When to call dispose and clear on CompositeDisposable

Solution 1:

You're right, you can save yourself from creating a new CompositeDisposable for each time the corresponding view is created, but instead treat a CompositeDisposable as a single instance tied to the onCreate/onDestroy lifecycle methods and treat aggregated disposables as part of the fragment view calling clear in onDestroyView.

Solution 2:

Instead of using CompositeDisposable.dispose(), you can better use CompositeDisposable.clear() so you don't have to create a new CompositeDisposable: method documentation.

clear() //Atomically clears the container, then disposes all the previously contained Disposables.

dispose() //Dispose the resource, the operation should be idempotent.

Solution 3:

private final CompositeDisposable disposables = new CompositeDisposable();


// adding an Observable to the disposable
disposables.add(sampleObservable()
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribeWith(new DisposableObserver<String>() {
                    @Override
                    public void onComplete() {
                    }

                    @Override
                    public void onError(Throwable e) {
                    }

                    @Override
                    public void onNext(String value) {
                    }
                }));

    static Observable<String> sampleObservable() {
        return Observable.defer(new Callable<ObservableSource<? extends String>>() {
            @Override
            public ObservableSource<? extends String> call() throws Exception {
                // Do some long running operation
                SystemClock.sleep(2000);
                return Observable.just("one", "two", "three", "four", "five");
            }
        });
    }                


// Using clear will clear all, but can accept new disposable
disposables.clear(); 
// Using dispose will clear all and set isDisposed = true, so it will not accept any new disposable
disposables.dispose();