我正在制作一个使用本地通知的应用程序。我正在尝试并使用两个实例。当我运行杀死应用程序时，只显示一个通知。这是应用程序 delegate.m 中的代码
- (void)applicationDidEnterBackground:(UIApplication *)application
{
//1
NSCalendar *gregcalendar2 = [[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *datecomponent2 = [gregcalendar2 components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit fromDate:[NSDate date]];
[datecomponent2 setYear:2013];
[datecomponent2 setMonth:6];
[datecomponent2 setDay:18];
[datecomponent2 setHour:16];
[datecomponent2 setMinute:58];
UIDatePicker *dd2 = [[UIDatePicker alloc]init];
[dd2 setDate:[gregcalendar2 dateFromComponents:datecomponent2]];
UILocalNotification *notification2 = [[UILocalNotification alloc]init];
[notification2 setAlertBody:@"two"];
[notification2 setFireDate:dd2.date];
[notification2 setTimeZone:[NSTimeZone defaultTimeZone]];
[application setScheduledLocalNotifications:[NSArray arrayWithObject:notification2]];
//2
NSCalendar *gregcalendar1 = [[NSCalendar alloc]initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *datecomponent1 = [gregcalendar1 components:NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit | NSHourCalendarUnit | NSMinuteCalendarUnit fromDate:[NSDate date]];
[datecomponent1 setYear:2013];
[datecomponent1 setMonth:6];
[datecomponent1 setDay:18];
[datecomponent1 setHour:16];
[datecomponent1 setMinute:59];
UIDatePicker *dd1 = [[UIDatePicker alloc]init];
[dd1 setDate:[gregcalendar1 dateFromComponents:datecomponent1]];
UILocalNotification *notification1 = [[UILocalNotification alloc]init];
[notification1 setAlertBody:@"one"];
[notification1 setFireDate:dd1.date];
[notification1 setTimeZone:[NSTimeZone defaultTimeZone]];
[application setScheduledLocalNotifications:[NSArray arrayWithObject:notification1]];
}