Flutter: Native Ads Error: Cannot find symbol

Question

I'm trying to set up Admob Native ads on Flutter following the official documentation, however for my surprise, nothing seems to work because I keep getting the same error:

Copy (12-error)\android\app\src\main\java\com\app\appname\adFactoryExample.java:47: error: cannot find symbol
    adView.setIconView(adView.findViewById(R.id.ad_app_icon));

This issue seems common so obviously, I tried the popular solutions including "flutter clean", changing the "android/app/build.gradle" file to 31 and add: android.useAndroidX=true android.enableJetifier=true to the "gradle.properties" file.

But nothing worked and I'm still having the same frustrating problem!