How to solve UIThread bloack problem in iPhone

Question

Hi,

I am creating an iPhone application where I need to show a login screen for few minutes, hence I created the custom view and added to the custom view controller which is added to the window for display. Now at the same time I need to check for some background database so, I am creating that in separate delegate and while after database operation is in finished it gives an callback to the main thread to display the new screen. But the first view is never getting displayed and my application directly lands up in the new view. Please find below my code snippet,

• (void)CheckForExistingData : (DatabaseSource *)theDatabaseConnection { BOOL isRecordExist = theDatabaseConnection.isrecordExist;

  // Release the connection.... [theDatabaseConnection release]; theDatabaseConnection = nil;

  if (isRecordExist == FALSE) {

  textLabel.text = @"Preparing the application for first time use, please wait...."; [activityIndicator startAnimating]; [self setNeedsDisplay];

  } else { // Now all categories are successfully downloaded, launch the category screen... sleep(2); // sleep for 1 second to allow to show the splash screen.... [self.viewController LaunchCategoryViewController:self]; }

}

Here CheckForExistingData is an callback mechanism which will be called from the other thread.

Answer 1

sleep() blocks your main thread, thus the UI has no chance to update. But you can always send messages delayed. In your case, it would look like this:

[self.viewController performSelector:@selector(LaunchCategoryViewController:) withObject:self afterDelay:2.0];

Answer 2

You need to exit your method to see anything displayed. Not sleep or wait on a synchronous network call.

That probably means you need to break your sequential code into multiple methods, the subsequent parts being called by a splash wait timer, the view button handler, or the async network activity completion callback.