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Banner ads custom events

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Complete the custom events setup.

Request a banner ad

When the custom event line item is reached in the waterfall mediation chain, the loadBanner:adConfiguration:completionHandler: method is called on the class name you provided when creating a custom event. In this case, that method is in SampleCustomEvent, which then calls the loadBanner:adConfiguration:completionHandler: method in SampleCustomEventBanner.

To request a banner ad, create or modify a class that implements GADMediationAdapter and loadBanner:adConfiguration:completionHandler:. If a class that extends GADMediationAdapter already exists, implement loadBanner:adConfiguration:completionHandler: there. Additionally, create a new class to implement GADMediationBannerAd.

In our custom event example, SampleCustomEvent implements the GADMediationAdapter interface and then delegates to SampleCustomEventBanner.


import GoogleMobileAds

class SampleCustomEvent: NSObject, GADMediationAdapter {

  fileprivate var bannerAd: SampleCustomEventBanner?

  func loadBanner(
    for adConfiguration: GADMediationBannerAdConfiguration,
    completionHandler: @escaping GADMediationBannerLoadCompletionHandler
  ) {
    self.bannerAd = SampleCustomEventBanner()
      for: adConfiguration, completionHandler: completionHandler)


#import "SampleCustomEvent.h"

@implementation SampleCustomEvent

SampleCustomEventBanner *sampleBanner;

- (void)loadBannerForAdConfiguration:
            (GADMediationBannerAdConfiguration *)adConfiguration
                                         completionHandler {
  sampleBanner = [[SampleCustomEventBanner alloc] init];
  [sampleBanner loadBannerForAdConfiguration:adConfiguration

SampleCustomEventBanner is responsible for the following tasks:

  • Loading the banner ad and invoking a GADMediationBannerLoadCompletionHandler method once loading completes

  • Implementing the GADMediationBannerAd protocol

  • Receiving and reporting ad event callbacks to the Google Mobile Ads SDK

The optional parameter defined in the Ad Manager UI is passed into your custom event as part of the loadBanner:adConfiguration:completionHandler: method. The parameter can be accessed through adConfiguration.credentials.settings[@"parameter"]. This parameter is typically an ad unit identifier that an ad network SDK requires when instantiating an ad object.


class SampleCustomEventBanner: NSObject, GADMediationBannerAd {
  /// The Sample Ad Network banner ad.
  var bannerAd: SampleBanner?

  /// The ad event delegate to forward ad rendering events to the Google Mobile Ads SDK.
  var delegate: GADMediationBannerAdEventDelegate?

  /// Completion handler called after ad load
  var completionHandler: GADMediationBannerLoadCompletionHandler?

  func loadBanner(
    for adConfiguration: GADMediationBannerAdConfiguration,
    completionHandler: @escaping GADMediationBannerLoadCompletionHandler
  ) {
    // Create the bannerView with the appropriate size.
    let adSize = adConfiguration.adSize
    bannerAd = SampleBanner(
      frame: CGRect(x: 0, y: 0, width: adSize.size.width, height: adSize.size.height))
    bannerAd?.delegate = self
    bannerAd?.adUnit = adConfiguration.credentials.settings["parameter"] as? String
    let adRequest = SampleAdRequest()
    adRequest.testMode = adConfiguration.isTestRequest
    self.completionHandler = completionHandler


#import "SampleCustomEventBanner.h"

@interface SampleCustomEventBanner () <SampleBannerAdDelegate,
                                       GADMediationBannerAd> {
  /// The sample banner ad.
  SampleBanner *_bannerAd;

  /// The completion handler to call when the ad loading succeeds or fails.
  GADMediationBannerLoadCompletionHandler _loadCompletionHandler;

  /// The ad event delegate to forward ad rendering events to the Google Mobile
  /// Ads SDK.
  id <GADMediationBannerAdEventDelegate> _adEventDelegate;

