问如何在后台使用app进行闹钟操作？

EN

- (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];
}