OpenCV/opencv/samples/android/mobilenet-objdetect/res/layout/activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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="org.opencv.samples.opencv_mobilenet.MainActivity">

    <org.opencv.android.JavaCameraView
        android:id="@+id/CameraView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:visibility="visible" />
</FrameLayout>