wulkanowy-mod/app/src/main/res/layout/fragment_grade.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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.design.widget.TabLayout
        android:id="@+id/gradeTabLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/colorPrimary"
        android:elevation="5dp"
        android:visibility="invisible"
        app:tabGravity="fill"
        app:tabIndicatorColor="@android:color/white"
        app:tabMaxWidth="0dp"
        app:tabMode="fixed"
        app:tabTextColor="@android:color/white" />

    <android.support.v4.view.ViewPager
        android:id="@+id/gradeViewPager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_below="@id/gradeTabLayout"
        android:visibility="invisible" />

    <ProgressBar
        android:id="@+id/gradeProgress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:indeterminate="true" />
</RelativeLayout>