Paging Library for those which don't have any numeric Id - android

I am actually consuming Triposo's API to show the list of countries. https://www.triposo.com/api/
However, in responses, there is no numeric Id and I am struggling while incrementing page size. What should I perform on such responses to overcome? For instance, Github API is fully suitable for Paging Library since it returns itemId as numeric.
https://api.github.com/users
Example Response
{
"results": [
{
"name": "Benin",
"country_id": "Benin",
"snippet": "A safe and relatively easy country for travellers to visit; birthplace of the Voodoo religion and former home of the Kingdom of Dahomey.",
"parent_id": null,
"score": 3.98127216481287,
"id": "Benin"
}
],
"estimated_total": 30845,
"more": true
}
ItemKeyedDataSource.java
public class ItemKeyedCountryDataSource extends ItemKeyedDataSource<Integer, CountryResult> {
private EndpointHelper endpointHelper;
ItemKeyedCountryDataSource() {
endpointHelper = EndpointHelper.getInstance();
}
#Override
public void loadInitial(#NonNull LoadInitialParams<Integer> params, #NonNull final LoadInitialCallback<CountryResult> callback) {
final List<CountryResult> countryResultList = new ArrayList<>();
endpointHelper.getCountryList(0)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.retry(1)
.onErrorResumeNext(new Func1<Throwable, Observable<? extends CountryWrapper>>() {
#Override
public Observable<? extends CountryWrapper> call(Throwable throwable) {
return Observable.error(throwable);
}
})
.subscribe(new Subscriber<CountryWrapper>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(CountryWrapper countryWrapper) {
if (countryWrapper.getResults().size() > 0) {
countryResultList.addAll(countryWrapper.getResults());
callback.onResult(countryResultList);
}
}
});
}
#Override
public void loadAfter(#NonNull LoadParams<Integer> params, #NonNull final LoadCallback<CountryResult> callback) {
final List<CountryResult> countryResultList = new ArrayList<>();
endpointHelper.getCountryList(params.requestedLoadSize)
.subscribeOn(Schedulers.io())
.observeOn(AndroidSchedulers.mainThread())
.retry(1)
.onErrorResumeNext(new Func1<Throwable, Observable<? extends CountryWrapper>>() {
#Override
public Observable<? extends CountryWrapper> call(Throwable throwable) {
return Observable.error(throwable);
}
})
.subscribe(new Subscriber<CountryWrapper>() {
#Override
public void onCompleted() {
}
#Override
public void onError(Throwable e) {
}
#Override
public void onNext(CountryWrapper countryWrapper) {
if (countryWrapper.getResults().size() > 0) {
countryResultList.addAll(countryWrapper.getResults());
callback.onResult(countryResultList);
}
}
});
}
#Override
public void loadBefore(#NonNull LoadParams<Integer> params, #NonNull LoadCallback<CountryResult> callback) {
//Do nothing
}
#NonNull
#Override
public Integer getKey(#NonNull CountryResult item) {
return ?; // what do I return here?
}
}
ViewModel.java
public class SearchableActivityViewModel extends ViewModel {
private LiveData<PagedList<CountryResult>> countryResult;
SearchableActivityViewModel() {
Executor executor = Executors.newFixedThreadPool(5);
CountryResultDataSourceFactory countryResultDataSourceFactory = new CountryResultDataSourceFactory();
PagedList.Config config = new PagedList.Config.Builder()
.setEnablePlaceholders(false)
.setInitialLoadSizeHint(20) //first load
.setPageSize(21)
.build();
//noinspection unchecked
countryResult = new LivePagedListBuilder<String, CountryResult>(countryResultDataSourceFactory, config)
.setFetchExecutor(executor)
.build();
}
public LiveData<PagedList<CountryResult>> getCountryResult(){
return countryResult;
}
#Override
protected void onCleared() {
super.onCleared();
}
}
Thanks in advance. Hope I am clear.
Best,

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Here is what I came up with:
RxUtils.createEditTextChangeObservable(txtInput)
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public Pair<String, List<Stop>> call(List<Stop> stops) {
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#Override
public Observable<List<Stop>> call(Pair<String, List<Stop>> queryAndStops) {
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.map(new Func1<LocationNameResponse, List<Stop>>() {
#Override
public List<Stop> call(LocationNameResponse locationNameResponse) {
// since there was no if-else in your original code (you were always
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#Override
public void call(Throwable throwable) {
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where:
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public static final Func1<String, Boolean> STRING_IS_NOT_EMPTY = new Func1<String, Boolean>() {
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So, this at least removes the need to return Observable.just(null) and then check for that down the chain.

