准备工作

如果需要在APP中使用远程推送消息服务，需要通过apple member center内开通推送服务，创建与APP相关联的APP ID、开发与发布证书，APNs服务的开发与发布证书等，在开发调试之前，参考下面图中相关步骤完成准备工作。

证书生成方法及账号配置可参考下面的苹果官方文档链接。

CertificatePrepare

苹果相关指导文档：

Configuring Push Notifications

Local Notifications and Remote Notifications Programming Guide

概览

APNs Architecture

详细介绍

1.Register

在APP启动进入到Application launch接口时，调用注册API并且指定你感兴趣的推送通知类型，，iOS系统向APNs请求一个device token并且返回给APP。iOS 8.0之后注册接口稍有变化

-(void)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)options   {
    float sysVer = [[[UIDevice currentDevice] systemVersion] floatValue];
    if (sysVer >= 8.0) {
        if ([application respondsToSelector:@selector(registerUserNotificationSettings:)]) {
            UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:UIUserNotificationTypeBadge|
            UIUserNotificationTypeAlert categories:nil];
            [application registerUserNotificationSettings:settings];
        }  else {
            UIRemoteNotificationType myTypes = UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert;
            [application registerForRemoteNotificationTypes:myTypes];
        }
    } else {
            UIRemoteNotificationType myTypes = UIRemoteNotificationTypeBadge |UIRemoteNotificationTypeAlert;
            [application registerForRemoteNotificationTypes:myTypes];
    }
}

2.Send token

添加注册推送通知后，需要在AppDelegate.m中重写register notification相关回调方法，以获取APNs返回给此设备的Token，并将token通过APP自己的传输方式发送到APP所属Server上

- (void)application:(UIApplication *)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData *)token{

    //Update token to your server
    NSString* dt = [[token description] stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"<>"]];
    NSLog(@"RegisterForRemoteNotifications success UDID = %@", dt);
}

- (void)application:(UIApplication *)application didFailToRegisterForRemoteNotificationsWithError:(NSError *)error{

    //Check your provisioning profile for entitlements
    //Push not supported in the simulator
    NSLog(@"didFailToRegisterForRemoteNotifications");
}

需要注意的是在iOS8.0之后，需要先实现下面的方法及调用内容，上面的两个方法才会被调用

// This callback will be made upon calling -[UIApplication registerUserNotificationSettings:]. The settings the user has granted to the application will be passed in as the second argument.
- (void)application:(UIApplication *)application didRegisterUserNotificationSettings:(UIUserNotificationSettings *)notificationSettings
{
    [application registerForRemoteNotifications];
}

Device Token并不等同于UDID标识，它不是永久不变的，当iOS设备系统内容重置等情况下可能会发生变化，因此苹果官方建议在每次APP Launch时都要调用注册并检查一下token，如果发生变化应及时通知Server更新

3.Push notification to APNs（Server‘s Job）

Your Server需要一个有效证书才能和APNs连接(这个证书含有目标APP的Bundle identifier信息，前面已经介绍)。与APNs连接后，Your Server向APNs发送的通知带有设备token（由目标APP连接Your Server后发来的token），APNs以此找到目标设备，然后看目标设备里的目标程序有接受推送的证书，APNs以此验证通过后，发送通知给目标设备。

通知（Notification）Binary结构

其中APS dic保留Sound、Badge、Alert Keys，支持自定义，最大长度256bytes

Payload Binary

装载信息（Payload Message）JSON结构

其中APS dic保留Sound、Badge、Alert Keys，支持自定义，最大长度256bytes

Message Payload

载荷信息（Payload Message）Alert自定义

Alert Customizing

Server与APNs通信相关开源代码

C#开源 APNS-Sharp

java开源 javapns

OC开源 APNS-Pusher

4.Receive notification and dilivery

当Server成功发送一个通知到APNs并且验证通过后，APNs根据指定的Token发送通知到目标设备，此时目标设备有以下几种状态：

如果应用程序 isn't running,

iOS会处理这个消息，比如弹出一个框、在应用程序的icon上显示红色数字等。

如果用户此时通过点击弹框进入程序，iOS会启动程序调用application:didFinishLaunchingWithOptions,并且launchOptions包含远程消息的payload.

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions: (NSDictionary *)launchOptions {

    NSDictionary* payload = [launchOptions objectForKey:UIApplicationLaunchOptionsRemoteNotificationKey];
    if (payload){
        NSLog(@"startup from remote notification: %@",[payload description]);
        ....
    }
}

如果用户直接点击app icon进入程序，iOS会启动程序并同样调用application:didFinishLaunchingWithOptions，但是launchOptions不包含远程消息的payload。

如果应用程序is running in the foreground

- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)payload{
    
    NSLog(@"foreground remote notification: %@",[payload description]);
    ...
}

如果应用程序is running in the background

同样弹框，然后如果通过弹框进入程序，就会调用application:didReceiveRemoteNotification.
- (void)application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)payload{

    NSLog(@"background remote notification: %@",[payload description]);
    ...
}