I am having an issue trying to have an ongoing location tracking enabled when the following conditions are in place:
Background fetch is disabled
App is killed
When the above happens, location updates are stopped. I tried to have my server send push notifications to wake the app up but they do not arrive if the app is killed.
What is puzzling is that a similar functionality seems to work just fine on WhatsApp (the live location). On WhatsApp, even if I disable background fetch and kill the app, it somehow manages to wake it up again to send updated location information.
Does anyone have any idea on what they are doing?
It seems WhatsApp could be using PushKit to get around this problem. According to this question:
WhatsApp could be using VOIP background mode along with PushKit for
solving this problem.
Voip pushes are:
delivered directly to the app.
considered high-priority notifications and are delivered without delay.
delivered even if the app was force-quit by the user.
I have also created a quick sample app to try this and it works like a charm. However, again according to the question linked, Apple doesn't really allow this solution:
Apple no longer allows the usage of the API for push notifications of non-VOIP apps. They do however allow WhatsApp to do it in their infinite fairness.
Use significant-change location services. It will work even the app is terminated.
Related
My problem is: I just can't make silent notifications work when a user has force-quit(swiped away) the app!
I guess the following is a fact: A silent push (with content-available:1) will NOT trigger application(_:didReceiveRemoteNotification:fetchCompletionHandler:) nor any other method (it will NOT launch the app) if the application was force-quit (swiped away) by the user! Can anyone prove this wrong?
I have made sure I've enabled Background Mode: Remote Notifications.
But what if non-silent notifications don't work for me? I need silent ones, I need to be able to run some checks before I show it! What If I want to check if the right user is logged on to my application after I receive a notification from remote server? (since I can't guarantee that when he logged out he successfully let the server know about it, so I assume the server doesn't know for sure)
What would be the right approach to take in my situation?
There are many questions about similar things, but not many people involved, I wonder why? I don't believe that I have such a rare case. Maybe my basic approach to solving this kind of problem is wrong? It doesn't seem to be a problem on Android platform at all!
I am using FCM as central point of sending out notifications, so if you say that PushKit can solve my problems, too bad that FCM doesn't support VoIP certificates. But, I wonder, can PushKit really solve this? Or Apple just designed it this way that when a user force-quit an app, it means that this app must shut up altogether with its ability to push remote notifications?!
I don't consider this a duplicate of Firebase silent notification does not start up a closed iOS app because what I am asking here is what would be the solution if you want to check if the user to whom the notification is addressed for corresponds to the user logged in to the application? It can be considered duplicate if it turns out that there is absolutely no solution for this on iOS platform.
You ask:
Or [has] Apple just designed it this way that when a user force-quit an app, it means that this app must shut up altogether with its ability to push remote notifications?
Yes, this is how it is designed. App Programming Guide for iOS: Understanding When Your App Gets Launched into the Background says:
In most cases, the system does not relaunch apps after they are force quit by the user. One exception is location apps, which in iOS 8 and later are relaunched after being force quit by the user. In other cases, though, the user must launch the app explicitly or reboot the device before the app can be launched automatically into the background by the system. When password protection is enabled on the device, the system does not launch an app in the background before the user first unlocks the device.
Is not possible. when the app is in background or suspended modes, you will have 30 sec to do some stuff. But if user kill app manually func didReceiveRemoteNotification will never called.
Upd:
When an iOS device receives a silent notification, the system wakes your app in the background and calls the application(_:didReceiveRemoteNotification:fetchCompletionHandler:) method of its app delegate. Your app has 30 seconds of wall-clock time to perform any tasks and call the provided completion handler. For more information, see Handling Notifications and Notification-Related Actions.
As stated clearly in Apple docs, beacon ranging can be done in background for a short period of time only, say up to 10 seconds by default or up to 3 minutes with the help of background task expiration handler. As per my app's use case, app needs to do beacon ranging for every 15 mins until user exits the region. I am thinking of using background push notification(silent push notification) for this purpose(assuming data connection is available on the device always). So the flow goes like this, upon user entering the region, app calls the server with device token, server sends silent push notification for every 15 minutes. Once app received push notification, it does beacon ranging within allowed period of time if needed. Question I have here is whether using push notification in background mode to do ranging is legal, will I face any issues during app store submission.
Note: Also I need to enable BLE background mode for the app, to read some characteristics from some BLE devices.
Technically you can do it, but Apple mostly rejects such app. One important thing you have to consider is that, if the app is manually killed by the user and not running in the background, then the app won't wake up with silent push notification. There is a workaround if you have VoIP push notifications it will wake the app even from the terminated state. But you might need strong reason while pushing it to AppStore.
If you misuse one of the background modes, the app will probably be rejected, saying that, I don't think silent push notifications were meant for: keep an iOS app in "Background" state by sending it a silent push notification every few minutes.
another thing is that silent push notifications are rate limited as described http://asciiwwdc.com/search?q=push+notification, so I'm not sure if they will be sent every few minutes.
