Wikidata items repeated in Explore

[nicolas-raoul]

1. Go to Explore
2. Type "apple"
3. Tap "Items"
4. Scroll
5. Notice that some items appear several times, for instance "apple cultivar"

[vanshikaarora]

@nicolas-raoul I noticed that only some values are repeated and not all of them. I used breakpoints and checked for the offset value while calling the APIs. They seem to be perfect. I am not sure, but it might be an issue with the API

[nicolas-raoul]

can you please output all thumbnail urls to logcat?

…

On Sat, 24 Aug 2019, 17:54 Vanshika Arora, ***@***.***> wrote: @nicolas-raoul <https://github.com/nicolas-raoul> I noticed that only some values are repeated and not all of them. I used breakpoints and checked for the offset value while calling the APIs. They seem to be perfect. I am not sure, but it might be an issue with the API — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#3137?email_source=notifications&email_token=AAAYKBX7J7SLIUGEWXAW363QGDZL3A5CNFSM4IOUYXPKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD5B4ACI#issuecomment-524533769>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAYKBXUCWVH55BHSYQM763QGDZL3ANCNFSM4IOUYXPA> .

[vanshikaarora]

okay

[ruizha]

May I be assigned this issue?

[nicolas-raoul]

@Rui-Zhang1997 Yes, thank you, and sorry for the late reply! Please let us know about your progress :-)

[nicolas-raoul]

@Rui-Zhang1997 Are you still working on this? Feel free to post any findings or code, even if incomplete :-)

[nicolas-raoul]

Still happening.

[vvijayalakshmi21]

Hi @nicolas-raoul I checked this and I believe after the second set of 25 items are fetched, they're simply repeating. From the attached screenshots we can see that after pyrus item the first item of the second 25 fetched is displayed and the list continues. This keeps happening upon scrolling further down.
A couple of reasons I could think of for this issue are:

1. We're not properly requesting the next page
2. Not updating the UI even though the data fetched from the server are right.

I will debug further and share my analysis here

[vvijayalakshmi21]

This shows the last item displayed from the first call. (British Rock band)

This shows the first few items of the second 25 call.

This shows the last item in the second 25 call. (Pyrus)

Then the first item of the second call repeats followed by the entire list.

[vvijayalakshmi21]

If we slow-scroll down the items OR debug the code, the issue does not occur. The item list is properly updated without repetitions. It is only when the user keeps scrolling down the items while a call to the server is yet to finish, we see the issue.
The below code snippet gets executed more times than once when the user scrolls down faster resulting in the list being displayed with repeated items.

[vvijayalakshmi21]

On further analysis I can see that when a user scrolls down faster, the firstVisibleItemPosition and visibleItemCount variables change rapidly and in a way that the above if condition is satisfied. Please find attached the variable values when we slow-scroll or Debug and fast-scroll the items.
We can clearly see that we are making more than one call with the same offset value 25.

fast scroll.txt
slow scroll.txt