I tried to use paging in my project. Unfortunately, it works not as I expected. I expected that the liveDataObserver will work after callBack.onResult.But in fact, the liveDataObserver observes immediately when the loadInitial finished.The callBack works later, and didn't post data to the observer.
The code:
First I wrote a class extend PageKeyedDataSource and interface SingleCreator
public class MyPagingDataSource<T> extends PageKeyedDataSource<Integer, T>
public interface SingleCreator<T> {
SingleSubscribeProxy<Page<T>> createSingle(int page, int pageSize);
}
Then the constructor of MyPagingDataSource:
public MyPagingDataSource(SingleCreator<T> singleCreator) {
this.singleCreator = singleCreator;
}
And override loadInitial:
#Override
public void loadInitial(#NonNull LoadInitialParams<Integer> params, #NonNull LoadInitialCallback<Integer, T> callback) {
singleCreator.createSingle(1, params.requestedLoadSize)
.subscribe(new SingleObserver<Page<T>>() {
#Override
public void onSubscribe(Disposable d) {
}
#Override
public void onSuccess(Page<T> ts) {
callback.onResult(ts.list, ts.pageNumber, ts.total, ts.pageNumber - 1, ts.pageNumber + 1);
Timber.d("registerLiveData" + ts.list.size());
}
#Override
public void onError(Throwable e) {
e.printStackTrace();
}
});
try {
//when I add this, observer will work after callback
//And if not observer works before callback.onResult
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
Then the datasourceFactory is just newInstanced in viewModel:
public LiveData<PagedList<MyData>> page = loadPageData();
public LiveData<PagedList<MyData>> loadPageData() {
return new LivePagedListBuilder<>(new DataSource.Factory<Integer, MyData>() {
#Override
public DataSource<Integer, MyData> create() {
return new HBPagingDataSource<>((page, pageSize) -> loadPageSingle(page, pageSize));
}
}, 2).build();
}
the single
private SingleSubscribeProxy<Page<MyData>> loadPageSingle(int pageNum, int pageSize) {
return mModel.loadMyDates(pageNum, pageSize)
.doOnError(Throwable::printStackTrace)
.as(autoDisposable(this));
}
at fragment
mViewModel.page.observe(this, myDatas -> {
Timber.d("registerLiveData%s", myDatas.size());
myAdapter.submitList(myDatas);
});
Maybe related things:
I wrote subscribeOn and observeOn in retrofit's callAdapter
The viewModel is a scopeProvider since I'm using autoDispose
I tried some example in github. And it seems, the setValue for pageLivedata is always work after loadInitial. In this case, how can I use single?
It's seems solved.
The error is because schedule the thread using rxjava.
It makes single and datasource work in different thread.
In this case, callback onResult run after the observer.
So, I updated the callAdapter where I wrote subscribeOn and observeOn for single.
Filter by className when It's Page class, it won't do subscribeOn and observeOn.
Now the conclusion is, let paging handle the thread.
Related
I'm trying to replace AsyncTask with RxJava, since Async is deprecated in Android 11. however I cannnot get RxJava to work with Room,
This is currently working code with Asynctask:
In Repository:
public void insertItems(List<Items> items){
new insertItemsAsyncTask(PrjDao).execute(items);
}
private static class insertItemAsyncTask extends AsyncTask<List<Items>, Void, Void>{
private PrjDao prjDao;
private insertItemAsyncTask(PrjDao prjDao){
this.prjDao = prjDao;
}
#Override
protected Void doInBackground(List<Items>... lists) {
prjDao.insertItems(lists[0]);
return null;
}
}
in DAO
#Insert
void insertItems(List<Items> items);
I replaced repository code with:
public void insertItems(List<Items> items){
Completable.fromAction(() -> prjDao.insertItems(items)).subscribeOn(Schedulers.io()).observeOn(AndroidSchedulers.mainThread())
.subscribe(new CompletableObserver() {
#Override
public void onSubscribe(#NonNull Disposable d) {
}
#Override
public void onComplete() {
}
#Override
public void onError(#NonNull Throwable e) {
}
});
}
However It is not working, even though I managed to get Log output in onComplete.
