Layer appearing with a delay - iphone

Question

I have an iPhone game in which players can tweet their score.
I use TWTweetComposeViewController for this.
Since the Twitter sheet can take some time to load, I would like a "loading..." layer to show up after the player has clicked the tweet button, while waiting for the Twitter sheet to show up.
My problem is that the layer (named "colcol" in the code below) only shows up once the tweet sheet is ready! It's as if the layer waited for the tweet sheet to be ready to show up. Which is definitely not what I expect.
Any idea why ?
Thank you!
Here is the tweetScore function, called when the user touches a CCMenuItemImage:
- (void) tweetScore: (CCMenuItem *) menuItem {
colcol=[CCLayerColor layerWithColor:ccc4(0,0, 0, 200) width:50 height:50];
colcol.position=ccp(winSize.width/2-25,winSize.height/2-25);
[self addChild:colcol z:15];
if ([TWTweetComposeViewController canSendTweet])
{
TWTweetComposeViewController *tweetSheet = [[TWTweetComposeViewController alloc] init];
[tweetSheet setInitialText:[NSString stringWithFormat:#"I scored %d!", playerScore]];
tweetSheet.completionHandler = ^(TWTweetComposeViewControllerResult result) {
[appDelegate.viewController dismissModalViewControllerAnimated:YES];
switch (result) {
case TWTweetComposeViewControllerResultCancelled:
[self removeChild:colcol cleanup:YES];
break;
case TWTweetComposeViewControllerResultDone:
[[GCHelper sharedInstance] reportAchievementIdentifier:#"tweet_score" percentComplete:100.0];
[self removeChild:colcol cleanup:YES];
break;
default:
[self removeChild:colcol cleanup:YES];
break;
}
};
[appDelegate.viewController presentModalViewController:tweetSheet animated:YES];
}
else
{
// handle this case
}
}

Answer 1

In general, screen updates in CoreAnimation, UIKit, and OS X are deferred until the end of the current pass through the run loop. You are adding the CALayer, then doing some time-consuming work (setting up the TWTweetComposeViewController), then returning so the run loop can finish -- so there's no time for a screen update to happen in between.
Try setting up the TWTweetComposeViewController in a separate pass through the run loop, using dispatch_async(dispatch_get_main_queue(), ^{ /* your code here */ }).