activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout 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"
    tools:context=".MainActivity">

    <com.applandeo.materialcalendarview.CalendarView
        android:id="@+id/calendarView"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:headerColor="@color/colorPrimary"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:headerLabelColor="@color/colorAccent"
        app:todayLabelColor="@color/daysLabelColor"
        app:selectionColor="@color/design_default_color_primary_dark"
        app:abbreviationsBarColor="@color/colorAccent"
        app:daysLabelsColor="#FFF"
        app:pagesColor="@color/design_default_color_primary_dark"
        app:abbreviationsLabelsColor="@color/design_default_color_primary_dark"
        app:selectionLabelColor="@color/currentMonthDayColor"/>



    <android.support.design.widget.FloatingActionButton
        android:id="@+id/floatingActionButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginBottom="76dp"
        android:layout_marginRight="48dp"
        android:src="@drawable/ic_arrow_right"
        app:backgroundTint="@color/colorAccent"
        app:elevation="5dp"
        app:fabSize="normal"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintRight_toRightOf="parent" />

</android.support.constraint.ConstraintLayout>