iOS And XML Image Results Download in the Background?

[John Patten]

Hi All...

I've tried both Ken and Gerry's suggestions for downloading images in the background via a URL.

In Ken's example, I was able to get the an images downloaded to a img object, however when navigating to another card LiveCode started behaving strangely and it would lock up for a minute, or two, and then proceed to give me an assortment of URL Errors about exceeding the 4000 limit etc., etc. ending with a ForceQuit. 

In Gerry's example I managed to download a single image to a folder, but could not loop through my list of image URLs in order to download each one.

I attempted to combine both Ken and Gerry's examples, in order to prevent the error messages I was receiving in Ken's first example. However, it is not working...yet.

Here is what I have:

on mouseUp
   send "downloadImage 1" to me in 0 milliseconds
end mouseUp



on downloadImage idx
if idx <= the number of lines in cd fld "imageURLs" then
set the itemDel to tab
   put item 1 of line idx of cd fld "imageURLs" into tURL
   set the itemDel to "/"
   put the last item of tURL into tImagename
   libUrlDownloadToFile tURL, specialfolderpath ("Documents") & "/WhaleImages/" & tImagename
   send "downloadImage "&(idx+1) to me in 0 milliseconds
   end if

end downloadImage

Any suggestions welcome...

Thank you!

John Patten
SUSD


On Feb 21, 2012, at 4:20 AM, Ken Corey wrote:

> Sure, why not?  Let's assume that this is all kicked off from a button press:
> 
> -- I assume you have your URLs in a list
> 
> on mouseUp
>  -- send in 0 milliseconds means call downloadImage as soon
>  --   as this handler is done
>  -- I'd create placeholder graphics where the images might
>  --   go once downloaded, and then you can put them into a list
>  send "downloadImage 1" to me in 0 milliseconds
> end openCard
> 
> on downloadImage idx
>  -- check to see if we've fallen off the end of the list.
>  if idx <= the number of lines of listOfURLs then
>    get URL "http://blah.com/image.gif"
>    -- do something terribly clever to display them to the user.
>    -- e.g. replace the placeholder images above for item idx
>    --
>    -- queue up the next image for download
>    send "downloadImage "&(idx+1) to me in 0 milliseconds
>  end if
> end downloadImage
> 
> So, your app interface should be happily trundling along responding to user input, while the images are being downloaded.  Increase the '0 milliseconds' for more responsiveness.
> 
> This assumes you want the images to come down one at a time.  You /could/ queue up more than one at a time by sending 'downloadImage' to yourself multiple times, but then you'd have to get fancier managing the index.
> 
> You probably don't want to issue all the sends at the same time, because unless you have a monster fat pipe none of them will come down at any rational rate of speed.
> 
> You might also want to think about caching the image somehow.  Check for its existance before the get, and avoid hitting the net at all. (Of course, that means you have to let the user clear the cache, limit the size to which it grows, etc.)
> 
> -Ken
> 
> 
> 
> On 19/02/2012 05:40, johnpatten at me.com wrote:
>> I'm looking to use the Flickr API search routine to return the latest
>> images for a specific tag. I will probably limit it to the 10 or 20 most
>> recent images. I can create the resulting URL to the images from the
>> resulting XML, and set the file name of an image to that URL, looping
>> through the list of images, but I'm curious as to what would be best
>> practice would be to download these images in the background? Ideally I
>> would like the user to be able to use the simulated swipe routines
>> between the images.
>> 
>> The only thing I can think of is downloading the images in the
>> background as soon as the iOS app is launched. Could a script like this
>> be launched at openStack and run in the background?
> 
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