projects/positioning/app/src/main/res/layout/activity_ultrasound.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:orientation="vertical"
    tools:context="io.v.positioning.UltrasoundActivity">

    <Button
        android:id="@+id/send_ultrasound"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onSendUltrasound"
        android:text="@string/send_ultrasound" />

    <Button
        android:id="@+id/receiving_ultrasound"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="onToggleReceivingUltrasound"
        android:text="@string/start_receiving_ultrasound" />

</LinearLayout>