Adding a banner element to the layout

In the layout file, associated with the activity where the banner will be shown, ad this AdManagerAdView element.

<com.google.android.gms.ads.admanager.AdManagerAdView
    android:id="@+id/adManagerAdView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_centerHorizontal="true"
    app:adSize="300x250"
    app:adUnitId="AD_UNIT_ID"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"/>

AD_UNIT_ID is a placeholder for ad unit ID. The banner will be constrained to the bottom of the layout and centered horizontally. Ad size and ad unit ID are necessary for the banner to be shown.

Banner

In the class, associated with the activity where the banner will be shown, add a method for banner ad. Banner parameters are used to customize the bid request. The values that can be choosen from are Signals.Api.MRAID_1, Signals.Api.MRAID_2, Signals.Api.MRAID_3 and Signals.Api.OMID_1.

public void createBannerAd(Context context) {
    bannerAdUnit = new BannerAdUnit(CONFIG_ID, WIDTH, HEIGHT);
    BannerParameters parameters = new BannerParameters();
    parameters.setApi(Arrays.asList(Signals.Api.OMID_1, Signals.Api.MRAID_3));
    bannerAdUnit.setBannerParameters(parameters);
    
    bannerAdUnit.setAutoRefreshInterval(30);
    
    final AdManagerAdView gamView = new AdManagerAdView(context);
    gamView.setAdUnitId(AD_UNIT_ID);
    gamView.setAdSizes(new AdSize(WIDTH, HEIGHT));
    
    ViewGroup container = findViewById(R.id.adManagerAdView);
    container.addView(gamView);
    gamView.setAdListener(bannerListener(gamView));
    
    final AdManagerAdRequest.Builder bannerBuilder = new AdManagerAdRequest.Builder();
    
    bannerAdUnit.fetchDemand(bannerBuilder, resultCode -> {
        AdManagerAdRequest request = bannerBuilder.build();
        gamView.loadAd(request);
    });
}

The context that is passed to this method is the class where the banner will be displayed. bannerAdUnit is a BannerAdUnit object; to initialize it, use CONFIG_ID, and the desired banner size, eg. 300x250. The setAutoRefreshInterval is a method for refreshing banners, where the minimum refresh time is 30 seconds, and the maximum is 120 seconds.
BannerParameters are used to customize bid requests. AdManagerAdView is created per Google Ad Manager documentation. Using addView, the banner is attached to the banner slot in the layout file, and, using fetchDemand, a bid request is made to the Prebid Server.

Ad listener

Ad listener is used to check whether the ad was successfully loaded. In addition, the findPrebidCreativeSize method is used to resize the ad.

private AdListener bannerListener(AdManagerAdView gamView) {
    return new AdListener() {
        @Override
        public void onAdLoaded() {
            Log.d(Tag, "Banner ad loaded successfully");
            AdViewUtils.findPrebidCreativeSize(gamView, new AdViewUtils.PbFindSizeListener() {
                @Override
                public void success(int width, int height) {
                    gamView.setAdSizes(new AdSize(width, height));
                    Log.d(Tag, "Creative size: " + width + "x" + height);
                }
                
                @Override
                public void failure(@NonNull PbFindSizeError error) {
                    Log.e(Tag, "Failed to find creative size: " + error.getDescription());
                }
            });
        }
        @Override
        public void onAdFailedToLoad(@NonNull LoadAdError adError) {
            Log.e(Tag, "Failed to load banner ad: " + adError.getMessage());
        }
    };
}

Pausing and resuming auction

It is necessary to stop the auction when leaving an activity where the banner ad is displayed because if not stopped, the auction continues happening, and displaying ads that are not seen by anyone which produces incorrect viewability results. After coming back to the activity where the auction was stopped, it can be resumed using resumeAutoRefresh().

@Override
protected void onStop() {
    super.onStop();
    if (bannerAdUnit != null) {
        Log.d(Tag, "Pausing auction");
        bannerAdUnit.stopAutoRefresh();
    }
}

@Override
protected void onPause() {
    super.onPause();
    if (bannerAdUnit != null) {
        Log.d(Tag, "Pausing auction");
        bannerAdUnit.stopAutoRefresh();
    }
}

@Override
protected void onResume() {
    super.onResume();
    if (bannerAdUnit != null) {
        Log.d(Tag, "Resuming auction");
        bannerAdUnit.resumeAutoRefresh();
    }
}

Destroying ad

Add an onDestroy() method for the banner to be destroyed with the activity.

@Override
protected void onDestroy() {
    super.onDestroy();
    if (bannerAdUnit != null) {
        bannerAdUnit.stopAutoRefresh();
        bannerAdUnit = null;
    }
}