How to get "Apps Instance Id" in Flutter

The Firebase Instance ID can be fetched using -instanceIDWithHandler on iOS or getInstanceId on Android.

At the time of writing, I am not aware of a standalone plugin that does this, meaning that you have two options:

• Write your own plugin that wraps the native implementations of those methods
• Use the firebase_messaging Flutter plugin that happens to expose the Instance ID via its getToken() method

If you go the firebase_messaging route (mind you, it means you're adding another dependency), you can do something like this:

final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();

and then, somewhere in your code:

var token = await _firebaseMessaging.getToken();
print("Instance ID: $token");

Update

When you call get token, you get something in the following format: NNNNNNN:MMMMMMMMMMMMMMMMMM. Take only the first part before the colon (NNNNNNNN) - this is the instance ID you need to test your In-App Messaging campaign.

You can run this in your terminal.

adb logcat | grep 'InAppMessaging'

02-26 23:47:44.835 28379 28379 I FIAM.Headless: Starting InAppMessaging runtime with Installation ID dTEmOkEwRzC_xiO8YNPXs0

To retrieve the FirebaseInstanceId you need to implement the Firebase In-App messaging SDK and make sure your app connects to Firebase.

Once the app is connected to Firebase it will add the FirebaseInstanceId to the Android log once the App is run.

In the article you linked Google explains that you can find the FirebaseInstanceId by looking in the log for the string I/FIAM.Headless: Starting InAppMessaging runtime with Instance ID <YOUR_APP_ID>.

If you are using Android Studio you should be able to use the logcat window to browse the logs of the device (while debugging the App). The logcat window will also allow you to search and filter the logs so it should be relative easy to find the mentioned string.

So in short (in Android Studio):

1. Implement the Firebase In-App messaging SDK in your App;
2. Start debugging the App (preferably on a real Android device);
3. While debugging open the Logcat window;
4. Search the logs for the string I/FIAM.Headless: Starting InAppMessaging runtime with Instance ID;
5. The FirebaseInstanceId should be listed directly after the string.

Using flutterfire_installations, you can get:

• Installation ID:

  String id = await FirebaseAppInstallations.instance.getId(); 
  

• Authentication token:

  String token = await FirebaseAppInstallations.instance.getToken();