activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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/button2"
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:text="two" 
        android:layout_centerInParent="true"
        android:background="#F58675"
        android:layout_marginTop="10dp"
        android:layout_marginBottom="10dp"/>
    
    <Button
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:text="one"
        android:layout_above="@id/button2"
        android:background="#BDA786"/>
    
    <Button
        android:layout_width="match_parent"
        android:layout_height="90dp"
        android:text="three"
        android:layout_below="@id/button2"
        android:background="#C24E61"
         />

</RelativeLayout>