Is it possible to use both background fetching and silent remote notifications at the same time to maximize the number of background activity? Apple says they put limits on both but using both would be a work around to such limits right? If I set the background fetch interval to the minimum and then send a silent notification every 15 minutes, how would this work?
Yes, you can set both. But remember that the background fetch interval is just an indication to iOS. iOS determines when background fetches occur based on its own criteria (including the phone being plugged in or not, being unlocked or not, doing any other work that woke up the CPU and radios, etc.).
Likewise, delivery of silent remote notifications is not guaranteed.
Remember that in any case, you want to minimise power consumption while in the background. All those restrictions Apple sets are there for this reason. Trying to bypass them has a cost.
Related
How do Messenger and other apps refresh themselves in the background regularly and display every single notification?
Is it a server that sends a signal to the app on a regular basis to refresh their data in the background?
Mostly applications use multiple ways to update notifications:
Send push notification, if in case you want to inform user about the activity.
Send silent push notification, if in case you don’t want to inform user that something happened in background. ( "content-available" : 1 )
IMPORTANT
Background update notifications are not meant as a way to keep your app awake in the background beyond quick refresh operations, nor are they meant for high priority updates. APNs treats background update 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.
Source: https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/CreatingtheNotificationPayload.html
But still most apps use this.
Run/schedule a background task to perform some action.
I am working on an app that keeps people updated with news around a certain event. That means that I don't want to run background fetches all the time. And one more thing, what I understood from Apple's background execution documentation is that it is not guarantee to have those fetch operations scheduled as the minimum fetch interval set.
So is there any way to schedule those fetches guaranteeing those fetch intervals? I know of silent push notifications but I don't want to have a server side solution.
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
I have developed a small iBeacon based application, when the application detects one of our iBeacons makes a call to a web service to obtain a data set and send a local notification to the user. All this is working correctly.
I have now raised the idea that these local notifications could vary over short time intervals, with new content. The problem is that if the user does not leave the region of the iBeacon and reenters, the application will not "wake up" and the user will not receive the new updated notification.
I do not know if this could be solved somehow or actually the approach to make something like that should not be related to technology of iBeacons.
I'm really lost and do not know if anyone would know advise me on how to raise it.
You can schedule local notifications to be delivered at a specific time: use the fireDate and timeZone properties of the UILocalNotification, and then use scheduleLocalNotification instead of the presentLocalNotificationNow method of the UIApplication.
With that in mind you could do this: upon an "enter" event, retrieve a few notifications to be showed to the user over a certain time period while they remain in the zone, schedule them appropriately and let iOS do the delivering.
If the user exits the zone before all the notifications are shown, you can cancel the remaining local notifications using cancelLocalNotification or cancelAllLocalNotifications methods.
In order to do this, you need to get the app to run in the background while beacons are in the vicinity. This would allow you to periodically check for updated content associated with the beacon and then display notifications under two conditions:
When a beacon first appears, and there is a message associated with that beacon.
The message associated with the beacon above changes during the time the beacon is still visible.
As you mention, the second item is a problem, because you need a way to continually check to see if there is updated content despite the fact that iOS will suspend your app within 5 seconds of beacon detection in the background.
A few options, each of which have downsides:
You can use a custom hardware beacon that changes its identifier every minutes or so (e.g. the minor goes back and forth between 0 and 1). This would allow you to monitor two regions and re-trigger on each every minute the beacon is in the vicinity. Downside: This requires building a custom beacon.
You can make your app request an extra 3 minutes of background running time during which you can check for changed messages. Downside: You only get three minutes to display changed messages.
You can specify extra background modes in your .plist so you can continue running in the background. Downside: Apple won't approve your app for distribution in the store unless you have a good reason to run in the background (e.g. a navigation app or a music player app.)
You can send a push notification to your app each time the message changes, which would wake up your app in the background so you could display an updated notification if a beacon is in the vicinity. Downside: Setting up push notifications are a bit complex, delivery can be slow, and is not guaranteed.
Read here for more info on some of these options: http://developer.radiusnetworks.com/2014/11/13/extending-background-ranging-on-ios.html