Try:
DAO:
#Insert
Completable insertItems(List<Items> items);
Repository:
public void insertItems(List<Items> items){
prjDao.insertItems(items))
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(...);
}
Or better so:
Repository:
public Completable insertItems(List<Items> items){
return prjDao.insertItems(items))
}
And then, subscribe to the completable and handle subscribe callbacks where you actually call insertItems().
insertItems(items)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.subscribe(...);
In my opinion, repository should only provide bridge to the DB interface, and the caller should be the one to handle the subscribe callbacks, as each caller may want to handle the callbacks differently.
UPDATE
To use rxjava with room, please check that you have all needed dependencies in your build.gradle file:
implementation "androidx.room:room-runtime:[roomVersion]"
implementation "androidx.room:room-rxjava2:[roomVersion]"
annotationProcessor "androidx.room:room-compiler:[roomVersion]"
I currently use roomVersion 2.2.5
Here is a simple working demo of room + rxjava I just created, maybe you will find differences there:
https://github.com/phamtdat/RxRoomDemo
I'm using RxSearchView to emit out the results of a search query from an API to a recyclerview. However, if one of those query fails, onError() is called(which is expected) but the subscription as a whole is also canceled. Subsequent queries are not executed at all.
How should i modify the code so that the call to onError() is prevented when a query fails and the next incoming queries are executed normally?
Here's a code snippet:
subscription = RxSearchView.queryTextChanges(searchView)
.debounce(500, MILLISECONDS)
.filter(charSequence -> !TextUtils.isEmpty(charSequence))
.map(CharSequence::toString)
.subscribeOn(AndroidSchedulers.mainThread())
.observeOn(Schedulers.io())
.switchMap(query -> apiService.getSearchResults(query))
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber<SearchResponse>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(SearchResponse searchResponse) {
if (searchResponse.getStatus().equals("OK")) {
//update Adapter
} else {
//update error views
}
}
});
P.S: I am using switchMap() so that the results of old queries are ignored, if the results of new query has arrived.
You have to handle this error and return an object instead. You can do it, for example, by using onErrorResumeNext operator with apiService.getSearchResults(query) call. What you are going to return - depends on you, you can even return null if you want, but better to create some wrapper which can carry both response status flag and normal response if received.
Something like:
subscription = RxSearchView.queryTextChanges(searchView)
.debounce(500, MILLISECONDS)
.filter(charSequence -> !TextUtils.isEmpty(charSequence))
.map(CharSequence::toString)
.subscribeOn(AndroidSchedulers.mainThread())
.observeOn(Schedulers.io())
.switchMap(query -> apiService
.getSearchResults(query)
.onErrorResumeNext(error -> null)
)
.observeOn(AndroidSchedulers.mainThread())
.subscribe(new Subscriber<SearchResponse>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(SearchResponse searchResponse) {
if (searchResponse != null && searchResponse.getStatus().equals("OK")) {
//update Adapter
} else {
//update error views
}
}
});
Of course, this is naive example with using null, in reality you need to write error handling logic. Better to return wrapper, because if using RxJava 2, then it doesn't support null.
I'm trying to test a presenter that use RxJava to retrieve data from an interactor. In the setup method I'm doing something like:
#Before
public void setup() {
RxAndroidPlugins.getInstance().registerSchedulersHook(new RxAndroidSchedulersHook() {
#Override
public Scheduler getMainThreadScheduler() {
return Schedulers.immediate();
}
});
}
So in my test method I can test the presenter call:
#Test
public void testLoad() {
presenter.load();
verify(view).dataLoaded(data);
verify(interactor).load();
}
If I run the test with Android Studio everything work as expected, the issue is that If I try on command line
gradle test
Then the test fails because:
Actually, there were zero interactions with this mock.
