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

    <LinearLayout
        android:id="@+id/root"
        android:orientation="vertical"
        android:background="#FF888888"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

    </LinearLayout>

    <Button
        android:id="@+id/btn"
        android:text="@string/play"
        android:layout_centerInParent="true"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</RelativeLayout>