gistfile1.txt

private boolean isShowing;
    private final int maxChecks = 3;
    private int currentChecks = 0;
    
    protected void onCreate(Bundle savedInstanceState) {
        //...
        startChecking();
    }
    
    private void startChecking(){
        currentChecks = 0;
        checkAndShowAd();
    }
    private void checkAndShowAd(){
        if( isShowing ) return;
        Log.d("QWERTY", "checkAndShowAd() #"+currentChecks);
        boolean isAdReady = Enhance.isInterstitialReady();
//        isAdReady = false;
        if( isAdReady ){
            Log.d("QWERTY", "Ad is ready, show it!");
            showAd();
        }else{
            if( currentChecks + 1 > maxChecks ){
                Log.d("QWERTY", "max checks reached!");
                return;
            }
            currentChecks++;
            Log.d("QWERTY", "Ad is not ready, schedule next check.");
            Handler handler = new Handler();
            handler.postDelayed(new Runnable() {
                @Override
                public void run() {
                    checkAndShowAd();
                }
            }, 1000);
        }
    }
    private void showAd(){
        isShowing = true;
        Enhance.showInterstitialAd();
    }