So I've tried to put a Thread.sleep(2000) right after the call to the presenter and then it works, so I guess the Schedulers.immediate(); is not working from command line but I have no idea why and how to debug/fix. Do you have any idea?
EDIT: presenter implementation ->
public void load() {
Observable<List<Data>> obs = interactor.load()
.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io());
obs.subscribe(new Observer<List<Data>>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(List<Data> data) {
view.dataLoaded(data);
}
});
}
You can mock RxJava Schedulers as well.
RxJavaHooks.reset();
RxJavaHooks.setOnIOScheduler(scheduler -> Schedulers.immediate());
Typically a good thing to call reset on setup & teardown.
I am trying to test my ViewModel in my application, here is the constructor:
#Inject
public SearchUserViewModel(#Named("searchUser") UseCase searchUserUseCase) {
this.searchUserUseCase = searchUserUseCase;
}
In my test I create a SearchUserUseCase with mocks like this:
Observable error = Observable.error(new Throwable("Error"));
when(gitHubService.searchUser(MockFactory.TEST_USERNAME_ERROR)).thenReturn(error);
when(ObserverThread.getScheduler()).thenReturn(Schedulers.immediate());
when(SubscriberThread.getScheduler()).thenReturn(Schedulers.immediate());
searchUserUseCase = new SearchUserUseCase(gitHubService, SubscriberThread, ObserverThread);
In my ViewModel class I have this snippet which I want to test:
public void onClickSearch(View view) {
loadUsers();
}
private void loadUsers() {
if (username == null) {
fragmentListener.showMessage("Enter a username");
} else {
showProgressIndicator(true);
searchUserUseCase.execute(new SearchUserSubscriber(), username);
}
}
private final class SearchUserSubscriber extends DefaultSubscriber<SearchResponse> {
#Override
public void onCompleted() {
showProgressIndicator(false);
}
#Override
public void onError(Throwable e) {
showProgressIndicator(false);
fragmentListener.showMessage("Error loading users");
}
#Override
public void onNext(SearchResponse searchResponse) {
List<User> users = searchResponse.getUsers();
if (users.isEmpty()) {
fragmentListener.showMessage("No users found");
} else {
fragmentListener.addUsers(users);
}
}
}
Finally in my test I have this:
#Test
public void shouldDisplayErrorMessageIfErrorWhenLoadingUsers() {
SearchUserViewModel searchUserViewModel = new SearchUserViewModel(searchUserUseCase);
searchUserViewModel.setFragmentListener(mockFragmentListener);
searchUserViewModel.setUsername(MockFactory.TEST_USERNAME_ERROR);
searchUserViewModel.onClickSearch(view);
verify(mockFragmentListener).showMessage("Error loading users");
}
I get this error from Mockito:
Wanted but not invoked:
fragmentListener.showMessage(
"Error loading users"
);
I am not sure if this is a good test, but I somehow want to test the SearchUserSubscriber one way or another. Thanks
Edit: I have found similar questions to this problem here: Can't verify mock method call from RxJava Subscriber (which still isn't answered) and here: Verify interactions in rxjava subscribers. The latter question is similar but does not execute the subscriber in a separate class (which happens in SearchUserUseCase here).
I also tried RobolectricGradleTestRunner instead of MockitoJunitRunner and changed to Schedulers.io() and AndroidSchedulers.mainThread(), but I still get the same error.
Tried mocking SearchUserUseCase instead of GitHubService (which feels cleaner), but I'm not sure on how to test the subscriber that way since that is passed as an argument to the void method execute() in UseCase.
