Firebase cloud function is still public after appcheck enforced

I have a Flutter mobile app (no web). I want the getData function to be accessed by my app only. When I did not have any app check the function was accessible through any web browser because it was public.

After I enable appcheck and add the following code. The app cloud function is still accessible like before publically.

How do I fix this?

import * as functions from "firebase-functions";
import * as admin from "firebase-admin";

admin.initializeApp();


exports.getData = functions
    .runWith({
        enforceAppCheck: true, 
    })
    .https.onRequest(async (request, response) => {

At the time of writing, Firebase App Check can be used with:

App Check currently works with the following Firebase products:

• Realtime Database
• Cloud Firestore
• Cloud Storage
• Cloud Functions (callable functions)
• Authentication (beta; requires upgrade to Firebase Authentication with Identity Platform)

In your code, you define a HTTPS Request Cloud Function, which is not a Callable Cloud Function.

To use App Check, you will need to redefine your function as a Callable Cloud Function:

exports.getData = functions
    .runWith({
        enforceAppCheck: true, 
    })
    .https.onCall(async (data, context) => {
        return { /* ... response data ... */ }; 
    });

Then on your client, you would call it using:

try {
  final result =
      await FirebaseFunctions.instance.httpsCallable('addMessage').call();
  // do something with result
} on FirebaseFunctionsException catch (error) {
  print(error.code);
  print(error.details);
  print(error.message);
}