Silent notifications work via Background modes and content available flag, but only if the app is in background.
Is it possible to know if/when the user received the notification, even when the app is suspended(not in background) ?
The system does not automatically launch your app if the user has force-quit it. In that situation, the user must relaunch your app or restart the device before the system attempts to launch your app automatically again.
Here is the relevant section from the documentation:
application:didReceiveRemoteNotification:fetchCompletionHandler:
Use this method to process incoming remote notifications for your app.
Unlike the application:didReceiveRemoteNotification: method, which is
called only when your app is running in the foreground, the system
calls this method when your app is running in the foreground or
background. In addition, if you enabled the remote notifications
background mode, the system launches your app (or wakes it from the
suspended state) and puts it in the background state when a push
notification arrives. However, the system does not automatically
launch your app if the user has force-quit it. In that situation, the
user must relaunch your app or restart the device before the system
attempts to launch your app automatically again.
Related
I have implemented application:didReceiveRemoteNotification:fetchCompletionHandler:, which is necessary to run after receiving a push notification. I have also turned on "Background Fetch" and "Remote notifications" background modes. And my push notifications include the content-available flag, set to 1.
If my app is in the Active, Background or Suspended state, this function gets called appropriately and the app temporarily moves into the Inactive state. However, if my app has been purged from the Suspended state due to a low memory issue (i.e. the user has opened a number of other apps since launching my app, a fairly common occurrence), it moves into the Not Running state. At that point, it doesn't call the didReceiveRemoteNotifications function.
The documentation for this function states:
If you enabled the remote notifications background mode, the system launches your app (or wakes it from the suspended state) and puts it in the background state when a remote notification arrives. However, the system does not automatically launch your app if the user has force-quit it. In that situation, the user must relaunch your app or restart the device before the system attempts to launch your app automatically again.
The scenario where the user force quits the app and so the app doesn't call this function is acceptable. But what I'm seeing instead is if the system terminates the app for a fairly common reason, then this function doesn't get called.
I've also tried implementing application:didReceiveRemoteNotification:, the deprecated function, to see if that gets called when the app is in the Not Running state. It doesn't.
When i reboot my phone without opening my app, and send a remote notification with 'content-available' bit, my app is not launched or invoke the delegate. But I can get the notification alert. The app was even launched for scheduled background fetch! Once I started my app by tap icon, the delegate is invoked as expected even if my app is in background or killed(not force quit).
Am I misunderstanding Apple's doc of this method or I'm missing something in my implementation?
It's running on iOS 9.3.1.
Use this method to process incoming remote notifications for your app.
Unlike the application:didReceiveRemoteNotification: method, which is
called only when your app is running in the foreground, the system
calls this method when your app is running in the foreground or
background. In addition, if you enabled the remote notifications
background mode, the system launches your app (or wakes it from the
suspended state) and puts it in the background state when a push
notification arrives. However, the system does not automatically
launch your app if the user has force-quit it. In that situation, the
user must relaunch your app or restart the device before the system
attempts to launch your app automatically again.
I'm implementing didReceiveRemoteNotification. I'm also saving these notifications locally. But I noticed if I'm at the home screen and don't open the notification, this function never gets called, and I can't save the notification. Any ideas?
You have to implement application:didReceiveRemoteNotification:fetchCompletionHandler: instead of application:didReceiveRemoteNotification:. See official documentation here:
Use this method to process incoming remote notifications for your app.
Unlike the application:didReceiveRemoteNotification: method, which is
called only when your app is running in the foreground, the system
calls this method when your app is running in the foreground or
background. In addition, if you enabled the remote notifications
background mode, the system launches your app (or wakes it from the
suspended state) and puts it in the background state when a remote
notification arrives. However, the system does not automatically
launch your app if the user has force-quit it. In that situation, the
user must relaunch your app or restart the device before the system
attempts to launch your app automatically again.
Also make sure to enable "remote notifications background mode", like stated in the documentation. Edit Info.plist and check the "Enable Background Modes" and "Remote notifications" check boxes:
It looks like no matter I return UIBackgroundFetchResultNewData or UIBackgroundFetchResultNoData from performFetchWithCompletionHandler, it clears all previous notifications (local or push) for my app. This is not acceptable for me.
Anyone knows how do I do fetch and not make previous notifications cleared (disappear)?
My guess here is that you had a background fetch that was setting your badge number to 0, if that ever happens all your notifications are cleared.
Source: Apple's AppDelegate API Reference
application(_:didReceiveRemoteNotification:fetchCompletionHandler:)
Tells the app that a remote notification arrived that indicates there is data to be fetched. Use this method to process incoming remote notifications for your app. Unlike the
application(_:didReceiveRemoteNotification:)
method, which is called only when your app is running in the foreground, the system calls this method when your app is running in the foreground or background. In addition, if you enabled the remote notifications background mode, the system launches your app (or wakes it from the suspended state) and puts it in the background state when a remote notification arrives. However, the system does not automatically launch your app if the user has force-quit it. In that situation, the user must relaunch your app or restart the device before the system attempts to launch your app automatically again.
If the user opens your app from the system-displayed alert, the system may call this method again when your app is about to enter the foreground so that you can update your user interface and display information pertaining to the notification.
Note: You need to make sure that the app is checking for the state before settings the application's badge number to 0. Test the below cases:
Application running, receives a notification
Application terminated, receives a notification
Launch app directly from app icon
Launch app from notification received
Knowing the difference between the 3 approached below is essential in your use case.
Checking the notification object received in application(_:didReceiveRemoteNotification:)
Checking the notification object received in application(_:didReceiveRemoteNotification:fetchCompletionHandler:)
Checking the didFinishLaunchingWithOptions for UIApplicationLaunchOptionsRemoteNotificationKey
I have tried various samples from the web (the last one being this one) in order to get a better understanding of NSUrlSession.
What I was hoping to see: file downloads will continue even if the app that triggered them gets killed (for instance by the user through the task manager). However this does not seem to happen.
Is this a configuration issue or does background file transfer not work if the app gets terminated?
I thought the whole idea was that iOS will restart the app.
If the system kills your app and your background session has active downloads, your downloads will continue and the system will launch your app when the downloads complete. However, if a user force quits your app, all tasks get cancelled.
Documentation for backgroundSessionConfigurationWithIdentifier:
If an iOS app is terminated by the system and relaunched, the app can
use the same identifier to create a new configuration object and
session and retrieve the status of transfers that were in progress at
the time of termination. This behavior applies only for normal
termination of the app by the system. If the user terminates the app
from the multitasking screen, the system cancels all of the session’s
background transfers. In addition, the system does not automatically
relaunch apps that were force quit by the user. The user must
explicitly relaunch the app before transfers can begin again.
No - the app is not relaunched for background downloads when the user has force quit.
The iOS8 documentation for application:didReceiveRemoteNotification:fetchCompletionHandler: says:
Use this method to process incoming remote notifications for your app.
Unlike the application:didReceiveRemoteNotification: method, which is
called only when your app is running in the foreground, the system
calls this method when your app is running in the foreground or
background. In addition, if you enabled the remote notifications
background mode, the system launches your app (or wakes it from the
suspended state) and puts it in the background state when a push
notification arrives. However, the system does not automatically
launch your app if the user has force-quit it. In that situation, the
user must relaunch your app or restart the device before the system
attempts to launch your app automatically again.