1、处理权限问题

<uses-permission android:name="android.permission.CAMERA" />

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    <uses-feature
        android:name="android.hardware.camera"
        android:required="true" />
    <uses-feature
        android:name="android.hardware.camera.autofocus"
        android:required="true" />
    <uses-feature
        android:name="android.hardware.camera.front"
        android:required="true" />
    <uses-feature
        android:name="android.hardware.camera.front.autofocus"
        android:required="true" />

 2、动态权限处理

implementation 'io.reactivex.rxjava2:rxandroid:2.0.1'
    implementation 'io.reactivex.rxjava2:rxjava:2.0.5'
    implementation 'com.tbruyelle.rxpermissions2:rxpermissions:0.9.3@aar'

 3、open_cv人脸识别模型文件（复制图示第2步lbpcascade frontalface.xml到项目raw文件夹下，注意raw若无，请自己新建）

 4、页面布局如下

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FAFFFFFF"
    android:orientation="vertical">

    <org.opencv.android.JavaCameraView
        android:id="@+id/by"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="#00000000" />

</LinearLayout>