projects/positioning/app/src/main/res/layout/activity_main.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:orientation="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:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:onClick="onRecordMyLocation"
        android:text="@string/record_my_location" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:onClick="onFindAndRecordDevices"
        android:text="@string/find_and_record_devices" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:onClick="onUltrasound"
        android:text="@string/ultrasound" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:onClick="onBle"
        android:text="@string/ble" />

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:onClick="onTofProtocol"
        android:text="@string/tof_protocol" />

</LinearLayout>