title: Android: Center ImageButton in LinearLayout
body: <p>How can I center ImageButton in the this LinearLayout</p>
  
  <pre><code>&lt;LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:background="@drawable/main"
  &gt;
  </code></pre>
  
  <p>ImageButton</p>
  
  <pre><code>              &lt;ImageButton android:id="@+id/btnBut"
                        android:background="@drawable/button"
                        android:layout_width="wrap_content"
                        android:layout_height="wrap_content" /&gt;
  </code></pre>
  
  <p>I don't want to use fixed sizes.</p>
  
  <p>Thanks</p>