iOS本地通知：UILocalNotification

2021-07-03 05:40:00

在去年做过一个小App，其中使用的关键功能就是向用户发送本地通知，可惜当时没有写博客的习惯，所以没有将对应的知识记录下来。最近又遇到了该功能的使用，这一次果断写个博客做下有关UILocalNotification的笔记。

首先是添加一个本地通知到系统中，代码如下：

    // 初始化本地通知对象
    UILocalNotification *notification = [[UILocalNotification alloc] init];
    if (notification) {
        // 设置通知的提醒时间
        NSDate *currentDate   = [NSDate date];
        notification.timeZone = [NSTimeZone defaultTimeZone]; // 使用本地时区
        notification.fireDate = [currentDate dateByAddingTimeInterval:5.0];
        
        // 设置重复间隔
        notification.repeatInterval = kCFCalendarUnitDay;
        
        // 设置提醒的文字内容
        notification.alertBody   = @"Wake up, man";
        notification.alertAction = NSLocalizedString(@"起床了", nil);
        
        // 通知提示音 使用默认的
        notification.soundName= UILocalNotificationDefaultSoundName;
        
        // 设置应用程序右上角的提醒个数
        notification.applicationIconBadgeNumber++;
        
        // 设定通知的userInfo，用来标识该通知
        NSMutableDictionary *aUserInfo = [[NSMutableDictionary alloc] init];
        aUserInfo[kLocalNotificationID] = @"LocalNotificationID";
        notification.userInfo = aUserInfo;
        
        // 将通知添加到系统中
        [[UIApplication sharedApplication] scheduleLocalNotification:notification];
    }

上面的alertBody是设备收到本地通知时横额或锁屏时的主要文字内容，alertActions是锁屏时显示的slide to后面的文字内容。例如：

iOS本地通知：UILocalNotification

repeatInterval表示通知的重复间隔，在SDK中定义如下：

@property(nonatomic) NSCalendarUnit repeatInterval;      // 0 means don‘t repeat

其取值主要有：

        NSCalendarUnitEra                = kCFCalendarUnitEra,
        NSCalendarUnitYear               = kCFCalendarUnitYear,
        NSCalendarUnitMonth              = kCFCalendarUnitMonth,
        NSCalendarUnitDay                = kCFCalendarUnitDay,
        NSCalendarUnitHour               = kCFCalendarUnitHour,
        NSCalendarUnitMinute             = kCFCalendarUnitMinute,
        NSCalendarUnitSecond             = kCFCalendarUnitSecond,
        NSCalendarUnitWeekday            = kCFCalendarUnitWeekday,
        NSCalendarUnitWeekdayOrdinal     = kCFCalendarUnitWeekdayOrdinal,

分别表示一个世纪、一年、一个月等等，0表示不重复。具体可以查看CFCalendar Reference

repeatInterval的下限应该是NSCalendarUnitMinute，即每分钟重复发送一次通知。

如果设置为NSCalendarUnitSecond，那么消息不会重复，每秒发送一次通知，iOS系统当然不会容许这样的存在了。

这里比较不好的一点是该值不能自定义（很遗憾，NSCalendarUnit是个枚举类型），例如你不能塞个10.0给它从而希望它每十秒重复一次。所以如果你想每20分钟发送一次通知，一小时内发送3次，那么只能同时设定三个通知了。

上面的代码运行后，5秒钟之后就可以收到一个本地通知。

在收到通知后，调用程序委托中的下列方法处理：

-(void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification{
    NSLog(@"Application did receive local notifications");
    
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Hello" message:@"welcome" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
    [alert show];
}

注意这个方法只有在程序启动之后才会执行，因此当程序处于后台时，该方法不会执行。

有一点需要注意，如果我们的应用程序给系统发送的本地通知是周期性的，那么即使把程序删了重装，之前的本地通知在重装时依然存在（没有从系统中移除）。例如，我们在viewDidLoad方法中启动添加本地通知的方法，多跑几次，然后把程序在模拟器中删除，再重新跑，并用下列方法输出所有的本地通知：

    NSArray *localNotifications = [[UIApplication sharedApplication] scheduledLocalNotifications];
    NSLog(@"%@", localNotifications);

