IOS基础之——添加本地通知（UILocalNotification）

本地通知（local notifacation）用于向用户提示一条消息——即使应用没有运行，用户也可以收到本地通知。

应用还可以通过后台服务器实现推送消息（push notification）。本篇只讨论本地通知，不讨论推送消息。

实现本地通知非常简单，首先需要创建一个UILocalNotification 对象并设置其显示内容和提醒时间，然后调用UIApplication单例对象的scheduleLocalNotification：方法注册该通知就可以了。

-（IBAction）addReminder:(id)sender{      NSDate *date = self.dataPicker.date;      UILocalNotification *notification = [[UILocalNotification alloc] init];    notification.alertBody = @"Hypnotize me!";    notification.fireDate = date;[[UIApplication sharedApplication] scheduleLocalNotification:notification];}

dataPicker是一个时间选择器，选择时间后按下按钮，就会在设置的时间到来时收到本地通知。

为了看到本地通知，必须将关闭应用，按home键使应用到后台。当到达时间后会弹出本地提醒。

实际上，达到了相应的时间，我们并没有收到预期的提醒，因为通知需要得到系统的权限，在控制台上会看到下面一段话：

2014-06-07 11:14:16.663 CCA-TV[735:149070] Attempting to schedule a local notification {fire date = Saturday, June 7, 2014 at 11:14:21 Pacific Daylight Time, time zone = America/Los_Angeles (PDT) offset -25200 (Daylight), repeat interval = 0, repeat count = UILocalNotificationInfiniteRepeatCount, next fire date = Saturday, June 7, 2014 at 11:14:21 Pacific Daylight Time, user info = (null)} with an alert but haven't received permission from the user to display alerts

那么我们就需要在代码中添加以下的内容，才能顺利收到本地通知：

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {    // Override point for customization after application launch.        if ([UIApplication instancesRespondToSelector:@selector(registerUserNotificationSettings:)]) {        [[UIApplication sharedApplication] registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeAlert|UIUserNotificationTypeBadge|UIUserNotificationTypeSound categories:nil ]];    }}