Didn't find class "androidx.core.content.FileProvider"

It seems that this error came from incomplete configuration of MultiDex in your app. Here you may find the similar issue and here is an article answering it.

I suggest you to check the following (extending App class helped me):

Your Application class (App.class, for instance, if you use it) should extend from MultiDexApplication class:

public class BaseApplication extends MultiDexApplication {}

or if you don't use Application class check your manifest:

<?xml version="1.0" encoding="utf-8"?>
    <manifest xmlns:android="http://schemas.android.com/apk/res/android"
        package="com.example.android.multidex.myapplication">
        <application
            ...
            android:name="android.support.multidex.MultiDexApplication">
            ...
        </application>
    </manifest>