Comments on: iPhone development – Downloading an image asynchronously

By: Greg Maletic

Greg Maletic — Thu, 10 Dec 2009 01:43:24 +0000

>Downloading an image, or anything else for that matter, asynchronously from the web requires the use of a NSURLRequest and NSURLConnection.

Why do you say this? Why can’t you just wrap [NSData dataWithContentsOfURL:] in an NSOperation and implement your own callback? Is there a reason why that is a bad idea?

Thanks.

By: Teerasej

Teerasej — Thu, 08 Oct 2009 05:35:37 +0000

Thank you for this article. Your writing is very good and easy understand. I think this is the best one.

By: Franck

Franck — Mon, 23 Feb 2009 20:15:22 +0000

Hi Björn, nice article!

Like Eric, I’m wondering about the way to use your class with many images?

Your idea consisted in adding a property refering to the destination UIImage but how would you use it ?

Thanks a lot for your answer.

Cheers,
–Franck

By: blogg

blogg — Wed, 11 Feb 2009 23:26:32 +0000

Very nice information. Thanks for this.

By: Björn Sållarp

Björn Sållarp — Mon, 01 Dec 2008 20:35:02 +0000

Hi Eric!

I’m glad you like the class. Be sure you’ve checked out the revised class here: http://blog.sallarp.com/2008/11/asynch-uiimage-revisited/

The new intenetimage class is much more stable. You can solve your problem in a number of ways. The easiest is to just add a property on the InternetImage class that can work as an identifier. Another neat way to solve it would be to add a pointer (id) property on the InternetImage that you set to the UIImage (or whatever) you wish to set the image to once it’s been downloaded.

Happy coding!
// Björn Sållarp

By: Eric

Eric — Sun, 30 Nov 2008 01:37:57 +0000

Hi,
Thanks for the internetimage class. It is good for downloading a single image.
How to use the internetimage class to download 3 images one by one (not need in sequence at all). It seems the delegate cannot identify which image it is downloading.

By: iPhone - Downloading an image asynchronously. Revisited!

iPhone - Downloading an image asynchronously. Revisited! — Sat, 01 Nov 2008 23:28:43 +0000

[...] – Downloading an image asynchronously. Revisited! Nov.02, 2008 in Uncategorized, iPhone In a previous post I wrote about downloading an image asynchronously. As my work has progressed with my app (which is [...]

By: Josh

Josh — Mon, 13 Oct 2008 07:31:54 +0000

OK, thank you.

By: Björn Sållarp

Björn Sållarp — Mon, 13 Oct 2008 04:41:18 +0000

Hi Josh! The iPhone supports PNG, TIFF, JPEG, GIF, BMP, CUR and XBM image formats. The dev docs strongly recommend PNG over the other formate. But of course you can download other types than images. The concept is the same for any file you download, but store the data in the file system instead of inserting it into an image.
I haven’t worked with storing files on the phone but you can find documentation on the file system on iPhone dev center here: http://developer.apple.com/iphone/library/documentation/Cocoa/Conceptual/LowLevelFileMgmt/LowLevelFileMgmt.html

Good luck!

By: Josh

Josh — Mon, 13 Oct 2008 01:38:19 +0000

Hi, thanks for the tutorial. How do I save this downloaded image to the memory of the phone? also, how would I save it if it was another file type? Thanks again.