Apple says that;
Silent notifications are not meant as a way to keep your app awake in
the background, nor are they meant for high priority updates. APNs
treats silent notifications as low priority and may throttle their
delivery altogether if the total number becomes excessive. The actual
limits are dynamic and can change based on conditions, but try not to
send more than a few notifications per hour.
You might want to see this article. The user talks about apps that use silent notification for triggering location tracking. But eventually it's a hack that Apple may reject some time in the future, so it's best to have a contingency plan. FWIW so far I haven't heard anyone reporting rejection.
So the official answer is don't do it, as for the why you can refer to Ashish's answer. The unofficial answer is if you can't change your business logic then do it at your own risk.
The iOS application I'm working on does the exact same thing with the exception that I'm using recording instead of a Beacon. Recording by iOS standards gives more issues in pushing the app to the app store.
But Apple did not reject this app. Although we still are facing some issues but they don't relate to your problem.
You can follow such a tutorial for further help apart from the answer you were looking for : iOS Push Notification Demysitfied
Also, I've done firing of local notifications, while the application is in the background. BLE even works if the app is killed by the system, when the OS receives some communication from your peripheral or central, iOS wakes your app up and executes the desired function, before putting your app back to sleep.
I'm developing a great feature for my app which requires HTTP requests to be sent periodically in background.
I have read already many articles and discussions here, but haven't come up with a solution because all suggestions I met on stackoverflow.com solve the problem only partially.
Let me explain in details what do I want my application to do.
Consider there is a website with API and I want to send requests (when app is in background mode) periodically to check the state of data on the website. And if the state of data is acceptable I would send Push Notification to user to notify him that data is correct at the moment.
Could someone propose a solution how to implement this idea in iOS app?
On iOS you can't do this, as you've described it. You don't get to schedule tasks to happen at regular intervals when your app is in the background or not running. You also don't get to control whether iOS decides to terminate your app when it's running in the background, so "not running" is a case you'd need to handle (you can't just keep running in the background as for long as you want).
I'm not sure I understand the server side of things though. If your server is manipulating the data until it's acceptable, and it can send push notifications, why does it need to wait for an incoming request from the phone? Why not just send the push when the data is ready? If the app decides what's "acceptable", maybe have the app tell the server what it wants so that the server knows when to send a push.
There are a couple of options that would get close to what you describe. If you implement the "background fetch" feature in your app, iOS will launch the app when it's not running and let it make network calls in the background. There's no guarantee of how often this happens, though. This is described in Apple's background execution docs
The other option is the "silent" push notification. If your server sends one of these, iOS can launch the app in the background to handle the notification. The app could make a network call if necessary. You can send these at whatever time you like, but Apple warns to not overdo it:
Silent notifications are not meant as a way to keep your app awake in the background, nor are they meant for high priority updates. APNs treats silent notifications as low priority and may throttle their delivery altogether if the total number becomes excessive. The actual limits are dynamic and can change based on conditions, but try not to send more than a few notifications per hour.
Silent pushes are described in Apple's push notification docs.
iOS Background Execution Limits
Questions
How do I keep my app running continuously in the background?
If I schedule a timer, how do I get it to fire when the screen is locked?
How do I run code in the background every 15 minutes?
How do I set up a network server that runs in the background?
How can my app provide an IPC service to another one of my app while it’s in the background?
Answer from Apple:
The short answer to all of these is You can’t. iOS puts strict limits on background execution. Its default behavior is to suspend your app shortly after the user has moved it to the background; this suspension prevents the process from running any code.
Official: https://developer.apple.com/forums/thread/685525
How does Whatsapp continue to receive notifications of received messages, even after you kill the app or restart the phone?
I am using an application that sends location coordinates, and it's for iOS, written in Swift.
My problem is that when I kill the app, the application stops sending coordinates. How I can make it restart automatically? For example, Whastapp, despite killing the app, if someone sends me a message, I receive the notification
I have also tried creating a widget app, but this is activated only when under the bar where the widget exists.
WhatsApp continues receiving PushNotifications. These are sent by Web Server and the App need not be active for it.
Coming to your requirement, you can use options like requestAlwaysAuthorization (to keep App awake in background to be able to send notifications). SignificantLocationChange, RegionMonitoringService, VisitService (to relaunch you app in the background if terminated).
Hope it helps.
Use this tutorial https://www.raywenderlich.com/123862/push-notifications-tutorial. you need to have one developer account to use push notification. It's easy to implement.
Is it possible to wake up a background application with a non ios notification center? e.g. if I were creating a calling or messaging application is it possible to wake the application via SMS.
Nope. If you want to call app outside the device, you should use APNS. On the device you can use local notification. Sending SMS to wake up app is kinda wrong. People don't like such solutions - imagine bunch of SMS every day for different apps. Sorry.
No.
If you have background code running, you can schedule a local notification to yourself. If the user clicks "Ok" then you will come to the foreground. See here for a description and sample code.
As far as I can tell, the only ways to launch an app without user input is via a custom URL handler or via an accessory. It doesn't sound like an accessory fits your use case. Sadly you can't open URLs from the background, so you can't use this to wake yourself.