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RxAndroid Subscribe code never called

I'm fairly new to RxJava and RxAndroid, and while some things work, I'm now completely stumped by what I see as basic functionality not working.
I have a subscribe call on a Subject that never seems to run, and I can't figure out why:
public class PairManager implements DiscoveryManagerListener {
private Subscription wifiAvailableSubscription;
private Subscription debugSubscription;
private DiscoveryManager discoveryManager;
private AsyncSubject<Map<String, ConnectableDevice>> availableDevices;
public PairManager(Context appContext) {
DiscoveryManager.init(appContext);
discoveryManager = DiscoveryManager.getInstance();
discoveryManager.addListener(this);
availableDevices = AsyncSubject.<Map<String, ConnectableDevice>> create();
//
// This subscription doesn't work
//
debugSubscription = availableDevices
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Action1<Map<String, ConnectableDevice>>() {
#Override
public void call(Map<String, ConnectableDevice> stringConnectableDeviceMap) {
//
// This code is never run !
//
Timber.d(">> Available devices changed %s", stringConnectableDeviceMap);
}
}, new Action1<Throwable>() {
#Override
public void call(Throwable throwable) {
Timber.d("Subscription failed %s", throwable);
}
});
availableDevices.onNext(Collections.<String, ConnectableDevice>emptyMap());
wifiAvailableSubscription = ReactiveNetwork.observeNetworkConnectivity(appContext)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Action1<Connectivity>() {
#Override
public void call(Connectivity connectivity) {
if (connectivity.getState().equals(NetworkInfo.State.CONNECTED) && connectivity.getType() == ConnectivityManager.TYPE_WIFI) {
discoveryManager.start();
} else {
discoveryManager.stop();
availableDevices.onNext(Collections.<String, ConnectableDevice>emptyMap());
}
}
});
}
public AsyncSubject<Map<String, ConnectableDevice>> getAvailableDevices() {
return availableDevices;
}
#Override
public void onDeviceAdded(DiscoveryManager manager, ConnectableDevice device) {
Timber.d("onDeviceAdded %s", device);
availableDevices.onNext(manager.getAllDevices());
Timber.d("Sanity check %s", availableDevices.getValue());
}
// ...
}
Is there a way to debug what is going wrong? I have tried creating basic Observable.from-type calls and logging those, and that works as expected. The sanity check log in onDeviceAdded also prints and indicates that availableDevices has in fact updated as expected. What am I doing wrong?

I've found the issue, I've used AsyncSubjects which only ever emit values when they are Completed, where I expect the functionality of BehaviorSubjects.

From the doccumentation:
When Connectivity changes, subscriber will be notified. Connectivity can change its state or type.
You say:
I have a subscribe call on a Subject
A subject won't return te last value. I will only return a value when onNext is called. I assume the Connectivity never changes so it never fires.

Andorid rxJava: how to get data from cache and and the same time update it in the background?

