ClassNotFoundException: Didn't find class "android.support.v4.content.FileProvider" after androidx migration

I'm trying to move to migrate to androidx. I used the migration tool in Android Studio. When I do this I get the following stacktrace when I run my app.

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.peerke.outdoorpuzzlegame.debug, PID: 10901
    java.lang.RuntimeException: Unable to get provider android.support.v4.content.FileProvider: java.lang.ClassNotFoundException: Didn't find class "android.support.v4.content.FileProvider" on path: DexPathList[[zip file "/data/app/com.peerke.outdoorpuzzlegame.debug-IBtFsngoLqc-cQb_hOO5wQ==/base.apk"],nativeLibraryDirectories=[/data/app/com.peerke.outdoorpuzzlegame.debug-IBtFsngoLqc-cQb_hOO5wQ==/lib/x86, /system/lib]]
        at android.app.ActivityThread.installProvider(ActivityThread.java:6376)
        at android.app.ActivityThread.installContentProviders(ActivityThread.java:5932)
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5847)
        at android.app.ActivityThread.access$1000(ActivityThread.java:198)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1637)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6649)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:826)
     Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v4.content.FileProvider" on path: DexPathList[[zip file "/data/app/com.peerke.outdoorpuzzlegame.debug-IBtFsngoLqc-cQb_hOO5wQ==/base.apk"],nativeLibraryDirectories=[/data/app/com.peerke.outdoorpuzzlegame.debug-IBtFsngoLqc-cQb_hOO5wQ==/lib/x86, /system/lib]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:125)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at android.app.AppComponentFactory.instantiateProvider(AppComponentFactory.java:121)
        at androidx.core.app.CoreComponentFactory.instantiateProvider(CoreComponentFactory.java:62)
        at android.app.ActivityThread.installProvider(ActivityThread.java:6360)
        at android.app.ActivityThread.installContentProviders(ActivityThread.java:5932) 
        at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5847) 
        at android.app.ActivityThread.access$1000(ActivityThread.java:198) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1637) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6649) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:493) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:826) 

The exception is correct. android.support.v4.content.FileProvider doesn't exist in my app. But androidx.core.content.FileProvider is included in my app. The big question is why does it want to load the old version of FileProvider?

Thanks to @CommonsWare

More explanation:

What to do, find the android.support.v4.FileProvider in your <provider> in AndroidManifest.xml.

Change it to androidx.core.content.FileProvider

In manifiest.xml file simply change this

<provider
        android:name="android.support.v4.content.FileProvider"
      .....
</provider>

To this one

<provider
    android:name="androidx.core.content.FileProvider"
    ......
</provider>

Or Simply

• Go to Refactor (Studio -> Menu -> Refactor)
• Click the Migrate to AndroidX.
• it's working.

> why does it want to load the old version of FileProvider?

Based on the stack trace, perhaps you are still using the old package name in the <provider> element in the manifest.