activity_map.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
    tools:context=".MapActivity">

    <fragment
        android:id="@+id/mapFragment"
        class="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <ImageButton
        android:id="@+id/currentLocationImageButton"
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_marginBottom="25dp"
        android:layout_marginEnd="15dp"
        android:contentDescription="@null"
        android:src="@drawable/current_location_vector_icon" />
</RelativeLayout>