I hope you have images for these buttons directly. Thus, this attribute is textuseless. Use RelativeLayoutfor easy design of such screens.
Below I have attached the code. Please take a look and add a comment if there is any problem.
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent" android:layout_height="fill_parent"
android:gravity="center_horizontal">
<ImageButton android:id="@+id/btn_Show"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:background="@drawable/cmd_result_show" />
<ImageButton android:id="@+id/btn_showAll"
android:layout_toRightOf="@id/btn_Show" android:layout_width="wrap_content"
android:layout_height="wrap_content" android:background="@drawable/cmd_result_details" />
</RelativeLayout>