LottieSample/src/main/res/layout/activity_qrscan.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"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.dlazaro66.qrcodereaderview.QRCodeReaderView
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:id="@+id/qrdecoderview"
        android:layout_width="0dp"
        android:layout_height="0dp" />

    <TextView
        app:layout_constraintVertical_bias="0.1"
        android:id="@+id/textScanPrompt"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintBottom_toTopOf="parent"
        android:maxWidth="220dp"
        android:gravity="center"
        android:textColor="#fff"
        android:text="@string/scan_prompt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />


    <ImageView
        android:id="@+id/scannerOverlay"
        app:layout_constraintVertical_bias="0.4"
        app:layout_constraintTop_toBottomOf="@+id/textScanPrompt"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        android:layout_width="200dp"
        android:layout_height="200dp"
        app:srcCompat="@drawable/ic_qr_overlay" />


</android.support.constraint.ConstraintLayout>