android_nework_observable.java

 public Observable<Intent> networkObservable() {
    return Observable.create(new Observable.OnSubscribe<Intent>() {
        @Override
        public void call(Subscriber<? super Intent> subscriber) {
            final BroadcastReceiver broadcastReceiver = new BroadcastReceiver() {
                @Override
                public void onReceive(Context context, Intent intent) {
                    subscriber.onNext(intent);
                }
            };

            final Subscription subscription = Subscriptions.create(new Action0() {
                @Override
                public void call() {
                    mContext.unregisterReceiver(broadcastReceiver);
                }
            });

            subscriber.add(subscription);
            mContext.registerReceiver(broadcastReceiver, mIntentFilter);
        }
    });
}

private boolean isNetworkAvailable() {
    ConnectivityManager cm = (ConnectivityManager) mContext.getSystemService(Context.CONNECTIVITY_SERVICE);
    NetworkInfo activeNetwork = cm.getActiveNetworkInfo();
    return activeNetwork != null;
}