projects/syncpingpong/PingPongApp/app/src/main/res/layout/content_main.xml

<?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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="io.v.pingpongapp.MainActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <TextView
            android:id="@+id/debug_text"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Pinger: Hello World!" />

        <Button
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="@string/pingpongtoggle"
            android:onClick="pingpongToggle" />

        <Button
            android:id="@+id/useproxybutton"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="@string/useproxybutton"
            android:onClick="useProxy" />

        <Button
            android:id="@+id/pingpongbutton"
            android:layout_height="wrap_content"
            android:layout_width="wrap_content"
            android:text="@string/pingpongbegin"
            android:onClick="startTestPingPong" />
    </LinearLayout>


</RelativeLayout>