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EdHansberry
Kudo Collector
Kudo Collector

Force PowerApps to refresh images in a gallery?

I have a gallery that has an image in it, which is a URL to an external website (Azure Storage Blob actually). The gallery is used to upload new images to the storage blob.

If there is no image for an item, when I upload the image, refreshing the data source for the gallery forces the gallery to get the image.

 

However, if I replace an image, PowerApps will not show the new image in the gallery unless I close and restart the app. Is there a way to force it to refresh the image URLs? From an end user perspective, it looks like their image upload failed. I know the new image is available because refreshing a Power BI report (just refreshing the HTTP page, not refreshing the actual report contents) that is pulling these same images immediately shows the newly uploaded image.

Any ideas?

8 REPLIES 8
TiagoFreire
Kudo Kingpin
Kudo Kingpin

 

When you say "refresh", you mean a ClearCollect(), or an actual Refresh() and a ClearCollect()

 

At least according to the documentation, a Refresh() should tell the app to really look at the source, rather than cached data. 

datamaster
Resolver II
Resolver II

Did you try to reset the gallery?

 

 

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I don't mean a PowerApps refresh. I mean a web page refresh.

 

When there is no image, if a user uploads an image, a REFRESH(datasource) causes that gallery to show the image.

When there is an image, if a user uploads a new image, nothing I can find will cause PA to show the new image in the gallery. I've tried:

  • refreshing the data source
  • resetting the gallery
  • closing/restarting the app
  • refreshing the web page

 

Nothing works. All other uses for that newly uploaded image work fine. Normal web pages accessing that image URL, Power BI reports that show the image, etc. Those all work. PowerApps though won't do anything until it decides to expire its cache for that image, whenever that is.

I had similar problem a long time ago. I eventually traced it down to the fact that unless you literally find a way to change the URL in SQL, PowerApps will not recognize the change because SQL does have a concept of setting any flag such that PowerApps (and quite possibly your web browser) can check whether or not a file has been updated based on cache information stored in PowerApps at runtime.

I am doubtful there is any other way you can resolve this other then enforcing sort of change to the URL, the functionality of which you can implement in your app by appending a random 4 digit number to your file name each time you update that record in SQL. (Rand function).

If you have control of the way the images are served, can you add response headers that would tell the browser to not cache the image:

 

Cache-Control: no-cache, must-revalidate
Pragma: no-cache
Expires: Fri, 30 Oct 1998 14:19:41 GMT

 

(note the expiration date in the far away past)

 

And see if PowerApps honors them? 

 

If PowerApps is not honoring the expiration and cache control headers, that smells of a bug. 

 

Also, maybe the URL randomization startegy may be possible by means of a parameter: 

 

url="http://contoso.com/imagetobeserved.png?refresh=723687364"

Unfortunately the URL trick doesn't work. I tried adding a random string to the end using ?refresh=23987234 but that caused nothing to show up. 

 

I tried to give it another URL during editing too.

If(
    varShowFakeImage = true,
    "https://tineye.com/images/widgets/mona.jpg",
    "https://sitename.blob.core.windows.net/itemimages/" & ThisItem.ItemNumber & ".jpg?st=2019-11-22T18%3B16%3Z&se=2051-01-01T07%4D59%3A00Z&sp=rl&sv=MOREJIBBERISHHERE"
    )

During edit, it showed the mona.jpg, but once I pressed submit, refreshed the gallery, then turned varShowFakeImage to false, it returned the most recent image in the PowerApps cache. It did not go back and read what was in the storage blob.

 

Frustrated....

It isn't SQL. It is AzureStorageBlob, and I have no control over the URL it generates at that type of granularity. There is, as far as I can tell, no way for PowerApps to change it or imitate a change even through Flow Power Automate.

Anonymous
Not applicable

Hey, I had this problem today and believe I found a solution. Sorry to Necro but power apps can be such a pain and I hope this helps someone like myself. 

 

TLDR:

Refresh([@<THE NAME OF MY DATA CONNECTION>]);

Add that to some action that fetches your data. I made a dropdown menu's OnSelect do that command, and it fixed the issue in part. 

 

What was happening to me: 

I was designing an Employee Directory app for my company's Intranet site. I am doing this in PowerApps so that I can use the corresponding web part in SharePoint O365. I used a Vertical Gallery which fetches employee information from a SQL database to which I connected. I made a view from which to collect data as I needed to get it from several tables in the database (joined together myself).

On testing, loading in the employee pictures wasn't working—the pictures would use the cached values every now and then, causing the app to get pictures of different employees than for whom was queried. I realized I needed to somehow refresh the images and convince the dreaded App Blob to not use cached data. 

 

How I fixed it:

Added 

Refresh([@<THE NAME OF MY DATA CONNECTION>]);

To the OnSelect property of my dropdown.

I used OnChange to trigger a Filter action for the gallery when a new option was selected. Using that refresh line fixed one search completely, letting the images update as needed in my gallery after rigorous testing. 

 

However, another dropdown search I am using stores and uses whatever's in the cache. Adding refresh did not help. I am looking for any differences between the two and will post here when I figure out what is going on. Confident I'll have a final answer in the next post I make.

 

UPDATE:

Big success!!! That line works for my solution. Turns out, the failing record retrievals were due to those Employees having NULL values in place where photos did not exist. Relieved to see my issue concluded. Reply to this if you need any explanations on what I did / elaboration on what kind of app I built.

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