iOS - Thread and alertiview

i've an app that when start control updates and other things. If the app find some updates they will ask user if this updates have to be done. If user select YES i want that a spinner appear on main screen until update finish. But when i tap YES my alert view doesn't disappear and remain on screen until update is finished. Is it possible to create a thread that run on the main thread and stop when update in finished? Thanks

-(void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex {

    if (buttonIndex==1) {
        [self showActivityViewer];
        [self downloadControlAndUpdatePoi];
        [self downloadCont开发者_如何转开发rolAndUpdateItinerari];
        [self downloadControlAndUpdateArtisti];
        [self downloadControlAndUpdateEventi];
        [self hideActivityViewer];
        NSLog(@"AGGIORNA");
    } else {
        NSLog(@"NON AGGIORNARE");
        return;
    }
}

If the methods

    [self downloadControlAndUpdatePoi];
    [self downloadControlAndUpdateItinerari];
    [self downloadControlAndUpdateArtisti];
    [self downloadControlAndUpdateEventi];

are executed synchronously (that means that they return only after having processed completely), so:

     [self hideActivityViewer];

is executed only at the very end.

A simple approach to this is scheduling the execution of your methods on the main thread:

 [self performSelector:@selector(downloadControlAndUpdatePoi) withObject:nil afterDelay:0];
 ....
 [self hideActivityViewer];

so that those methods are executed only after control has returned to the main loop and the UI has been updated.

Otherwise, you could use:

+ detachNewThreadSelector:toTarget:withObject:

from NSThread, to do more or less the same. In this case I would suggest creating a wrapper method for all of your dowloadAndUpdate... methods, but keep in mind that you can't update the UI from a secondary thread.

In both cases, you should take some care about synchronizing the download... operations with the rest of your workflow after removing the alert view.