<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="50dp"
        android:layout_height="30dp"
        android:background="#ff0000"
        android:gravity="center"
        android:text="mainService"
        android:textSize="20dp"
        android:textStyle="bold" />

</android.support.constraint.ConstraintLayout>