Ad Size and Ad unit id must be set before loadAd is called

Question

I have this in my main xml file:

Answer 1

I faced that same problem because i do not add this line on xmlns:ads="http://schemas.android.com/apk/res-auto" top of . Then i change my xml code like this

after that i add this 3 line in onCreate method

AdView mAdView = (AdView)findViewById(R.id.adView);
    MobileAds.initialize(this, "ca-app-pub-3940256099942544~3347511713");
    AdRequest adRequest = new AdRequest.Builder().build();
    mAdView.loadAd(adRequest);