Fire a method ever 24 hours

问题

I am trying to fire a method once a day at a given time. I've tried a few things but I can't really make it work. any advice would be appreciated. Also, it would be ideal if it would fire regardless of if the app is open or not. Is this possible?

回答1:

UILocalNotification will let you fire a notification (but not a method) when your app is running in the background, or will call a delegate method you implement (application:didReceiveLocalNotification:) if the app is running in the foreground, or will call a method you must implement (application:didFinishLaunchingWithOptions:) when the user responds to the alert. Other than this, you will not be able to call a method when the app is not in the foreground, you will only be able to fire the the notification (which can display the badge, play a sound, etc).

By the way, consider filing a bug report with apple if this is a feature you want. I would like the ability to run methods in the background based on local notifications, without waiting for the user to respond first.

See Apple's example code:

- (void)scheduleNotificationWithItem:(ToDoItem *)item interval:(int)minutesBefore {
    NSCalendar *calendar = [NSCalendar autoupdatingCurrentCalendar];
    NSDateComponents *dateComps = [[NSDateComponents alloc] init];
    [dateComps setDay:item.day];
    [dateComps setMonth:item.month];
    [dateComps setYear:item.year];
    [dateComps setHour:item.hour];
    [dateComps setMinute:item.minute];
    NSDate *itemDate = [calendar dateFromComponents:dateComps];
    [dateComps release];

    UILocalNotification *localNotif = [[UILocalNotification alloc] init];
    if (localNotif == nil)
        return;
    localNotif.fireDate = [itemDate addTimeInterval:-(minutesBefore*60)];
    localNotif.timeZone = [NSTimeZone defaultTimeZone];

    localNotif.alertBody = [NSString stringWithFormat:NSLocalizedString(@"%@ in %i minutes.", nil),
         item.eventName, minutesBefore];
    localNotif.alertAction = NSLocalizedString(@"View Details", nil);

    localNotif.soundName = UILocalNotificationDefaultSoundName;
    localNotif.applicationIconBadgeNumber = 1;

    NSDictionary *infoDict = [NSDictionary dictionaryWithObject:item.eventName forKey:ToDoItemKey];
    localNotif.userInfo = infoDict;

    [[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
    [localNotif release];
}

来源：https://stackoverflow.com/questions/6047981/fire-a-method-ever-24-hours