How to show/hide UIImageView when I want - iphone

Question

I'm having a little problem with an iPhone app I'm currently developing.
When the user touch a button, it calls an IBAction named refreshQuestion, which is supposed to show an image hover the screen to ask the user to wait a moment, then it has to call another function, and finally it has to hide the image.
The problem is that the image won't appear. As well as the network activity indicator.
Any help?
Here is the code :
- (IBAction)refreshQuestion:(id)sender{
pleaseWait.hidden = NO;
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
[self loadData];
pleaseWait.hidden = YES;
[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
}
EDIT :
Here is my LoadData function :
- (void)loadData{
NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
NSString * idUtilisateur = [userDefaults objectForKey:#"idUtilisateur"];
NSString * stringUrlQuestion = [NSString stringWithFormat:#"http://www.mywebsiteURL"];
NSURL * urlQuestion = [NSURL URLWithString:stringUrlQuestion];
QuestionParser * parser = [[QuestionParser alloc] init];
[parser parseXMLAtURL:urlQuestion parseError:nil] ;
int nbQuestions = [parser.arrayOfQuestion count];
[parser release];
NSFetchRequest *requete = [[NSFetchRequest alloc] init];
NSEntityDescription *entite = [NSEntityDescription entityForName:#"Question" inManagedObjectContext:self.managedObjectContext];
[requete setEntity:entite];
NSSortDescriptor * sortDescriptor = [[NSSortDescriptor alloc] initWithKey:#"idQuestion" ascending:YES];
NSArray * sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor, nil];
[requete setSortDescriptors:sortDescriptors];
[sortDescriptor release];
[sortDescriptors release];
NSError * error;
NSMutableArray *mutableFetchResult = [[self.managedObjectContext executeFetchRequest:requete error:&error] mutableCopy];
[requete release];
if(mutableFetchResult == nil){
NSLog(#"Erreur viewWillAppear : %#", error);
}
questionDuJour = [mutableFetchResult objectAtIndex:0];
if (nbQuestions == 0){
UIAlertView* alertViewConnection = [[UIAlertView alloc] initWithTitle:#"Error" message:#"Error while retreiving data" delegate:self cancelButtonTitle:#"OK" otherButtonTitles:nil];
[alertViewConnection show];
[alertViewConnection release];
}
NSDateFormatter *outputFormatter = [[NSDateFormatter alloc] init];
[outputFormatter setDateFormat:#"EEEE d MMMM"];
NSLocale * localisation = [[[NSLocale alloc] initWithLocaleIdentifier:#"fr_FR"] autorelease];
[outputFormatter setLocale:localisation];
labelJour.text = [NSString stringWithFormat:#"%#",[outputFormatter stringFromDate:questionDuJour.dateQuestion]];
textQuestion.text = questionDuJour.textQuestion;
citation.text = [NSString stringWithFormat:#"%#",questionDuJour.citation];
labelAuteur.text = [NSString stringWithFormat:#"%#",questionDuJour.auteur];
[outputFormatter release];
NSLog(#"stop animating");
}

Answer 1

I think your code [self loadData] executes in microseconds.
Check by using this code alone,
pleaseWait.hidden = NO;
[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;
EDIT:
Check this, if you still get the same problem check whether you have assigned IBoutlet or not. Because what you are doing is the correct way.

Answer 2

Sounds like everything is executing on the UI Thread. Post your loadData method so we can see what its doing. Chances are you have to convert this method to use one of the asynchronous techniques which will return immediately and allow the UI thread to continue. You can then detect when its done loading the data and change the visibility of the image again.