Navigation in MVi

Consider such a demand：Click the button to post data to the server and then navigate to the other Activity when request success. I modified the ProductDetailsPresenter and ProductDetailsActivity to provide some test for me.

I add a testBtnIntent() method for the ProductDetailsView to handle a click intent.

public class ProductDetailsActivity extends MviActivity<ProductDetailsView, ProductDetailsPresenter>
    implements ProductDetailsView {

    @Override
    public Observable<Boolean> testBtnIntent() {
      return RxView.clicks(btnTest).share().map(it -> true);;
    }

    @Override public void render(ProductDetailsViewState state) {
    Timber.d("render " + state);

    if (state instanceof ProductDetailsViewState.LoadingState) {
      renderLoading();
    } else if (state instanceof ProductDetailsViewState.DataState) {
      renderData((ProductDetailsViewState.DataState) state);
    } else if (state instanceof ProductDetailsViewState.ErrorState) {
      renderError();
    } else if (state instanceof ProductDetailsViewState.TestViewState) {
      TestClickActivity.start(this);
    } else {
      throw new IllegalStateException("Unknown state " + state);
    }
  }
}

And then mergeWith the loadDetails method

 @Override protected void bindIntents() {
    ...
    Observable<ProductDetailsViewState> loadDetails =
        intent(ProductDetailsView::loadDetailsIntent)
            .doOnNext(productId -> Timber.d("intent: load details for product id = %s", productId))
            .flatMap(interactor::getDetails)
            .observeOn(AndroidSchedulers.mainThread());

    Observable<ProductDetailsViewState> clickTest =
        intent(ProductDetailsView::testBtnIntent)
        .map((aBoolean) ->  new ProductDetailsViewState.TestViewState());

    subscribeViewState(loadDetails.mergeWith(clickTest), ProductDetailsView::render);
  }

Because the viewStateBehaviorSubject will reemit the latest viewstate , so it will always reemit the clickTest when I go back the previous page and the TestClickActivity will open again and again, The expected should be to go back to the previous page without reemit the click event. Sorry for my bad English. hope I can explanation of this. And can you give me some suggestion？

[sockeqwe]

Jfyi: I have figured out a simple pattern of how to do navigation properly (not only MVI related, but works well with MVI).

I can share it next week as I’m going to present it on a Meetup next Monday.

Stay tuned.

Andy Byrnes [e-mail] schrieb am Mi., 11. Apr. 2018, 06:22:

Would it be feasible to allow certain View States to be consumed instead of replacing the previous one?

@skykelsey https://github.com/skykelsey For this I’ve been having a dummy state that gets emitted by navigation intents (I call it NoOp) and is just filtered out to avoid any unnecessary renderings:

val intent1 = intent(…)val intent2 = intent(…) val viewStateObservable = Observable.merge(intent1, intent1).filter { it !is NoOp } subscribeViewState(viewStateObservable, View::render)

This, however, doesn’t solve the main problem at hand, for which I still haven’t come up with an elegant solution, unfortunately. It doesn’t seem like Mosby is well equipped to handle navigation in the presentation layer. So in the meantime I’ve implemented a base presenter that inherits from MviPresenter and hacks away at its implementation details to retrieve the previous view state, if it exists, and directly notify the view that a navigation event has occurred. This, combined with filtering out NoOp view states, has yet to cause me any issues.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/sockeqwe/mosby/issues/261#issuecomment-380322785, or mute the thread https://github.com/notifications/unsubscribe-auth/AAjnrgjDcIoSd1TIj7nYK38vlE5ctmrdks5tnYUegaJpZM4ONlOH .

[sockeqwe]

Here you go: http://hannesdorfmann.com/android/mosby3-mvi-8

Hope someone find it helpful.