public void execute(Subscriber useCaseSubscriber, String query) {
subscription = buildUseCase(query)
.observeOn(postExecutionThread.getScheduler())
.subscribeOn(threadExecutor.getScheduler())
.subscribe(useCaseSubscriber);
}
And buildUseCase()
#Override
public Observable buildUseCase(String username) throws NullPointerException {
if (username == null) {
throw new NullPointerException("Query must not be null");
}
return getGitHubService().searchUser(username);
}
For me it worked out to add a Observable.Transformer<T, T> as followed:
void gatherData() {
service.doSomeMagic()
.compose(getSchedulerTransformer())
.subscribe(view::displayValue);
}
private <T> Observable.Transformer<T, T> getSchedulerTransformer() {
if (mTransformer == null) {
mTransformer = (Observable.Transformer<T, T>) observable -> observable.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread());
}
return mTransformer;
}
void setSchedulerTransformer(Observable.Transformer<Observable<?>, Observable<?>> transformer) {
mTransformer = transformer;
}
And to set the Transformer. I just passed this:
setSchedulerTransformer(observable -> {
if (observable instanceof Observable) {
Observable observable1 = (Observable) observable;
return observable1.subscribeOn(Schedulers.immediate())
.observeOn(Schedulers.immediate());
}
return null;
});
So just add a #Before method in your test and call presenter.setSchedulerTransformer and it should be able to test this. If you want more detail check this answer.
If you are using Mockito, you can probably get hold of a SearchUserSubscriber using an ArgumentCaptor, for example...
#Captor
private ArgumentCaptor<SearchUserSubscriber> subscriberCaptor;
private SearchUserSubscriber getSearchUserSubscriber() {
// TODO: ...set up the view model...
...
// Execute the code under test (making sure the line 'searchUserUseCase.execute(new SearchUserSubscriber(), username);' gets hit...)
viewModel.onClickSearch(view);
verify(searchUserUseCase).execute(subscriberCaptor.capture(), any(String.class));
return subscriberCaptor.getValue();
}
Now you can have test cases such as...
#Test
public void shouldDoSomethingWithTheSubscriber() {
SearchUserSubscriber subscriber = getSearchUserSubscriber();
...
}
I want to achieve that if i call the Obervable.subscribe(Action1) method, it does not throw OnErrorNotImplementedException anywhere, but if i call Obervable.subscribe(Action1, Action1), the second action is called when an error is raised as normal. I tried two ways:
.onErrorResumeNext(Observable.empty())
This way OnErrorNotImplementedException is not thrown, however if i pass also the second action, the action is never called either.
Second:
.lift(new Observable.Operator<T, T>() {
#Override
public Subscriber<? super T> call(Subscriber<? super T> subscriber) {
return new Subscriber<T>() {
#Override
public void onCompleted() {
if (!subscriber.isUnsubscribed()) {
subscriber.onCompleted();
}
}
#Override
public void onError(Throwable e) {
if (!subscriber.isUnsubscribed()) {
try {
subscriber.onError(e);
} catch (Throwable t) {
if (!(t instanceof OnErrorNotImplementedException)) {
throw t;
}
}
}
}
#Override
public void onNext(T t) {
if (!isUnsubscribed()) {
subscriber.onNext(t);
}
}
};
}
});
The problem with this if observeOn() is called later then this will be asynchronous and obviously my exception handling here will not work.
Is there way to achieve this. I wish there would be a subscribe() method which does not throw OnErrorNotImplementedException in onError.
Here is another possible solution, you can define the onNext and a Throwable (also you cannot loose the lambda syntax):
.subscribe(t -> doSomething(t), e -> showError(e));
here's how we do it at work. Instead of making actions we made an abstract NYTSubscriber which has onError and onCompleted implemented. This way you can use this subscriber and only implement the onNext callback OR you can override onError and onCompleted when necessary
public abstract class NYTSubscriber<T> extends Subscriber<T> {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
}
If you are using Kotlin then the syntax is like
.subscribe({success -> doOnSuccess(success)},{error -> doOnError(error)})
When you do like this '.onErrorResumeNext(Observable.empty())' your stream will be completed when error occurs - that's why your actions is never called.
You can user '.retry()' and your stream will be restarted automatically when you have an error.
This Error comes when calling the Subscribe method, but not providing onError() callbacks.
Kotlin
subscribe(object : DisposableCompletableObserver() {
override fun onComplete() {
// on successful completion }
override fun onError(e: Throwable) {
//error message
}
}
)