Ad unit overview

private InterstitialBuilder interstitialBuilder;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // Preload the AppBrain interstitial. Settings the AdId is optional,
    // but highly recommended. You can also create a custom AdId for your
    // publisher app on our dashboard under "Ad settings".
    interstitialBuilder = InterstitialBuilder.create()
        .setAdId(AdId.LEVEL_COMPLETE)
        .setOnDoneCallback(new Runnable() {
            @Override
            public void run() {
                // Preload again, so we can use interstitialBuilder again.
                interstitialBuilder.preload(getContext());
                loadNextLevel();
            })
        .preload(this);
}

public void onLevelCompleted() {
    interstitialBuilder.show(this);
}