You can move your second concatMap to the only place you need it - after combineLatest
RxUtils.createEditTextChangeObservable(txtInput)
.throttleLast(200, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread())
.concatMap(new Func1<EditText, Observable<Pair<String, List<Stop>>>>() {
#Override
public Observable<Pair<String, List<Stop>>> call(EditText editText) {
String query = editText.getText().toString();
//searchStopResultFragment.setLastQuery(query);
if (query.isEmpty()) {
return Observable.just(null);
}
return Observable
.combineLatest(StopProvider.getStopResultObservable(getContentResolver(), query), Observable.just(query), new Func2<List<Stop>, String, Pair<String, List<Stop>>>() {
#Override
public Pair<String, List<Stop>> call(List<Stop> stops, String s) {
return new Pair(s, stops);
}
})
.concatMap(new Func1<R, Observable<? extends Pair<String, List<Stop>>>>() {
#Override
public Observable<? extends Pair<String, List<Stop>>> call(R r) {
if (queryAndStops.second.size() == 0) {
return RestClient.service().locationName(queryAndStops.first).concatMap(new Func1<LocationNameResponse, Observable<? extends List<Stop>>>() {
#Override
public Observable<? extends List<Stop>> call(LocationNameResponse locationNameResponse) {
return Observable.just(locationNameResponse.getAddresses());
}
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} else {
return Observable.just(queryAndStops.second);
}
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});
}
})
.subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread()).compose(this.<List<Stop>>bindToLifecycle())
.subscribe(new Action1<List<Stop>>() {
#Override
public void call(List<Stop> stops) {
if (stops != null) {
searchStopResultFragment.showStops(stops);
} else {
searchStopResultFragment.showStartItems();
}
}
}, new Action1<Throwable>() {
#Override
public void call(Throwable throwable) {
showError(throwable);
}
});

Solved it using concatmap and combine latest:
RxUtils.createEditTextChangeObservable(txtInput).throttleLast(200, TimeUnit.MILLISECONDS, AndroidSchedulers.mainThread()).concatMap(new Func1<EditText, Observable<Pair<String,List<Stop>>>>() {
#Override
public Observable<Pair<String, List<Stop>>> call(EditText editText) {
String query = editText.getText().toString();
//searchStopResultFragment.setLastQuery(query);
if(query.isEmpty()){
return Observable.just(null);
}
return Observable.combineLatest(StopProvider.getStopResultObservable(getContentResolver(), query), Observable.just(query), new Func2<List<Stop>, String, Pair<String, List<Stop>>>() {
#Override
public Pair<String, List<Stop>> call(List<Stop> stops, String s) {
return new Pair(s,stops);
}
});
}
}).concatMap(new Func1<Pair<String, List<Stop>>, Observable<List<Stop>>>() {
#Override
public Observable<List<Stop>> call(Pair<String, List<Stop>> queryAndStops) {
if(queryAndStops!=null) {
if (queryAndStops.second.size() == 0) {
return RestClient.service().locationName(queryAndStops.first).concatMap(new Func1<LocationNameResponse, Observable<? extends List<Stop>>>() {
#Override
public Observable<? extends List<Stop>> call(LocationNameResponse locationNameResponse) {
return Observable.just(locationNameResponse.getAddresses());
}
});
} else {
return Observable.just(queryAndStops.second);
}
}
return Observable.just(null);
}
}).subscribeOn(Schedulers.newThread())
.observeOn(AndroidSchedulers.mainThread()).compose(this.<List<Stop>>bindToLifecycle()).subscribe(new Action1<List<Stop>>() {
#Override
public void call(List<Stop> stops) {
if (stops != null) {
searchStopResultFragment.showStops(stops);
}else{
searchStopResultFragment.showStartItems();
}
}
}, new Action1<Throwable>() {
#Override
public void call(Throwable throwable) {
showError(throwable);
}
});
However is there some nicer way to break out of the chain without sending Observable.just(null) and check for nulls in next call?

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