I just start learning rxJava for Android and want to implement the common use case:
request data from cache and show to the user
request data from web
server update data in storage and automatically show it to the user
Traditionally on of the best scenarios was use CursorLoader to get data from cache, run web request in the separate thread and save data to the disk via content provider, content provider automatically notify the listener and CursorLoader autoupdate UI.
In rxJava I can do it by running two different Observers as you can see in code below, but I don't find the way how to combine this two calls into the one to reach my aim. Googling shows this thread but it looks like it just get data from the cache or data from the web server, but don't do both RxJava and Cached Data
Code snippet:
#Override
public Observable<SavingsGoals> getCachedSavingsGoal() {
return observableGoal.getSavingsGoals()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}
#Override
public Observable<SavingsGoals> getRecentSavingsGoal() {
return api.getSavingsGoals()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}
model.getCachedSavingsGoal().subscribe(new Observer<SavingsGoals>() {
#Override
public void onCompleted() {
// no op
}
#Override
public void onError(Throwable e) {
Log.e(App.TAG, "Failed to consume cached data");
view.showError();
}
#Override
public void onNext(SavingsGoals savingsGoals) {
Log.d(App.TAG, "Show the next item");
if (savingsGoals != null && !savingsGoals.getSavingsGoals().isEmpty()) {
view.showData(savingsGoals.getSavingsGoals());
} else {
view.showError();
}
}
});
model.getRecentSavingsGoal().subscribe(new Observer<SavingsGoals>() {
#Override
public void onCompleted() {
// no op
}
#Override
public void onError(Throwable e) {
Log.e(App.TAG, "Failed to consume data from the web", e);
view.showError();
}
#Override
public void onNext(SavingsGoals savingsGoals) {
if (savingsGoals != null && !savingsGoals.getSavingsGoals().isEmpty()) {
view.showData(savingsGoals.getSavingsGoals());
} else {
view.showError();
}
}
});
Also, the one of issues with current approach is cache and web data are not garranted to be run sequently. It is possible when outdated data will come as latest and override recent from web.
To solve this issue I implemented Observer merge with filtration by timestamp: it get data from cache, pass it to the next observer and if cache is outdated fire new call to the web - case for thread competition solved by the filtration with timestamps. However, the issue with this approach I can not return cache data from this Observable - I need to wait when both requests finish their work.
Code snippet.
#Override
public Observable<Timestamped<SavingsGoals>> getSavingGoals() {
return observableGoal
.getTimestampedSavingsGoals()
.subscribeOn(Schedulers.io())
.flatMap(new Func1<Timestamped<SavingsGoals>, Observable<Timestamped<SavingsGoals>>>() {
#Override
public Observable<Timestamped<SavingsGoals>> call(Timestamped<SavingsGoals> cachedData) {
Log.d(App.FLOW, "getTimestampedSavingsGoals");
return getGoalsFromBothSources()
.filter(filterResponse(cachedData));
}
})
.subscribeOn(AndroidSchedulers.mainThread());
}
private Func1<Timestamped<SavingsGoals>, Boolean> filterResponse(Timestamped<SavingsGoals> cachedData) {
return new Func1<Timestamped<SavingsGoals>, Boolean>() {
#Override
public Boolean call(Timestamped<SavingsGoals> savingsGoals) {
return savingsGoals != null
&& cachedData != null
&& cachedData.getTimestampMillis() < savingsGoals.getTimestampMillis()
&& savingsGoals.getValue().getSavingsGoals().size() != 0;
}
};
}
private Observable<Timestamped<SavingsGoals>> getGoalsFromBothSources() {
Log.d(App.FLOW, "getGoalsFromBothSources:explicit");
return Observable.merge(
observableGoal.getTimestampedSavingsGoals().subscribeOn(Schedulers.io()),
api.getSavingsGoals()
.timestamp()
.flatMap(new Func1<Timestamped<SavingsGoals>, Observable<Timestamped<SavingsGoals>>>() {
#Override
public Observable<Timestamped<SavingsGoals>> call(Timestamped<SavingsGoals> savingsGoals) {
Log.d(App.FLOW, "getGoalsFromBothSources:implicit");
return observableGoal.saveAllWithTimestamp(savingsGoals.getTimestampMillis(), savingsGoals.getValue().getSavingsGoals());
}
}))
.subscribeOn(Schedulers.io());
}
Do you know the approach to do this in one Observer?
Potential solution:
#Override
public Observable<SavingsGoals> getSavingGoals() {
return api.getSavingsGoals()
.publish(network ->
Observable.mergeDelayError(
observableGoal.getSavingsGoals().takeUntil(network),
network.flatMap(new Func1<SavingsGoals, Observable<SavingsGoals>>() {
#Override
public Observable<SavingsGoals> call(SavingsGoals savingsGoals) {
return observableGoal.saveAll(savingsGoals.getSavingsGoals());
}
})
)
)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}
Sorry, hot replacement in IDE hide the issue which this approach has: first one in case if network unavailable and cache thread completes first, the error will terminate whole merge (solved by mergeDelayError), second one is in case when cache is empty and returns first data from web request will not be return on subscriber. As you can see my method returns Observable after save and traditional merge as I shown in my code properly handle this case but takeUntil by some reason can not. Question is still open.

For first question : You can save the result from Network Result by using doOnNext Method, It would looks something like this
public Observable<NetworkResponse> getDataFromNetwork(
final Request request) {
return networkCall.doOnNext(networkResponse -> saveToStorage(networkResponse);
}
Now to combine the two results from both Storage and Online, the best way is to combine with publish and merge. I recommend watching this talk.
The code would look something like this
public Observable<Response> getData(final Request request) {
return dataService.getDataFromNetwork(request)
.publish(networkResponse -> Observable.merge(networkResponse, dataService.getDataFromStorage(request).takeUntil(networkResponse)));
}
Why use publish and merge you my ask? publish method makes the response accessible in the callback. takeUntil means that you will take the data from storage but you will stop it IF for some reason, network call is finished before accessing storage data is finished. This way, you can be sure that new data from network is always shown even if it's finished before getting old data from storage.
The last but not least, in your subscriber OnNext just add the items to the list. (list.clear and list.addAll) Or similar functions or in you case view.showData()
EDIT: For The call getting disrupted when there's an error from network, add onErrorResumeNext at the end.
public Observable<Response> getData(final Request request) {
return dataService.getDataFromNetwork(request)
.publish(networkResponse -> Observable.merge(networkResponse, dataService.getDataFromStorage(request).takeUntil(networkResponse)))
.onErrorResumeNext(dataService.getDataFromStorage(request);
}

