app/src/main/res/layout/activity_main.xml

   1 <?xml version="1.0" encoding="utf-8"?>
   2 <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
   3     xmlns:app="http://schemas.android.com/apk/res-auto"
   4     xmlns:tools="http://schemas.android.com/tools"
   5     android:layout_width="match_parent"
   6     android:layout_height="match_parent"
   7     android:background="@android:color/background_dark"
   8     tools:context=".MainActivity">
   9
  10 </android.support.constraint.ConstraintLayout>