admobadapter/src/main/java/com/clockbyte/admobadapter/AdmobFetcherBase.java
protected void onAdFailed(final int adIdx, final int errorCode, final Object adPayload) {
        final Context context = mContext.get();
        //context may be null if activity is destroyed
        if(context != null) {
            for (AdmobListener listener : mAdNativeListeners)
                listener.onAdFailed(adIdx, errorCode, adPayload);
        }
    }
protected void onAdFailed(final int adIdx, final int errorCode, final Object adPayload) {
        final Context context = mContext.get();
        //context may be null if activity is destroyed
        if(context != null) {
            for (AdmobListener listener : mAdNativeListeners)
                listener.onAdFailed(adIdx, errorCode, adPayload);
        }
    }
Notifies all registered {@link AdmobListener} on a failed ad.