@implementation SampleCustomEventBanner

- (void)loadBannerForAdConfiguration:
            (GADMediationBannerAdConfiguration *)adConfiguration
                                         completionHandler {
  __block atomic_flag completionHandlerCalled = ATOMIC_FLAG_INIT;
  __block GADMediationBannerLoadCompletionHandler originalCompletionHandler =
      [completionHandler copy];

  _loadCompletionHandler = ^id<GADMediationBannerAdEventDelegate>(
      _Nullable id<GADMediationBannerAd> ad, NSError *_Nullable error) {
    // Only allow completion handler to be called once.
    if (atomic_flag_test_and_set(&completionHandlerCalled)) {
      return nil;

    id<GADMediationBannerAdEventDelegate> delegate = nil;
    if (originalCompletionHandler) {
      // Call original handler and hold on to its return value.
      delegate = originalCompletionHandler(ad, error);

    // Release reference to handler. Objects retained by the handler will also
    // be released.
    originalCompletionHandler = nil;

    return delegate;

  NSString *adUnit = adConfiguration.credentials.settings[@"parameter"];
  _bannerAd = [[SampleBanner alloc]
      initWithFrame:CGRectMake(0, 0, adConfiguration.adSize.size.width,
  _bannerAd.adUnit = adUnit;
  _bannerAd.delegate = self;
  SampleAdRequest *adRequest = [[SampleAdRequest alloc] init];
  adRequest.testMode = adConfiguration.isTestRequest;
  [_bannerAd fetchAd:adRequest];

Whether the ad is successfully fetched or encounters an error, you would call GADMediationBannerLoadCompletionHandler. In the event of success, pass through the class that implements GADMediationBannerAd with a nil value for the error parameter; in the event of failure, pass through the error you encountered.

Typically, these methods are implemented inside callbacks from the third-party SDK your adapter implements. For this example, the Sample SDK has a SampleBannerAdDelegate with relevant callbacks:


func bannerDidLoad(_ banner: SampleBanner) {
  if let handler = completionHandler {
    delegate = handler(self, nil)

func banner(
  _ banner: SampleBanner, didFailToLoadAdWith errorCode: SampleErrorCode
) {
  let error =
      code: SampleCustomEventErrorCodeSwift
        "Sample SDK returned an ad load failure callback with error code: \(errorCode)"
  if let handler = completionHandler {
    delegate = handler(nil, error)


- (void)bannerDidLoad:(SampleBanner *)banner {
  _adEventDelegate = _loadCompletionHandler(self, nil);

- (void)banner:(SampleBanner *)banner
    didFailToLoadAdWithErrorCode:(SampleErrorCode)errorCode {
  NSError *error = SampleCustomEventErrorWithCodeAndDescription(
      [NSString stringWithFormat:@"Sample SDK returned an ad load failure "
                                 @"callback with error code: %@",
  _adEventDelegate = _loadCompletionHandler(nil, error);

GADMediationBannerAd requires implementing a UIView property:


var view: UIView {
  return bannerAd ?? UIView()


- (nonnull UIView *)view {
  return _bannerAd;

Forward mediation events to the Google Mobile Ads SDK

Once you've called GADMediationBannerLoadCompletionHandler with a loaded ad, the returned GADMediationBannerAdEventDelegate delegate object can then be used by the adapter to forward presentation events from the third-party SDK to the Google Mobile Ads SDK. The SampleCustomEventBanner class implements the SampleBannerAdDelegate protocol to forward callbacks from the sample ad network to the Google Mobile Ads SDK.

It's important that your custom event forwards as many of these callbacks as possible, so that your app receives these equivalent events from the Google Mobile Ads SDK. Here's an example of using callbacks:


func bannerWillLeaveApplication(_ banner: SampleBanner) {


- (void)bannerWillLeaveApplication:(SampleBanner *)banner {
  [_adEventDelegate reportClick];

This completes the custom events implementation for banner ads. The full example is available on GitHub. You can use it with an ad network that is already supported or modify it to display custom event banner ads.