compile 'com.google.android.gms:play-services-ads:8.4.0'

    BannerAds
    ca-app-pub-3940256099942544/6300978111

package com.example.test.bannerads;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;

public class MainActivity extends AppCompatActivity {
    private AdView adView;
    AdRequest adRequest;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        adView = (AdView) findViewById(R.id.ad_view);
        adRequest = new AdRequest.Builder().build();
        adView.loadAd(adRequest);


    }
    @Override
    public void onPause() {
        if (adView != null) {
            adView.pause();
        }
        super.onPause();
    }

    @Override
    public void onResume() {
        super.onResume();
        if (adView != null) {
            adView.resume();
        }
    }

    @Override
    public void onDestroy() {
        if (adView != null) {
            adView.destroy();
        }
        super.onDestroy();
    }
}