Fetch notification data on background without tap the notification - ios

Question

I try to get notification data on the background without tap the notification when I open the apps.
I already set Background Modes ON and checked "Background Fetch" and "Remote Notifications" in Capabilities.
and I already call this function
func userNotificationCenter(_ center: UNUserNotificationCenter,
didReceive response: UNNotificationResponse,
withCompletionHandler completionHandler: #escaping () -> Void) {
let userInfo = response.notification.request.content.userInfo
print(userInfo)
}
but the function not triggered when the notification comes and the function triggered only when I tapped the notification.
my expectation is: I can fetch the notification on the background without tap the notification when I open the app.

Answer 1

In order to configuring your project for Notification background download, enable below capabilities in XCode
don’t forget to set content-available to 1 in the actual notification from your server, to trigger the background download. If you fail to include this flag in the notification, your app will not receive any protocol method calls when the notification arrives.
There are four cases you need to handle:
Case1: Notification arrives, app running in background.
Case2: Notification arrives, app not running in background.
Case3: User taps on notification, app running in background.
Case4: User taps on notification, app not running in background.
Cases 1 and 3 call "didReceiveRemoteNotification" only while cases 2 and 4 provide the notification details in the launch options of "didFinishLaunchingWithOptions" and then call "didReceiveRemoteNotification".
If there is a case like user has killed your app manually, then case 2 will not occur. Your app will never be started in the background to fetch data until after the user chooses to launch it again.
We need to handle all application state cases differently. Below is the code:
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:
(NSDictionary *)launchOptions {
NSDictionary *data = [launchOptions objectForKey:UIApplicationLaunchOptionsRemoteNotificationKey];
if (data) {
self.appIsStarting = YES;
}
return YES
}
- (void)applicationWillResignActive:(UIApplication *)application {
self.appIsStarting = NO;
}
- (void)applicationDidEnterBackground:(UIApplication *)application {
self.appIsStarting = NO;
}
- (void)applicationWillEnterForeground:(UIApplication *)application {
self.appIsStarting = YES;
}
- (void)applicationDidBecomeActive:(UIApplication *)application {
self.appIsStarting = NO;
}
- (void) application:(UIApplication *)application didReceiveRemoteNotification:(NSDictionary *)userInfo fetchCompletionHandler:(void (^)(UIBackgroundFetchResult))completionHandler {
UIApplicationState state = [application applicationState];
if (state == UIApplicationStateBackground ||
(state == UIApplicationStateInactive &&
!self.appIsStarting)) {
NSDictionary *aps = userInfo[#”aps”];
if (aps) {
// perform the background fetch and
// call completion handler
}
}
} else if (state == UIApplicationStateInactive &&
self.appIsStarting) {
// user tapped notification
completionHandler(UIBackgroundFetchResultNewData);
} else {
// app is active
completionHandler(UIBackgroundFetchResultNoData);
}
}