Loading indicator disappears randomly.

[hifall]

I found the loading indicator can disappear sometimes in such a scenario, but I have not found a consistent repro yet.

This happens in a table view with some chat messages.
1 fill the table view with about a dozen messages;
2 inert an image message whose image is managed by Kingfisher by calling:
imageView?.kf_showIndicatorWhenLoading = true
imageView?.kf_indicatorType = .Activity
imageView?.kf_setImageWithURL(...) with a placeholder image;
now the loading indicator shows up;
3 while the image is being loaded, scroll it out of the view port of the table, so that the image is not visible;
4 scroll the image back into the view port to make it visible; now the loading indicator could be missing even when the image is still being loaded.

[onevcat]

Will take a look at it soon.

[onevcat]

@hifall Hi,

After some investigation, I believe there is no issue in Kingfisher's loading indicator behaviors.

The issue you encountered might be related to the changes on collection view/table view in iOS 10. If you are calling Kingfisher's cancelDownloadTask in didEndDisplaying delegate method and resetting the image in collectionView(:cellForItemAt:), you may suffer from this. Since in iOS 10, Apple is using a more aggressive cache way on cells. Now they will not be in reuse queue at the time it goes out of screen, which means the resetting method in collectionView(:cellForItemAt:) may not be called. So the indicator will not show again.

You could try to put your set image code to collectionView(:willDisplay:forItemAt:) instead, to make sure the image is being reloaded and set correctly for that cell.

[onevcat]

You could find more about this change in iOS in session 219

[onevcat]

Some sample code added in #448 to show how to get performance benefit from iOS 10's prefetching cell and new cell life cycle.

[hifall]

Okay -- thanks for the heads-up. But the issue happened in iOS 9.3.5, instead of 10. Not sure enough at the moment what's going on, yet.

I will take a deeper look into this later.

[hifall]

So, I did try a few more times on iOS 9.3.5., and I saw the issue again. Although I did not dig through the source code to find the problem.

[pmusolino]

I have the same problem, before Xcode 8 and the transition to swift 2.3, the activity indicator worked properly on all my collectionViews. Now it doesn't work.

[onevcat]

@codeido I can not reproduce this issue on my environment (I tried both iOS 9 and 10).

Can you build a sample project for this? So I can dig into it deeper.

[pmusolino]

@onevcat you used swift 2.3?

[onevcat]

Yes, I tried swift2.3 branch and cannot reproduce it.

But I did find a bug which might stop you from setting the kf_showIndicatorWhenLoading to false, but it should not relate to this issue, if you are only setting it to true.

[pmusolino]

I fixed it on swift 2.3 and iOS 10 calling kf_showIndicatorWhenLoading=true before the method kf_setImageWithURL 👍 :|

[onevcat]

@codeido So may I know what's your original code? Maybe it could be improved.

[pmusolino]

Yeah @onevcat !

My original code was:

cell.imageProduct.kf_setImageWithURL(NSURL(string: variantSelected!.gallery![indexPath.item] ?? ""),
                                             placeholderImage: nil,
                                             optionsInfo: [.Transition(ImageTransition.Fade(0.5)), .ForceTransition])
cell.imageProduct.kf_showIndicatorWhenLoading = true

now is:

cell.imageProduct.kf_showIndicatorWhenLoading = true
cell.imageProduct.kf_setImageWithURL(NSURL(string: variantSelected!.gallery![indexPath.item] ?? ""),
                                             placeholderImage: nil,
                                             optionsInfo: [.Transition(ImageTransition.Fade(0.5)), .ForceTransition])

[hifall]

@codeido,

I don't see much difference between your code and what I posted at top, except that you pass in non-nil optionsInfo. I tried yours, but the problem stays.

[hifall]

@onevcat,

Regarding your comment: "But I did find a bug which might stop you from setting the kf_showIndicatorWhenLoading to false, but it should not relate to this issue, if you are only setting it to true.", this is what it's like in our scenario: we have 2 types of images managed using Kingfisher, one that displays a loading indicator when the image is being loaded, and the other one that displays NO loading indicator. So indeed, kf_showIndicatorWhenLoading can be set to false in our case -- could that cause the images that are supposed to display a loading indicator to actually fail to do so?

[hifall]

@onevcat,

This issue happens around 50% chance on my device. So once you have a fix for the kf_showIndicatorWhenLoading issue you mentioned, maybe I can give it a test here.

[onevcat]

@codeido That's true, you need to set the loading indicator before you begin loading an image.

@hifall I pushed a commit for it in swift2.3 branch. Would you like to give it a try?

[hifall]

@onevcat,

I am not seeing any new commit from last few hours in swift2.3 branch. Am I missing something here?

[onevcat]

It should be there.

c20e455

I made the change earlier, just didn't push it until now.

[hifall]

Thanks @onevcat.

I have tested your fix. But the problem still shows.

[onevcat]

@hifall Ummm, checked the code again and not sure about why.

Are you trying to set the indicator and/or image in another thread instead of main thread?

[onevcat]

Or if there is a demo could reproduce it, I'd like to dig it deeper. Currently I cannot reproduce it so it's quite hard to debug.

[onevcat]

@hifall Hi, any progress for this?

[hifall]

@onevcat,

I have not been able to find time to isolate this issue in a reasonably small project. I will get back to you when I can.