<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:orientation="vertical"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:gravity="bottom|center_vertical"    android:paddingBottom="@dimen/activity_vertical_margin"    android:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    tools:context=".MainActivity" >    <Button        android:id="@+id/bn1"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/bn1" />    <Button        android:id="@+id/bn2"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/bn2" />    <Button        android:id="@+id/bn3"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/bn3" />    <Button        android:id="@+id/bn4"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="@string/bn4" /></RelativeLayout>