public void updateCacheCounter() {
        AndroidRxUtils.bindActivity(this, DataStore.getAllCachesCountObservable()).subscribe(countOfflineCaches -> {
            final TextView counter = findViewById(R.id.offline_counter);
            counter.setVisibility(countOfflineCaches > 0 ? View.VISIBLE : View.GONE);
            if (countOfflineCaches > 0) {
                counter.setText(getResources().getQuantityString(R.plurals.caches_stored_offline, countOfflineCaches, countOfflineCaches));
            }
        }, throwable -> Log.e("Unable to add cache count", throwable));
    }
prompts user if there's at least one blocked or failed download
main/src/main/java/cgeo/geocaching/MainActivity.java