I'd recommend to "listen" only to local data, and refresh it when API response came.
Let say for getting local data you have something like:
#Nonnull
public Observable<SomeData> getSomeDataObservable() {
return Observable
.defer(new Func0<Observable<SomeData>>() {
#Override
public Observable<SomeData> call() {
return Observable.just(getSomeData());
}
});
}
So you need to add PublishSubject that will emit every time, when local data was updated (refreshSubject):
#Nonnull
public Observable<SomeData> getSomeDataObservableRefreshable() {
return refreshSubject.startWith((Object)null).switchMap(new Func1() {
public Observable<T> call(Object o) {
return getSomeDataObservable();
}
}
}
Now you need to subscribe only to getSomeDataObservableRefreshable(), and each time when data came from API, you update it and make refreshSubject .onNext(new Object())
Also i'd recommend to take a look to rx-java-extensions lib, it has alot of "cool tools" for RxAndroid. For example solution for your problem would be:
#Nonnull
public Observable<SomeData> getSomeDataObservable() {
return Observable
.defer(new Func0<Observable<SomeData>>() {
#Override
public Observable<SomeData> call() {
return Observable.just(getSomeData());
}
})
.compose(MoreOperators.<SomeData>refresh(refreshSubject));
}

Observable android understanding

I'm trying to understand how the observer pattern works in Android.
I've created this method to load a sample list of object, pushing each items to the subscriber and loading it to into the recyclerview.
I don't understand why if i load 10 items everything is working fine, but if i load 100/1000 or in general more items, the recyclerView is empty and onNext, onComplete are not fired.
private Observable<AppInfo> getAppList() {
return Observable.create(new Observable.OnSubscribe<AppInfo>() {
#Override
public void call(Subscriber<? super AppInfo> subscriber) {
for (int i = 0; i<10; i++){
AppInfo appInfo = new AppInfo(
"Test item "+i,
ContextCompat.getDrawable(getApplicationContext(), R.mipmap.ic_launcher),
i
);
subscriber.onNext(appInfo);
}
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
});
}
And this is how i use the Observable:
Observable<AppInfo> appInfoObserver = getAppList();
appInfoObserver
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber<AppInfo>() {
#Override
public void onCompleted() {
Toast.makeText(getApplicationContext(), "App List Load Completed!", Toast.LENGTH_LONG).show();
}
#Override
public void onError(Throwable e) {}
#Override
public void onNext(AppInfo appInfo) {
if(mAppInfoList != null){
mAppInfoList.add(appInfo);
adapter.notifyItemInserted(appInfo.getAppPosition());
}
}
});
Thanks for the help and advices.

You're not logging errors so if anything goes wrong you won't know (in this case you are probably forcing a MissingBackpressureException from the observeOn operator by sending it more than it requested). To be clear, in the subscriber:
public void onError(Throwable e) {
// log or display error here!!
}
Don't use Observable.create at all if you can help it because you need to honour backpressure or combine it with .onBackpressureBuffer.
The exception is that Observable.create(new SyncOnSubscribe<T>(...)) is a good way to create an Observable if you can imagine your source as an iterator/enumeration.
To avoid using Observable.create in your example you could do this:
Observable
.range(0, 10)
.map(i -> new AppInfo(...))
or without lambda:
Observable
.range(0, 10)
.map(new Func1<Integer, AppInfo>() {
#Override
public AppInfo call(Integer n) {
return new AppInfo(...);
}
});

Maybe your code is to heavy and its loading sync. Try to load your code inside a new thread, maybe you can use the observeOn() (i dont know exactally how rxjava works, but my guess is that this function defines the thread where the event occurs).

