The iOS app UI snapshot is not updated when the Background task completes about ios-samples

[rzaitov]

I think you are interested in SimpleBackgroundTransfer sample:
https://github.com/xamarin/monotouch-samples/tree/master/SimpleBackgroundTransfer

Here the prof that iOS takes snapshot after completionHandler invocation. Paste the following code
InvokeOnMainThread (() => {
var v = new UIView ();
v.BackgroundColor = UIColor.Red;
v.Frame = new CoreGraphics.CGRect (0, 0, 100, 100);
appDelegate.Window.AddSubview (v);
v.Center = appDelegate.Window.Center;
});

just before the handler invocation:
https://github.com/xamarin/monotouch-samples/blob/bd9cefdd3e6eb028b65ab0be2a47ac6268e9e569/SimpleBackgroundTransfer/SimpleBackgroundTransfer/SimpleBackgroundTransferViewController.cs#L151

This will put red rectangle to window's hierarchy, then iOS will take snapshot, so you should be able to see red square in app switcher. Steps to reproduce:

• paste code before handler();
• run app
• press "Start"
• press Home button and wait
• go to app switcher

[AlexBrownShi]

Well, that is how I was doing it originally and it works great. But it appears AirWatch app wrapping does not support creating your own NSURLSession with configuration (you must use SharedSession) so, I am now back to using the ModernHttpClient for the upload and using this older method of running a background task as in the BackgroundExecution example (which seems to work with airwatch). One of the downsides is that it doesn't seem to give me a snapshot of the app when the task completes.

Any ideas?

I suppose if I could modify or re-initialize the SharedSession to make it run with backgrounding delegate, that might solve my problem as well.

[rzaitov]

I am afraid that these are the only possible ways:
http://developer.xamarin.com/guides/ios/application_fundamentals/backgrounding/part_3_ios_backgrounding_techniques/updating_an_application_in_the_background/

[AlexBrownShi]

What do you mean? Are you saying that the BackgroundExecution example method is no longer supported by Xamarin/iOS (I noticed the documentation was taken down off the site recently) or that it just doesn't update the app screen snapshot when completed?

[rzaitov]

Just to clarify we support all samples in this repo.
Looks like I wasn't clear in my previous comment, let me explain. As I understand you want to update UI while app in the background mode. The possible solutions are explained here:
http://developer.xamarin.com/guides/ios/application_fundamentals/backgrounding/part_3_ios_backgrounding_techniques/updating_an_application_in_the_background/

And I am afraid that there is no other way to update your UI while your app is working in background mode. But I am not 100% sure.

[AlexBrownShi]

The method of background execution outlined in the BackgroundExecution example is no longer documented on this page - it used to be as recent as a couple of months ago. The code still works - but doesn't update that UI snapshot. I mean updates to the UI still seem to execute, they just don't update the screenshot and are visible only when you switch back to the app.

Does that make sense? I want to make sure you understand the problem, but it sounds like you are saying that it is just not supported in that situation.

[rolfbjarne]

@AlexBrownShi were you ever able to figure out a solution to your problem? Or do you still need help?

[spouliot]

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