Re: Updating progress of UIProgressView. And Getting Better Saving Performance
Re: Updating progress of UIProgressView. And Getting Better Saving Performance
- Subject: Re: Updating progress of UIProgressView. And Getting Better Saving Performance
- From: Laurent Daudelin <email@hidden>
- Date: Mon, 6 Dec 2010 18:21:45 -0800
On Dec 6, 2010, at 17:16, email@hidden wrote:
> On Dec 6, 2010, at 5:37 PM, Gustavo Pizano wrote:
>
>> Hello.
>>
>> My application is saving some data, and it takes a while to do it, it can be 1 second to 10 sec around.. Im doing some image processing, The thing is..
>>
>> I send the saving operation in another thread using the NSThread + detachNewThreadSelector:toTarget:withObject: method, and in the main thread I update a UIActivityIndicator, and stop it when I receive the NSThreadWillExitNotification. The problem is that when it takes long to save, it may seem the app is somehow stuck, even the spinning indicator is running. I wanted to change the ActivityIndicator to a progressview, but then I can't make it work because the saving process not on the main thread, i think.. correct me if Im wrong, Im not so much familiar with multithreaded apps.
>>
>> As for the saving process, what I do is the following.
>>
>> I have a Parent view which contains subviews, these subviews are drawing images. The user can modify this images, (scale and rotate), so when I save i encode these views so it will save the view's transform, and then I archive the data I encoded for all these subviews.
>
>
> <your code deleted>
>
> You are correct that you cannot call GUI methods from other threads, but NSObject (which all your UI objects inherit from) has the method.
>
> - (void)performSelectorInBackground:(SEL)aSelector withObject:(id)arg
>
> So from your other thread, you can update the progress indicator by using it to call a method that updates the progress.
>
>
> This is even easier if you are targeting iOS 4.0 and higher using Blocks and GrandCentral Dispatch.
>
> Code typed in email (i.e., not tested):
>
> dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
> // code you want implemented on another thread goes here:
>
> dispatch_async(dispatch_get_main_queue(), ^{
> // code executed on main thread goes here (i.e., updating the progress indicator in your case
>
> });
> });
>
> HTH,
> Dave
Maybe I'm missing something but aren't the UI actions supposed to happen in the main thread, in this case, he should really call "performSelectorOnMainThread:withObject:waitUntilDone:"?
-Laurent.
--
Laurent Daudelin
AIM/iChat/Skype:LaurentDaudelin http://www.nemesys-soft.com/
Logiciels Nemesys Software email@hidden
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