Replace your XML with below code..
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<RelativeLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="#484848"
android:orientation="horizontal">
<TextView
android:id="@+id/windowtitle"
android:layout_width="fill_parent"
android:layout_centerInParent="true"
android:layout_height="wrap_content"
android:text="Support"
android:gravity="center_horizontal|center_vertical"
android:textSize="30sp" ></TextView>
<Button
android:id="@+id/syncbutton"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:layout_marginTop="3dip"
android:layout_alignParentRight="true"
android:text="Sync" />
</RelativeLayout>
</RelativeLayout>
Hope this work.....