Retry a call with Retrofit 2 and RxJava2 after displaying a dialog

Question

I\'m calling an API using Retrofit 2 and RxJava2. If a call fails, in some cases (e.g. no Internet connection), I want to display an error dialog to the user and let him retry.<

Answer 1

final PublishSubject<Object> retrySubject = PublishSubject.create();

disposable.add(getData()
    .doOnError(throwable -> enableButton())
    .retryWhen(observable -> observable.zipWith(retrySubject, (o, o2) -> o))
    .subscribeWith(/* do what you want with the result*/)
}));

When button is clicked you trigger this event:

retrySubject.onNext(new Object());

As you can see in this Marble diagram:

the error is not propagated. The retryWhen operator will indeed handle it and do a proper action. This is the reason why you have to enable (or for example show a Dialog) in doOnError, before retryWhen operator.

When you don't want to listen anymore for successive retry attempts, you just need to unsubscribe:

disposable.dispose();

As per your question:

What should I do if I want to retry only on a specific Exception but not on the other ones?

You can modify your retryWhen in this way:

.retryWhen(throwableObservable -> throwableObservable.flatMap(throwable -> {
      if (throwable instanceof TargetException) {
          return Observable.just(throwable).zipWith(retrySubject, (o, o2) -> o);
      } else {
          throw Throwables.propagate(throwable);
      }
}))

Where Throwables.propagate(throwable) is a Guava util that can be replaced with throw new RuntimeException(throwable);

Answer 2

for me i am using clean architecture and it was hard to put android code to show dialog in usecase or repository. so since i was using kotlin i passed in a lamba to take care of things for me. something like this:

here is my full presenter:

 class WeatherDetailsPresenter @Inject constructor(var getCurrentWeatherWithForecastUsecase: GetCurrentWithForcastedWeatherUsecase) : BaseMvpPresenter<WeatherDetailsView>() {

    fun presentCurrentAndForcastedWeather(country: String?) {
        getCurrentWeatherWithForecastUsecase.takeUnless { country?.isBlank() == true }?.apply {
            this.countyName = country
            execute(object : DefaultSubscriber<Pair<CurrentWeatherModel, ForecastedWeatherModel>>() {
                override fun onSubscribe(d: Disposable) {
                    super.onSubscribe(d)
                    showLoading(true)
                }

                override fun onNext(t: Pair<CurrentWeatherModel, ForecastedWeatherModel>) {
                    super.onNext(t)
                    view?.showCurrentWeather(t.first)
                    view?.showForcastWeather(t.second)
                }

                override fun onError(e: Throwable) {
                    super.onError(e)
//if i get an error pass in lambda to the dialog
                    myErrorDialog.setretryAction( {this@WeatherDetailsPresenter.presentCurrentAndForcastedWeather(country)})
                }

                override fun onComplete() {
                    super.onComplete()
                    showLoading(false)
                }
            })
        } ?: run { view?.showCountryUnavailable() }
    }

then in then errordialog i do this assuming its a dialogfragment:

lateinit var retryAction: () -> Unit

override fun onStart() {
        super.onStart()
        dialog.window.setLayout(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.MATCH_PARENT)
        button.setOnClickListener { dismiss();retryAction() }
    }

my code for on error is not acutally like that but just to give you an idea on how to pass in a lambda. im sure you can pass in a function of your own. in this case the lambda was the method itself to retry.