@NonNull
public Observable<PageResult<T>> load(
@NonNull DataConverter<T> dataConverter,
@NonNull DatabaseQuery databaseQuery,
@NonNull Observable<Page> pageObservable) {
final SparseArrayCompat<T> allItems = new SparseArrayCompat<>();
final Observable<Cursor> cursorObservable =
database.load(databaseQuery).doOnNext(cursor -> allItems.clear());
return Observable.combineLatest(
pageObservable,
cursorObservable,
(page, cursor) -> {
final List<T> pageItems = new ArrayList<>();
for (int i = page.getStart(),
size = Math.min(cursor.getCount(), page.getStart() + page.getSize());
i < size;
i++) {
T item = allItems.get(i);
if (item == null) {
cursor.moveToPosition(i);
item = dataConverter.from(cursor);
allItems.put(i, item);
}
pageItems.add(item);
}
return new PageResult<>(cursor, allItems, pageItems, page);
});
}
