Game Center achievement notification repeats

Question

I am integrating Game Center onto my application, and I've done everything right, it's well but I have a problem. When an user completes an achievement, I wanted to add a notification. And I did manage to do that like this :

GKAchievement *achievement = [[GKAchievement alloc] initWithIdentifier:@"theFirstAchievement"];
achievement.percentComplete = sharedApp.firstAchievement = sharedApp.firstAchievement + 50;
[achievement reportAchievementWithCompletionHandler:^(NSError *error)
    {
        if (error != nil)
        {
            NSLog(@"achievement failed");
        }
        else
        {
            NSLog(@"achievement succeded");
        }
     }];
if (achievement.percentComplete == 100.0) 
{
   [GKNotificationBanner showBannerWithTitle:@"Achievement Unlocked:" message:@"Master Question Master!" completionHandler:nil];
}

My problem is, I don't know if I'm doing something wrong, but it is supposed to show a notification once, but, if I close my application and reopen, when I complete the achievement again it shows the notification again, even though it was already completed in my game center! What am I doing wrong? Thanks!

Answer 1

Look at this bit:

if (achievement.percentComplete == 100.0) 

This means that if the achievement percentage completion is 100%, show a banner. However, when you open the app again, and it reads the percentage, the percentage is still 100%, so it shows the banner again.

You'll have to keep a record of which achievements have been earned and awarded

I'd suggest something like this:

BOOL awarded = [[NSUserDefaults standardUserDefaults] boolForKey:@"theFirstAchievement"];
if (achievement.percentComplete == 100.0 && !awarded) 
{
   [GKNotificationBanner showBannerWithTitle:@"Achievement Unlocked:" message:@"Master Question Master!" completionHandler:nil];
    [[NSUserDefaults standardUserDefaults] setBool:YES forKey:@"theFirstAchievement"];
    [[NSUserDefaults standardUserDefaults] synchronize];
}