135)
  E/AndroidRuntime(1607):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
  E/AndroidRuntime(1607):     at android.os.Handler.dispatchMessage(Handler.java:102)
  E/AndroidRuntime(1607):     at android.os.Looper.loop(Looper.java:136)
  E/AndroidRuntime(1607):     at android.app.ActivityThread.main(ActivityThread.java:5017)
  E/AndroidRuntime(1607):     at java.lang.reflect.Method.invokeNative(Native Method)
  E/AndroidRuntime(1607):     at java.lang.reflect.Method.invoke(Method.java:515)
  E/AndroidRuntime(1607):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
  E/AndroidRuntime(1607):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
  E/AndroidRuntime(1607):     at dalvik.system.NativeStart.main(Native Method)
  E/AndroidRuntime(1607): Caused by: java.lang.NullPointerException
  E/AndroidRuntime(1607):     at android.app.Activity.findViewById(Activity.java:1884)
  E/AndroidRuntime(1607):     at com.example.lifeahead.MainActivity.&lt;init&gt;(MainActivity.java:22)
  E/AndroidRuntime(1607):     at java.lang.Class.newInstanceImpl(Native Method)
  E/AndroidRuntime(1607):     at java.lang.Class.newInstance(Class.java:1208)
  E/AndroidRuntime(1607):     at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
  E/AndroidRuntime(1607):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2112)
  E/AndroidRuntime(1607):     ... 11 more
  </code></pre>
  
  <p>I appreciate all the help I can get!</p>