控制台输出：

2014-03-14 15:46:37.145 LocalNotificationDemo[4419:60b] (
    "<UIConcreteLocalNotification: 0xa32ce30>{fire date = Friday, March 14, 2014 at 3:38:16 PM China Standard Time, time zone = Asia/Chongqing (GMT+8) offset 28800, repeat interval = NSDayCalendarUnit, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, March 15, 2014 at 3:38:16 PM China Standard Time, user info = {\n    ClockID = LocalNotificationID;\n}}",
    "<UIConcreteLocalNotification: 0xa32dfc0>{fire date = Friday, March 14, 2014 at 3:44:45 PM China Standard Time, time zone = Asia/Chongqing (GMT+8) offset 28800, repeat interval = NSDayCalendarUnit, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, March 15, 2014 at 3:44:45 PM China Standard Time, user info = {\n    ClockID = LocalNotificationID;\n}}",
    "<UIConcreteLocalNotification: 0xa32e470>{fire date = Friday, March 14, 2014 at 3:44:55 PM China Standard Time, time zone = Asia/Chongqing (GMT+8) offset 28800, repeat interval = NSDayCalendarUnit, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, March 15, 2014 at 3:44:55 PM China Standard Time, user info = {\n    ClockID = LocalNotificationID;\n}}",
    "<UIConcreteLocalNotification: 0xa32e950>{fire date = Friday, March 14, 2014 at 3:45:13 PM China Standard Time, time zone = Asia/Chongqing (GMT+8) offset 28800, repeat interval = NSDayCalendarUnit, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, March 15, 2014 at 3:45:13 PM China Standard Time, user info = {\n    ClockID = LocalNotificationID;\n}}",
    "<UIConcreteLocalNotification: 0xa32edb0>{fire date = Friday, March 14, 2014 at 3:45:29 PM China Standard Time, time zone = Asia/Chongqing (GMT+8) offset 28800, repeat interval = NSDayCalendarUnit, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, March 15, 2014 at 3:45:29 PM China Standard Time, user info = {\n    ClockID = LocalNotificationID;\n}}",
    "<UIConcreteLocalNotification: 0xa32e870>{fire date = Friday, March 14, 2014 at 3:46:28 PM China Standard Time, time zone = Asia/Chongqing (GMT+8) offset 28800, repeat interval = NSDayCalendarUnit, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, March 15, 2014 at 3:46:28 PM China Standard Time, user info = {\n    ClockID = LocalNotificationID;\n}}"
)

可以看到之前发送的本地通知一直滞留在系统中。

不只是模拟器，在iOS设备上也是这样，博主之前的App在设备上重装时以前的本地通知会继续发送。

因此我们需要取消通知的方法，当然该对象也会在scheduledLocalNotifications数组中移除。

取消方法分为两种。

第一种比较暴力，直接取消所有的本地通知：

[[UIApplication sharedApplication] cancelAllLocalNotifications];

这个适合在App重装时第一次启动的时候，或还原程序默认设置等场合下使用。

第二种方法是针对某个特定通知的：

- (void)cancelLocalNotification:(UILocalNotification *)notification NS_AVAILABLE_IOS(4_0);

这时就需要通知有一个标识，这样我们才能定位是哪一个通知。可以在notification的userInfo（一个字典）中指定。

例如：

-(void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification{
    NSLog(@"Application did receive local notifications");
    
    // 取消某个特定的本地通知
    for (UILocalNotification *noti in [[UIApplication sharedApplication] scheduledLocalNotifications]) {
        NSString *notiID = noti.userInfo[kLocalNotificationID];
        NSString *receiveNotiID = notification.userInfo[kLocalNotificationID];
        if ([notiID isEqualToString:receiveNotiID]) {
            [[UIApplication sharedApplication] cancelLocalNotification:notification];
            return;
        }
    }
    
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Hello" message:@"welcome" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil, nil];
    [alert show];
}

最后建议本地通知不要发得太频繁，不然用户会觉得非常的烦。

参考的文章和资料：

IOS本地通知

CFCalendar Reference

iOS: 枚举类型 enum,NS_ENUM,NS_OPTIONS

iOS本地通知：UILocalNotification,布布扣,bubuko.com

iOS本地通知：UILocalNotification

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