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Showing posts with label Notification. Show all posts
Showing posts with label Notification. Show all posts

Which delegate method called when I click on push notifications?

Ans : 
Different app delegate method called depends on following scenarios

For silent notification : 

App is in Foreground
No system alert shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Background
System alert is shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Suspended
App state changes to Background
System alert is shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is Not Running because killed by user
System alert is shown
No callback is called

Normal Push Notification (no content-available) :

App is in Foreground
No system alert shown
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Background or Suspended
System alert is shown
No method is called, but when user tap on the push and the app is opened
application:didReceiveRemoteNotification:fetchCompletionHandler: is called

App is in Not Running
System alert is shown
No method is called, but when user tap on the push and the app is opened
application:didFinishLaunchingWithOptions: then application:didReceiveRemoteNotification:fetchCompletionHandler: are both called

Local Notification in iOS

Ans : 

Q.
 what the best way to Scheduled more than one notification but not remove the previous one?
A. Use different identifier

Different type of request access under UNAuthorizationOptions like .alert, .badge, .sound and .carplay.

let center =  UNUserNotificationCenter.current()a
center.requestAuthorization(options: [.alert, .sound, .badge]) { (result, error) in

 //handle result of request failure

}

UNNotificationRequest helps to create notification request. Which requires 3 information like an identifier, content and trigger.

1. identifier : It is unique for every notification. If we send another notification with same identifier it remove existing notification and replace it with new one.

2. content : display it in banner and main attributes are title, subtitle, body and attachment media. Using UNMutableNotificationContent we can define content.

3. trigger : the event that will trigger the notification to be displayed to the user. There are 3 classes as UNTimeIntervalNotificationTrigger,UNCalendarNotificationTrigger,UNLocationNotificationTrigger which are subclass of  UNNotificationTrigger.

example of creating local notification :

//get the notification center
let center =  UNUserNotificationCenter.current()

//create the content for the notification
let content = UNMutableNotificationContent()
content.title = " Jurassic Park"
content.subtitle = "Lunch"
content.body = "Its lunch time at the park, please join us for a dinosaur feeding"
content.sound = UNNotificationSound.default()

//notification trigger can be based on time, calendar or location
let trigger = UNTimeIntervalNotificationTrigger(timeInterval:2.0, repeats: false)

//create request to display
let request = UNNotificationRequest(identifier: "ContentIdentifier", content: content, trigger: trigger)

//add request to notification center
center.add(request) { (error) in
    if error != nil {
        print("error \(String(describing: error))")
    }
}

-> UNUserNotificationCenterDelegate having 2 methods which is used to display notification when app is in foreground. (WillPresent delegate method is used for display notification when app in foreground).



Explain Apple push notification working

Ans : Push notifications allow developers to reach users and perform small tasks even when users aren’t actively using an app.

In iOS 10, User can do following task :

  • Display a short text message
  • Play a notification sound
  • Set a badge number on the app’s icon
  • Provide actions the user can take without opening the app
  • Show a media attachment
  • Be silent, allowing the app to wake up in the background and perform a task
Now following steps to follow to configure push notification :

1. Create app id in developer account with your app bundle id. Push notification entitlement must be enabled for this app id. (or another way for go to App Settings > Capabilities and enable push notification switch). You also have to create CSR(Certificate Signing Request) file from your keychain and assign to this app id push notification feature in developer account.

2. Now in terms of coding, first we need to ask to user for allowing user notification. After allowing, we need to register for remote notification. If all goes good, system provides you 'token' which is address of this app for this device.

