ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
        scheduler.scheduleAtFixedRate(new Runnable() {

            public void run() {
                runOnUiThread(new Runnable() {
                    public void run() {

                        interstitialAd = new InterstitialAd(MainActivity.this);
                        interstitialAd.setAdUnitId(getString(R.string.admob_interstitial_id));
                        AdRequest adRequest = new AdRequest.Builder().build();
                        interstitialAd.loadAd(adRequest);
                        interstitialAd.setAdListener(new AdListener() {
                            public void onAdLoaded() {
                                if (interstitialAd.isLoaded()) {
                                    interstitialAd.show();
                                }
                            }
                        });

                    }
                });

            }
        }, 120, 120, TimeUnit.SECONDS);