CODEWITHSUNDEEP
javaandroidrx-java
ikiton
ikiton

Reputation: 45

RxJava Single.just in main thread

This code begining in main thread, but i use subscribeOn and observeOn on Schedulers.io

  disposableBag.add(Single.just(HardOperation.get())
            .doOnSuccess(it -> {
                Log.i("123", Thread.currentThread() + " current"); // Thread[RxCachedThreadScheduler-1,5,main]
            })
            .subscribeOn(Schedulers.io())
            .observeOn(Schedulers.io()).subscribe(it -> {
                adapter.set(it);
                progressBar.setVisibility(View.GONE);
            }));

if i use this sample

disposableBag.add(Single
                .create((SingleOnSubscribe<List<Info>>) emitter -> {
                    emitter.onSuccess(HardOperation.get());
                })
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread()).subscribe(it -> {
                    adapter.set(it);
                    progressBar.setVisibility(View.GONE);
                }));

it works nice

Upvotes: 0

Views: 1316

Answers (1)

Daniel
Daniel

Reputation: 400

I think you are asking why HardOperation.get() runs on main thread when called inside Single.just().

The reason is you are creating a Single (subclass of Observable) using Single.just(). The code is evaluated from inside out, from inner most expression out. So, HardOperation.get() is called first before being passed to Single.just(). HardOperation.get() will then take a while to complete and block the entire programs execution, before RxJava has a chance to do work on a different thread.

The difference of the second code snippet is that Single.create((SingleOnSubscribe<List<Info>>) emitter -> {emitter.onSuccess(HardOperation.get());}) creates a Single by taking in an object that produces or emits a HardOperation.get(). Creating this producer object is fast. Notice that emitter.onSuccess(HardOperation.get()) is not immediately called. The producer is created and given to Single.create(). It is RxJava's job to call the producer wrapped in the Single on a different thread, which then calls HardOperation.get() without blocking.

Upvotes: 2

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