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EdHansberry
Level 8

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?

7 REPLIES 7
TiagoFreire
Level 8

Re: Force PowerApps to refresh images in a gallery?

 

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
Level 8

Re: Force PowerApps to refresh images in a gallery?

Did you try to reset the gallery?

 

 

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EdHansberry
Level 8

Re: Force PowerApps to refresh images in a gallery?

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.

Re: Force PowerApps to refresh images in a gallery?

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).
TiagoFreire
Level 8

Re: Force PowerApps to refresh images in a gallery?

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"

EdHansberry
Level 8

Re: Force PowerApps to refresh images in a gallery?

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....

Highlighted
EdHansberry
Level 8

Re: Force PowerApps to refresh images in a gallery?

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.

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