AWS Amplify Flutter: how to create platform endpoint? - swift

Question

Short version of my question: I have a Flutter mobile app that uses AWS Amplify to handle user
sign-up and log-in. Now I need to add push notification capability (with AWS SNS, APN etc.)
to the app, and in particular I need to let the app itself to create the platform endpoint.
So now I have to call the CreatePlatformEndpoint function in an Amplify Flutter
mobile app, and I don't know how to do it correctly. Any idea?
Here's what I've done so far: Firstly, I configured AWS Cognito and added Amplify
to my app so that the user can sign up and log in. The relevant code looks something
like the following:
// Sign Up
var userAttributes = {
CognitoUserAttributeKey.email: email,
};
await Amplify.Auth.signUp(
username: email,
password: password,
options: CognitoSignUpOptions(
userAttributes: userAttributes,
),
);
// Log In
var res = await Amplify.Auth.signIn(
username: email,
password: password,
);
if (res.isSignedIn) {
....
} else {
....
}
This part is successful and the code works all right.
Secondly, I configured APN, AWS SNS, and the iOS module of the app, then modified
AppDelegate to something like the following:
override func application(
_ application: UIApplication,
didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
) -> Bool {
GeneratedPluginRegistrant.register(with: self)
registerForNotifications()
return super.application(application, didFinishLaunchingWithOptions: launchOptions)
}
private func registerForNotifications() {
UNUserNotificationCenter.current().delegate = self
UNUserNotificationCenter.current().requestAuthorization(options: [.alert, .sound, .badge]) { [weak self] granted, _ in
guard granted else { return }
self?.getNotificationSettings()
}
}
private func getNotificationSettings() {
UNUserNotificationCenter.current().getNotificationSettings { settings in
guard settings.authorizationStatus == .authorized else { return }
DispatchQueue.main.async {
UIApplication.shared.registerForRemoteNotifications()
}
}
}
override func application(
_ application: UIApplication,
didRegisterForRemoteNotificationsWithDeviceToken tokenData: Data
) {
let token = tokenData.map { String(format: "%02.2hhx", $0) }.joined()
print("token: \(token)")
}
override func userNotificationCenter(
_ center: UNUserNotificationCenter,
willPresent notification: UNNotification,
withCompletionHandler completionHandler: #escaping (UNNotificationPresentationOptions) -> Void
) {
completionHandler([.badge, .sound, .alert])
}
This part is also successful. The iPhone can obtain and print the device token,
and when I manually create the endpoint in AWS Management Console and send a notification
from there, the iPhone can receive and show the notification.
Finally, I tried to let the app automatically create the endpoint in SNS when it got
the device token. I referenced this article, and managed to modify the
didRegisterForRemoteNotificationsWithDeviceToken method to the following:
override func application(
_ application: UIApplication,
didRegisterForRemoteNotificationsWithDeviceToken tokenData: Data
) {
let token = tokenData.map { String(format: "%02.2hhx", $0) }.joined()
print("token: \(token)")
let credentialsProvider = AWSCognitoCredentialsProvider(regionType: ......, identityPoolId: ".........")
let configuration = AWSServiceConfiguration(region: ......, credentialsProvider: credentialsProvider)
AWSServiceManager.default().defaultServiceConfiguration = configuration
let appArn = "arn:aws:sns:........"
let platformEndpointRequest = AWSSNSCreatePlatformEndpointInput()!
platformEndpointRequest.customUserData = "........."
platformEndpointRequest.token = token
platformEndpointRequest.platformApplicationArn = appArn
let sns = AWSSNS.default()
sns.createPlatformEndpoint(platformEndpointRequest) { response, error in
....
}
}
This part is only partially successful. The endpoint is indeed created in SNS,
and I can verify this in AWS Management Console. But there are serious problems:
the user is logged out after the above code is executed
when the user tries to log back in, the app crashes with an "unexpectedly found nil" exception
Here's the crash log:
AWSMobileClient/AWSMobileClient+SignIn.swift:66: Fatal error: Unexpectedly found nil while unwrapping an Optional value
AWSMobileClient/AWSMobileClient+SignIn.swift:66: Fatal error: Unexpectedly found nil while unwrapping an Optional value
* thread #4, queue = 'NSOperationQueue 0x107d22800 (QOS: UNSPECIFIED)', stop reason = Fatal error: Unexpectedly found nil while unwrapping an Optional value
frame #0: 0x000000019b861060 libswiftCore.dylib`_swift_runtime_on_report
libswiftCore.dylib`_swift_runtime_on_report:
-> 0x19b861060 : ret
libswiftCore.dylib`_swift_reportToDebugger:
0x19b861064 : b 0x19b861060 ; _swift_runtime_on_report
libswiftCore.dylib`_swift_shouldReportFatalErrorsToDebugger:
0x19b861068 : adrp x8, 324077
0x19b86106c : ldrb w0, [x8, #0x611]
Target 0: (Runner) stopped.
I think maybe the defaultServiceConfiguration = configuration thing conflicts
with Amplify, so I try removing that part and modify the code to:
override func application(
_ application: UIApplication,
didRegisterForRemoteNotificationsWithDeviceToken tokenData: Data
) {
let token = tokenData.map { String(format: "%02.2hhx", $0) }.joined()
print("token: \(token)")
let appArn = "arn:aws:sns:........"
let platformEndpointRequest = AWSSNSCreatePlatformEndpointInput()!
platformEndpointRequest.customUserData = "........."
platformEndpointRequest.token = token
platformEndpointRequest.platformApplicationArn = appArn
let sns = AWSSNS.default()
sns.createPlatformEndpoint(platformEndpointRequest) { response, error in
....
}
}
but then the code crashes at the createPlatformEndpoint call, and here's the crash log:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'The service configuration is `nil`. You need to configure `awsconfiguration.json`, `Info.plist` or set `defaultServiceConfiguration` before using this method.'
*** First throw call stack:
(0x197c1f128 0x1ab932480 0x102d7fcf4 0x197857298 0x1977faf90 0x102d7fb5c 0x102c875a0 0x102c86e4c 0x102c872c0 0x19a4d8c34 0x1978562b0 0x197857298 0x197805ce4 0x197b9e170 0x197b985d0 0x197b976a8 0x1ae247570 0x19a4b5370 0x19a4ba8ec 0x102c88400 0x197876140)
libc++abi: terminating with uncaught exception of type NSException
* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGABRT
frame #0: 0x00000001c38b47b0 libsystem_kernel.dylib`__pthread_kill + 8
libsystem_kernel.dylib`__pthread_kill:
-> 0x1c38b47b0 : b.lo 0x1c38b47cc ;
0x1c38b47b4 : stp x29, x30, [sp, #-0x10]!
0x1c38b47b8 : mov x29, sp
0x1c38b47bc : bl 0x1c38911fc ; cerror_nocancel
Target 0: (Runner) stopped.
So what should I do? What's the correct way to create an endpoint in an Amplify Flutter app?

Answer 1

OK, I'll answer my own question. I asked the Amplify-Flutter people and learned that there was currently no way to do what I want. I was advised to create a feature request ticket in their repository. I decided to turn to another approach, i.e. creating a Lambda that did the job on the backend, and it worked fine.