The ad size and ad unit ID must be set before loadAd when set programmatically

Question

I have no idea what is going on here but I am trying to set my ad unit ID dynamically through code like below and removing it from the XML but still get the error:

Answer 1

After trying,

1. Supply adunit ID and adsize from xml ONLY.
2. Supply adunit ID and adsize from .java file ONLY.

Problem is solved by

1. Removing xmlns:ads="http://schemas.android.com/apk/res-auto" line from root layout.

2. supply adunit ID and adsize as follows,

   app:adSize="SMART_BANNER" app:adUnitId="@string/banner_ad_unit_id"

   3. Clean and run app.