Mock Retrofit Observable<T> response in Android Unit tests

I have an API interface and I'm testing a View that involves network calls.
#Config(emulateSdk = 18)
public class SampleViewTest extends RobolectricTestBase {
ServiceApi apiMock;
#Inject
SampleView fixture;
#Override
public void setUp() {
super.setUp(); //injection is performed in super
apiMock = mock(ServiceApi.class);
fixture = new SampleView(activity);
fixture.setApi(apiMock);
}
#Test
public void testSampleViewCallback() {
when(apiMock.requestA()).thenReturn(Observable.from(new ResponseA());
when(apiMock.requestB()).thenReturn(Observable.from(new ResponseB());
AtomicReference<Object> testResult = new AtomicReference<>();
fixture.updateView(new Callback() {
#Override
public void onSuccess(Object result) {
testResult.set(result);
}
#Override
public void onError(Throwable error) {
throw new RuntimeException(error);
}
});
verify(apiMock, times(1)).requestA();
verify(apiMock, times(1)).requestB();
assertNotNull(testResult.get());
}
}
For some reason apiMock methods are never called and verification always fails.
In my view I'm calling my api like this
apiV2.requestA()
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer());
What am I missing here?
Update #1:
After some investigation it appears that when in my implementation (sample above) I observeOn(AndroidSchedulers.mainThread()) subscriber is not called. Still do not know why.
Update #2:
When subscribing just like that apiV2.requestA().subscribe(new Observer()); everything works just fine - mock api is called and test passes.
Advancing ShadowLooper.idleMainLooper(5000) did nothing. Even grabbed looper from handler in HandlerThreadScheduler and advanced it. Same result.
Update #3:
Adding actual code where API is used.
public void updateView(final Callback) {
Observable.zip(wrapObservable(api.requestA()), wrapObservable(api.requestB()),
new Func2<ResponseA, ResponseB, Object>() {
#Override
public Object call(ResponseA responseA, ResponseB responseB) {
return mergeBothResponses(responseA, responseB);
}
}
).subscribe(new EndlessObserver<Object>() {
#Override
public void onError(Throwable e) {
Log.e(e);
listener.onError(e);
}
#Override
public void onNext(Object config) {
Log.d("Configuration updated [%s]", config.toString());
listener.onSuccess(config);
}
});
}
protected <T> Observable<T> wrapObservable(Observable<T> observable) {
return observable.subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread());
}

I'm still wrapping my head around how to properly use rxjava myself but I would try to modify your code so that you only observeOn(mainThread) on the final zipped Observable instead of doing it on both of the original request response's Observable. I would then verify if this affect the fact that you have to advance both Loopers or not.
To simply your tests and remove the need for Looper idling I would take the threading out of the equation since you don't need background processing when running tests. You can do that by having your Schedulers injected instead of creating them statically. When running your production code you'd have the AndroidSchedulers.mainThread and Schedulers.io injected and when running tests code you would inject Schedulers.immediate where applicable.
#Inject
#UIScheduler /* Inject Schedulers.immediate for tests and AndroidSchedulers.mainThread for production code */
private Scheduler mainThreadSched;
#Inject
#IOScheduler /* Inject Scheduler.immediate for tests and Schedulers.io for production code */
private Scheduler ioSched;
public void updateView(final Callback) {
Observable.zip(wrapObservable(api.requestA()), wrapObservable(api.requestB()),
new Func2<ResponseA, ResponseB, Object>() {
#Override
public Object call(ResponseA responseA, ResponseB responseB) {
return mergeBothResponses(responseA, responseB);
}
}
).observeOn(mainThreadSched)
.subscribe(new EndlessObserver<Object>() {
#Override
public void onError(Throwable e) {
Log.e(e);
listener.onError(e);
}
#Override
public void onNext(Object config) {
Log.d("Configuration updated [%s]", config.toString());
listener.onSuccess(config);
}
});
}
protected <T> Observable<T> wrapObservable(Observable<T> observable) {
return observable.subscribeOn(ioSched);
}

what version of rxjava are you using? I know there was some changes in the 0.18.* version regarding the ExecutorScheduler. I had a similar issue as you when using 0.18.3 where I wouldn't get the onComplete message because my subscription would be unsubscribe ahead of time. The only reason I'm mentioning this to you is that a fix in 0.19.0 fixed my issue.
Unfortunately I can't really explain the details of what was fixed, it's beyond my understanding at this point but if it turns out to be the same cause maybe someone with more understand could explain. Here's the link of what I'm talking about https://github.com/Netflix/RxJava/issues/1219.
This isn't much of an answer but more a heads up in case it could help you.

