Receiving data from calling Firebase Cloud Function in Android

Question

I'm trying to calling a firebase cloud function that I have written.

I have tested the function using Postman to mimic HTTP requests. Here is the JSON result when I call my function within Postman:

{
 "groups": [
    {
        "isPublic": true,
        "members": [
            true
        ],
        "numberOfMembers": 1,
        "groupId": "-LAOPAzMGzOd9qULPxue"
    },
    {
        "isPublic": true,
        "members": [
            true
        ],
        "numberOfMembers": 1,
        "groupId": "-LAOP7ISDI2JPzAgTYGi"
    }
 ]
}

I am attempting to do the same and retrieve this JSON list within my android app. I am following the example on Firebase's website : https://firebase.google.com/docs/functions/callable

This is Firebase's example on how to retrieve the data:

return mFunctions
        .getHttpsCallable("addMessage")
        .call(data)
        .continueWith(new Continuation<HttpsCallableResult, String>() {
            @Override
            public String then(@NonNull Task<HttpsCallableResult> task) throws Exception {
                String result = (String) task.getResult().getData();
                return result;
            }
        });

It is unclear how I can take the result from my cloud function and use it in the rest of my Android app.

Furthermore, this example returns a Task object which according to Firebase's documentation has now deprecated : https://firebase.google.com/docs/reference/admin/java/reference/com/google/firebase/tasks/Task )

Is there a clearer, more simple way to handle the data from a function call?

Calling a function is extremely simple so I feel that there must be a more straight forward method to receiving the response.

Answer 1

If you're simply interested in getting JSON from your endpoint, do this from your Activity:

        mFunctions
            .getHttpsCallable("getGroups") //Whatever your endpoint is called
            .call()
            .addOnSuccessListener(this, new OnSuccessListener<HttpsCallableResult>() {
                @Override
                public void onSuccess(HttpsCallableResult httpsCallableResult) {
                    try{
                        Gson g = new Gson();
                        String json = g.toJson(httpsCallableResult.getData());
                        Groups groups = g.fromJson(json,Groups.class);
                    } catch (Exception e){
                        Log.d("Error",e.toString());
                    }
                }
            });

Answer 2

If you're using Kotlinx Serialization, you can use org.json.JsonElement to convert the result data into a format that the serialization framework will accept:

val json = Json(JsonConfiguration.Stable)

fun getPerson(personId: String): Task<Person> {
    val function = functions.getHttpsCallable("getPersonInfo")

    return function.call(mapOf("personId" to personId)).continueWith { task ->
        val result = task.result ?: throw Exception("result is null")

        val jsonString = org.json.JSONObject(result.data as Map<*, *>).toString()
        json.parse(Person.serializer(), jsonString)
    }
}