为什么我们需要Observer.from（）

Question

I am learning RxJava in Android. I am following this tutorial here: http://plavatvornica.com/rxjava-for-beginners/

as shown in the code below,i created an observable that emits the items in a list one by onError

I have a question to deepn my understaning of the usage of RxJava libarary. the questio is, why do I need to use RxJava to gt items from a list one by one? i could do the same think using a loop!! since RxJava library offers such feature,I believe it should have ensued due to a specific need.

can you please help me to understand it

code

Subscriber listSubscriber = new Subscriber<String>() {
    @Override
    public void onCompleted() {
        Log.i(TAG, "I am done");
    }

    @Override
    public void onError(Throwable e) {
        Log.e(TAG, e.getMessage().toString());
    }

    @Override
    public void onNext(String s) {
        Log.i(TAG, "onNext: " + s);

    }
};

 //list as observable
    List<String> list = new ArrayList<>();
    list.add("1");
    list.add("2");
    list.add("3");
    list.add("4");
    Observable myObservable3 = Observable.from(list);

    myObservable3.subscribe(listSubscriber);

Answer 1

It comes from the idea of Reactive Programming: nothing is hopping until you sent a message, ie in the real application the data will never be requested until you subscribe to the observer. Your example, particularly, doesn't express this idea. But, if it would be, for example, database fetching, then it would be helpful. Moreover, reactive programming especially nice when async programming, because allows process data by part directly it was received without idle.