float version = [[[UIDevice currentDevice] systemVersion] floatValue];
if (version >= 8.0) {
UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge categories:nil];
[[UIApplication sharedApplication] registerUserNotificationSettings:settings];
}
UIApplication *app = [UIApplication sharedApplication];
app.applicationIconBadgeNumber = 123;
iOS applicationIconBadgeNumber(后台app红色角标)
原文：http://my.oschina.net/123009/blog/512863