As #champ016 stated there were issues with RxJava versions that are lower than 0.19.0.
When using 0.19.0 the following approach works. Although still don't quite get why I have to advance BOTH loopers.
#Test
public void testSampleViewCallback() {
when(apiMock.requestA()).thenReturn(Observable.from(new ResponseA());
when(apiMock.requestB()).thenReturn(Observable.from(new ResponseB());
AtomicReference<Object> testResult = new AtomicReference<>();
fixture.updateView(new Callback() {
#Override
public void onSuccess(Object result) {
testResult.set(result);
}
#Override
public void onError(Throwable error) {
throw new RuntimeException(error);
}
});
ShadowLooper.idleMainLooper(5000);
Robolectric.shadowOf(
Reflection.field("handler")
.ofType(Handler.class)
.in(AndroidSchedulers.mainThread())
.get().getLooper())
.idle(5000);
verify(apiMock, times(1)).requestA();
verify(apiMock, times(1)).requestB();
assertNotNull(testResult.get());
}

Using Observable in custom Application subclass

Is it acceptable to create Rx Observables in custom Application subclass. Reason for doing is, I can create BehaviorSubject inside the Application and will ask for changes every 10 minutes from Server, every Activity or Fragment which subscribes to this Observable will get only last state of changes.
Question is whether this architecture could be considered safe in terms of application lifecycle handling and easy to use?
class CustomApplication extends Application {
...
BehaviorSubject<Friends> mFriends = new BehaviorSubject<Friends>;
public void createObservables() {
Observable.create(new Observable.OnSubscribe<Friends>() {
public void call(Subscriber<?> s) {
while(true) {
mFriends.onNext("randomFriendN");
sleep(10sec);
}
}
})
.subscribeOn(Schedulers.newThread())
.subscribe(new Observer<List<NewsCategory>>() {
public void onNext(Friends f) { //empty }
});
}
public BehaviorSubject<Friends> getFriends() {
return mFriends;
}
}
UPDATE:
Everytime when new activity created and it wants to get data it can get it ApplicationContext's BehaviorSubject then subscribe to it, and Subject will emit last emitted value;
Why I want to do like this? E.g. Lets say you have news items, you fetched news feed and you want to start background task which fetches news item full content, in that case I can start fetching data while you are scrolling news list, and when you click detailed activity, we can show it from already fetched, or just download it.

I think this is perfectly safe as long as createObservables() is only called once during application initialization. A few suggested changes...
I wouldn't expose the BehaviorSubject part of mFriends in the returned value from getFriends(). That way callers of getFriends() will not be tempted to call onNext(). Change it to:
public Observable<Friends> getFriends() {
return mFriends;
}
If you want to be super safe use .asObservable() and callers will not even be able to cast the return value back to a BehaviorSubject.
public Observable<Friends> getFriends() {
return mFriends.asObservable();
}
I would also update your createObservable() method to call the BehaviorSubject onNext() from the subscribe callback. Here is your code slightly modified to use NewsItems.
BehaviorSubject<List<NewsItem>> mNewsItemSubject = BehaviorSubject.create();
void createObservables() {
Observable
.timer(10, 10, TimeUnit.SECONDS, Schedulers.newThread())
.flatMap(new Func1<Long, Observable<List<NewsItem>>>() {
#Override
public Observable<List<NewsItem>> call(Long aLong) {
// Normally you would create a network API that returns Observable<NewsItem>.
// For now just pretend this returned Observable makes an Observable
// network request.
return Observable.just(
Arrays.asList(
new NewsItem("fakeNewsItem"),
new NewsItem("fakeNewsItem1")
)
);
}
})
.subscribe(new Action1<List<NewsItem>>() {
#Override
public void call(List<NewsItem> newsItems) {
mNewsItemSubject.onNext(newsItems);
}
});
}
public Observable<List<NewsItem>> observeNewsItems() {
return mNewsItemSubject;
}
Your Android Activities can then call ((CustomApplication)getApplication()).observeNewsItems() to get the latest news items and any updates while the Activity is visible.
final Observable<List<NewsItem>> newsItemsObservable =
((CustomApplication) getApplication()).observeNewsItems();
newsItemsObservable
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Observer<List<NewsItem>>() {
#Override
public void onCompleted() {
// All done.
}
#Override
public void onError(Throwable e) {
// Notify user of error (maybe)
}
#Override
public void onNext(List<NewsItem> newsItems) {
// Update the UI with newsItems.
}
});