title: "the method getSupportFragmentManager() is undefined for the type MainActivity"
body: <p>I apologize if I'm missing something simple here, but this is my first time using java and I'm stumped. </p>
  
  <pre><code>    public class MainActivity extends DroidGap {
        @Override
        public void onCreate(Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          super.loadUrl("file:///android_asset/www/index.html");
  
      if (savedInstanceState == null) {
          getSupportFragmentManager().beginTransaction()
                  .add(R.id.container, new PlaceholderFragment())
                  .commit();
      }
  }
  </code></pre>
  
  <p>The error message I get:</p>
  
  <pre><code>    The method getSupportFragmentManager() is undefined for the type MainActivity
  </code></pre>
  
  <p>thanks</p>