zumo_2.0_android/app/src/main/res/layout/alert_dialog.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  xmlns:tools="http://schemas.android.com/tools"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:gravity="center"
  android:background="@color/colorAccent">

  <TextView
    android:id="@+id/text_alert_message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"/>
</LinearLayout>