AndroidRX - run method in background

Question

I created simple activity with infinity progres bar, and I\'am trying to run time consuming method using RxJava to prevent UI thread from blocking, but everytime UI thread is bl

Answer 1

Your doHeavyStuff() executes computation on calling thread, you just wrap your result into Observable. In order to wrap computation into observable you should use defer

Observable.defer(new Func0<Observable<Integer>>() {
    @Override
    public Observable<Integer> call() {
        return Observable.just(doHeavyStuff());
    }
});

then you can specify threads by subscribeOn and observeOn methods

Answer 2

Also, you can use RxJavaAsyncUtil:

compile 'io.reactivex:rxjava-async-util:0.21.0'

Code:

Observable.fromFunc0(() -> doHeavyStuff())

Answer 3

According to docs

Deprecated: fromFunc0 Unnecessary now that Func0 extends Callable. Just call fromCallable(java.util.concurrent.Callable) instead.

So you could make the call in this way:

Observable.fromCallable(new Callable<Object>() {
            @Override
            public Object call() throws Exception {
                return someMethod();
            }
        }).subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread()).subscribe(new Action1<Object>() {
                    @Override
                    public void call(Object object) {

                    }
                });

Answer 4

kotlin use below code to work in background

 Single.fromCallable {
                  // method that run in background

          }
           .subscribeOn(Schedulers.io())
           .observeOn(AndroidSchedulers.mainThread())
           .subscribe()

Answer 5

With RxJava2 a possible solution is:

Version with lambdas:

Single.fromCallable(() -> loadInBackground())
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe((resultObject) -> { updateUi(resultObject) });

Version without lambdas:

Single.fromCallable(new Callable<Object>() {
    @Override
    public Object call() throws Exception {
        return loadInBackground();
    }
})
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Consumer<Object>() {
    @Override
    public void accept(Object resultObject) throws Exception {
        updateUi(resultObject);
    }
 });

Example methods used above:

private Object loadInBackground() {
    // some heavy load code
    return resultObject;
}

private void updateUi(Object resultObject) {
    // update your Views here
}