title: Android - layout is defined in two seperate files?
body: <p>I found out that the layout of my activity is defined in two files. This is my main.xml in /res/menu:</p>
  
  <pre><code>&lt;menu xmlns:android="http://schemas.android.com/apk/res/android" &gt;
      &lt;android.support.v4.widget.DrawerLayout
          xmlns:android="http://schemas.android.com/apk/res/android"
          android:id="@+id/drawer_layout"
          android:layout_width="match_parent"
          android:layout_height="match_parent"&gt;
          &lt;!-- The main content view --&gt;
          &lt;FrameLayout
              android:id="@+id/content_frame"
              android:layout_width="match_parent"
              android:layout_height="match_parent" /&gt;
  
          &lt;!-- The navigation drawer --&gt;
          &lt;ListView android:id="@+id/left_drawer"
              style="@style/NavigationDrawer"/&gt;
  
              &lt;!--  android:layout_width="240dp"
              android:layout_height="match_parent"
              android:layout_gravity="start"
              android:choiceMode="singleChoice"
              android:divider="@android:color/transparent"
              android:dividerHeight="0dp"
              android:background="#111"/&gt; --&gt;
  
      &lt;/android.support.v4.widget.DrawerLayout&gt;
  
  
      &lt;item
          android:id="@+id/add_button"
          android:icon="@drawable/ic_action_new"
          android:title="@string/add_button"
          android:showAsAction="ifRoom"/&gt;
  
  &lt;/menu&gt;
  </code></pre>
  
  <p>And here you can find my activity_main.xml in the /res/layout/ subfolder. </p>
  
  <pre><code>&lt;android.support.v4.widget.DrawerLayout
      xmlns:android="http://schemas.android.com/apk/res/android"
      android:id="@+id/drawer_layout"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:background="@drawable/bg"&gt;
  
  
      &lt;!-- The main content view --&gt;
      &lt;FrameLayout
          android:id="@+id/content_frame"
          android:layout_width="match_parent"
          android:layout_height="match_parent" /&gt;
  
      &lt;!-- The navigation drawer --&gt;
      &lt;ListView android:id="@+id/left_drawer"
          style="@style/NavigationDrawer"/&gt;
  &lt;/android.support.v4.widget.DrawerLayout&gt;
  </code></pre>
  
  <p>As you can see, e.g. the navigation drawer is defined twice. Is that necessary? And do I have to write every change into both files?</p>