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WP7 / Silverlight]Binding remote images in listbox so the UI doesn't block

Answer 1

+1 A:

You could populate ImageLinks in a secondary thread that is not tied to the UI and bind it directly from the code-behind once it is populated instead of direct XAML binding.

Dennis Delimarsky 2010-09-21 17:06:23

Thanks for your suggestion i think i know what you mean (although ImageLinks is a List and ImageSource is a string). You want me to have maybe ImageSource as a BitmapImage instead of a string and populate it before i bind it to the Listbox. The problem with this is that i save the model with isolated storage witch won't let me have a property of type BitmapImage (Well i didn't mention this, sorry). I did think of something like this before, but ended downloading every image every time the view was navigated to.

Felipe Guajardo 2010-09-21 22:00:34

You can populate the `List` that you have in a separate thread. In fact, `ImageSource` can be bound via `SetBinding` like this: `ListBoxName.SetBinding(ListBox.ItemsSourceProperty, b);` where b is an instance of `Binding`.

Dennis Delimarsky 2010-09-21 22:32:26

Answer 2

+1 A:

You could also use the PersistentImageCache class from my Kawagoe toolkit, which has been designed precisely for this use case. Let me know if it helps! :)

Andréas Saudemont 2010-09-21 20:59:10

THanks. i don't know if i'm doing something wrong, but i was playing with the demo project from your toolkit in the WP7 emulator and when the application is first lauched, the UI locks for a few seconds while (i think) it's loading the very first items. After that i can smoothly scroll down a few items whose images have been downloaded, but as i reach again items with no images yet, the UI locks again. Of course if let the application load the whole collection, exit and reenter, all is good and smooth, BUT, all of this is exactly the behavior i get with the method i'm already using.

Felipe Guajardo 2010-09-21 22:11:13

The demo project uses the system image loader by default; it switches to PersistentImageCache once you tap the "persistent" button at the top of the page. It sounds like I could make things clearer here... :)

Andréas Saudemont 2010-09-22 12:18:50

I see. I'll give it another try.But i think you should use your toolkit by default because the demo may be a little biased since once one can switch, the images are already downloadloaded and your class could be just using the browser cache.

Felipe Guajardo 2010-09-22 14:12:37

Answer 3

+1 A:

Delay created a solution to exactly this problem.
See his blog entry on the topic at http://blogs.msdn.com/b/delay/archive/2010/09/02/keep-a-low-profile-lowprofileimageloader-helps-the-windows-phone-7-ui-thread-stay-responsive-by-loading-images-in-the-background.aspx

Matt Lacey 2010-09-22 09:57:14

Thanks, this worked better than i expected.

Felipe Guajardo 2010-09-22 15:32:06

One thing to note though. When i first tried the control, i added it to a xaml page with an associated sample data. As i replaced my <Image Source="{Binding Path=ImageSource}" /> with <Image delay:LowProfileImageLoader.UriSource="{Binding Path=ImageSource}" /> Visual Studio (2010 Express for Windows Phone from Sept. 16) crashed until i removed the xmlns referencing the sample data

Felipe Guajardo 2010-09-22 15:44:10

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WP7 / Silverlight]Binding remote images in listbox so the UI doesn't block

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