3. In code, first import usernotification. Then for registering for remote notification, in didFnishLaunchingWithOptions

UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge])  {
    (granted, error) in
   
       print("Permission granted: \(granted)")
    
       guard granted else { return }
       self.getNotificationSettings()

  }

 func getNotificationSettings()  {
       UNUserNotificationCenter.current().getNotificationSettings { (settings) in
       print("Notification settings: \(settings)")
       guard settings.authorizationStatus == .authorized else { return }
       UIApplication.shared.registerForRemoteNotifications()
  }


4. If registered for remote notification successfully, then one of the following two method will be called,

func application(_ application: UIApplication,
                 didRegisterForRemoteNotificationsWithDeviceToken deviceToken: Data)  {

       let tokenParts = deviceToken.map { data -> String in
              return String(format: "%02.2hhx", data)
        }

       let token = tokenParts.joined()
       print("Device Token: \(token)")
}

func application(_ application: UIApplication,
                 didFailToRegisterForRemoteNotificationsWithError error: Error)  {
  print("Failed to register: \(error)")
}

5. Device token is provided by APNS and this token will be converted to string. This device token shold be sent to application server or stored to database on server side.

Now lets study about payload or notification message,

Payload looks like :

{
  "aps": {
    "alert": "Breaking News!",
    "sound": "default",
    "link_url": "https://raywenderlich.com"
  }
}

aps is fixed key in payload dictionary json. aps is also dictionary itself.

alert : Display text message
sound : Which sound when notification come
link_url : custom key, we can any such custom key for data
badge : number of count of badge that is displayed on app icon
category : which type of custom action notification have

Payload maximum size is 4096 kb (4 mb).


Now what when notification comes

1. If app is closed didFinishLaunchingWithOptions is called.
2. If open in background or foreground, then didReceiveRemoteNotification is called.

For 1st case,

In didFinishLaunchingWithOptions method
// Check if launched from notification

if let notification = launchOptions?[.remoteNotification] as? [String: AnyObject] {

  let aps = notification["aps"] as! [String: AnyObject]
  _ = NewsItem.makeNewsItem(aps)

  (window?.rootViewController as? UITabBarController)?.selectedIndex = 1
}

For 2nd case,

In didReceiveRemoteNotification,

let aps = userInfo["aps"] as! [String: AnyObject]
  _ = NewsItem.makeNewsItem(aps)

Actionable Notification

Actionable notifications let you add custom buttons to the notification. You can put reply,retweet,like button as you seen our favourite apps. This type of notification can be defined by Category.

In this type notification, we have to register category like following instead of UIApplication.shared.registerForRemoteNotifications().

func registerForPushNotifications() {
  UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge]) {
    (granted, error) in   
    print("Permission granted: \(granted)")
 
    guard granted else { return }
 
    // 1
    let viewAction = UNNotificationAction(identifier: viewActionIdentifier,
                                          title: "View",
                                          options: [.foreground])
 
    // 2
    let newsCategory = UNNotificationCategory(identifier: newsCategoryIdentifier,
                                              actions: [viewAction],
                                              intentIdentifiers: [],
                                              options: [])
    // 3
    UNUserNotificationCenter.current().setNotificationCategories([newsCategory])
 
    self.getNotificationSettings()
  }
}


Above things is not enough for taking action on button. We have to add extension of UNUserNotificationCenterDelegate.

Silent Notification 

If we want to do something task without knowing to user in background, then we can send silent notification to user device. For this background modes of push notification must be checked. For push notification aps, there is key named content-available. That's value should be 1 for silent notification.

For more detail, click here.



Difference between Delegate and NSNotification

Ans :  A delegate uses protocol and creates a has-a relationship between two classes. Benefit of delegate is that we can return something back to the owning class.
Notification is like point to multi-point communication. Notification is one way  of message transmitting way.

Delegates create relationship between two classes. Notifications are used to send events to one or many classes.

We have to use delegate to specified known object. Notification for all object.

Delegate is like talking over telephone. Notification is like radio station.  

Coding of NSNotificationCenter :

[[NSNotificationCenter defaultCenter] addObjserver:self selector:@selector(useNotificationWithString:)  name:@”TimeOut” object:nil];

For BroadCast,

[[NSNotificationCenter defaultCenter] postNotificationName:@”TimeOut” object:nil userInfo:dict];

-(void) useNotificationWithString:(NSNotification *)notification
{
            dict = [notification userInfo];
}

To Remove observer,
[[NSNotificationCenter defaultCenter] removeObserver];