<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    android:gravity="center"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="50dp">

    <ProgressBar
        android:id="@+id/progressbar"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_gravity="center"
        android:visibility="visible" />

</LinearLayout>