[Bug]: Attempt to read from null error in Explore -> Map fragment

[kanahia1]

Summary

This issue is caused when there are no elements in mediaList Maybe the issue caused when there are no media (images) available at specific coordinate.

Steps to reproduce

1. Open Explore -> Map Fragment in App
2. Go to Bihta, Patna, India or Coordinates = 25.5303740, 84.8597150 in map

Expected behaviour

Place's images should appear on the map.

Actual behaviour

Toast message Error fetching nearby places. Attempt to read from null...

Device name

Samsung S21

Android version

Android 14

Commons app version

4.2.1-debug-HEAD~9be8df3

Device logs

java.lang.NullPointerException: Attempt to read from null array at fr.free.nrw.commons.explore.map.ExploreMapPresenter.getLatLngBounds(ExploreMapPresenter.java:223) at fr.free.nrw.commons.explore.map.ExploreMapPresenter.updateMapMarkers(ExploreMapPresenter.java:193) at fr.free.nrw.commons.explore.map.ExploreMapFragment.updateMapMarkers(ExploreMapFragment.java:433) at fr.free.nrw.commons.explore.map.ExploreMapFragment.lambda$populatePlaces$5$fr-free-nrw-commons-explore-map-ExploreMapFragment(ExploreMapFragment.java:413)

Screen-shots

WhatsApp.Video.2024-01-19.at.12.32.38_ef292d87.mp4

Would you like to work on the issue?

Yes

[ShashwatKedia]

@kanahia1 this might happen because you are using the betaDebug variant, as was the case here #5255 (comment), pointed out by @nicolas-raoul here: #5255 (comment). Does the issue persist in prodDebug variant as well?

[kanahia1]

Thanks @ShashwatKedia it worked! on production server. But we will need to handle it since there can be a place on earth where are no images in that case there will be this error. So, we can show some dialog at that place to make user experience better.

[nicolas-raoul]

Indeed, I just tried with prodDebug in Siberia and get the same error:

[rohit9625]

Using dialogues can be interrupting for users. Instead, we should use Snackbars with proper error messages. Concisely, this is what I mean :

Although, we can move from Toasts to Snackbars. What do you say?
@nicolas-raoul @kanahia1

[nicolas-raoul]

Yes snackbar is good.

I think we should try to convey the real problem to the user, though.

Here, the real problem is that there are no Wikidata items in that area, right?

[rohit9625]

No problem, I am adding a new string in the resource. This will be displayed to the user.
Can you provide a well-formatted message to be displayed to the user?

[nicolas-raoul]

How about No Wikidata items in this area? :-)

[rohit9625]

Well, this seems to be a good response we can provide. I am placing it in the resources.
Although, I have a question, i.e., I created a method to display the snackbar in the same file where showToasts() method is defined.
Do I need to create any UI test for snackbar?

[rohit9625]

After making changes, these are the results:

Light Mode

Dark Mode

However, there was a resource already string like this:
<string name="no_nearby_places_around">No nearby places around</string>
But the text provided by you seems much better.

[nicolas-raoul]

Ah, no_nearby_places_around is great, thanks for finding it! 🙂

[nicolas-raoul]

Ah wait, I was totally forgetting the context since yesterday, I am so sorry! 😱

Please use "No pictures in this area".

Thanks! 🙂

[rohit9625]

Done 👍

Please express your thoughts about the colors and action button for the **Snackbars** because I am considering replacing all the toasts with a beautiful **Snackbar**.
What do you think?

[kanahia1]

Hey @rohit9625,
I think we cannot replace all the Toasts with Snackbars since Toasts usually are used to display text related with system or some background services since Toasts are shown even if Activity is finished. So replacing all the Toasts with SnackBars can cause disturbance in User Experience.

---

References
https://m2.material.io/components/snackbars#usage
https://stackoverflow.com/questions/34432339/android-snackbar-vs-toast-usage-and-difference

[rohit9625]

Oh, my bad!😅
Yeah, you are right Mr. @kanahia1. We can't replace all the toasts but some toasts should be replaced I guess.

[nicolas-raoul]

@rohit9625 Your screenshot looks great! 🙂

[kanahia1]

Hey @rohit9625, I have added TODO for snackbar in #5475, you can add code for snackbar and share a pull request. 🙌

[rohit9625]

Okay I'll do it :)

[rohit9625]

Showing response message will work after solving this issue #5487
Have a look @kanahia1

[kanahia1]

Sure @rohit9625 I will look into #5487

[rohit9625]

Done Mr. @kanahia1 👍

[rohit9625]

Hello @nicolas-raoul
Can you please look at the PR that solves this issue?
I don't know why the previous PR closed. I am creating a new PR.