iOS之本地通知 NSLocalNotification

      iOS 推送通知分为本地推送和远程推送通知，远程推送通知就类似于我们平时使用微信时，即使锁屏了，也能收到好友发送给我们的消息，然后在主屏幕显示一个alertview，远程推送需要远程服务端的支持，比较复杂. 本地推送相对比较简单，不需要服务端的支持。

       本地通知是NSLocalNotification 实现的，通过实例化一个NSLocalNotification类型的通知，同时设置通知的fireDate 属性，即通知的触发时间；设置timeZone属性，即时区；设置alertBody，显示的内容；设置alertAction;设置soundName，即推送发生时的声音；设置applicationIconBadgeNumber，即图标上的数字；设置userInfo属性，该属性是一个NSDictionary类型的变量。然后在使用UIApplication 的 实例方法scheduleLocalNotification：或 presentLocalNotificationNow: 推送通知。

      在Appdelegate的- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions中添加如下代码：

NSDate * itemDate = [NSDate date];
    
    UILocalNotification * localNotif = [[UILocalNotification alloc] init];
    if(localNotif == nil)
        return ;
    localNotif.fireDate = [itemDate dateByAddingTimeInterval:60];
    NSLog(@"fireDate is %@",localNotif.fireDate);
    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 dictionaryWithObjectsAndKeys:item.eventName,ToDoItemKey,@"Local Push reveived while running",MessageTitleKey ,nil];
    localNotif.userInfo = infoDict;
    [[UIApplication sharedApplication] scheduleLocalNotification:localNotif];
    NSLog(@"scheduledLocalNotifications are %@",[[UIApplication sharedApplication] scheduledLocalNotifications]);

 当应用程序收到本地推送通知是发调用Appdelegate的 -( void )application:( UIApplication *)application didReceiveLocalNotification:( UILocalNotification *)notification方法，在该方法中显示通知的内容：

-(void)application:(UIApplication *)application didReceiveLocalNotification:(UILocalNotification *)notification
{
    NSLog(@"application : didReceiveLocalNotificaiton:");
    NSString * itemName = [notification.userInfo objectForKey:ToDoItemKey];
    NSString * messageTitle = [notification.userInfo objectForKey:MessageTitleKey];
    [self _showAlert:itemName withTitle:messageTitle];
    NSLog(@"Receive Local Notification while the app is still running ...");
    NSLog(@"current notification is %@",notification);
    application.applicationIconBadgeNumber = notification.applicationIconBadgeNumber - 1;
}
-(void)_showAlert:(NSString *)pushmessage withTitle:(NSString *)title
{
    UIAlertView * alertView = [[UIAlertView alloc] initWithTitle:title message:pushmessage delegate:self cancelButtonTitle:@"OK" otherButtonTitles: nil];
    [alertView show];
}