Using .addOnSuccessListener to return a value for a private method

Issue

Good day. Is there some way that I could implement this one?

val db = Firebase.firestore
        val userID = Firebase.auth.currentUser!!.uid
        val infoRef = db.collection("user").document(userID).collection("profile").document("info")
        infoRef.get()
            .addOnSuccessListener {document ->
                if(document != null){
                    //get the data as cast to hashmap
                    val data = document.data as HashMap<*, *>
                    //get the username field and set text for greet user as the same value inside firestore
                    val username = data["username"] as String
                    tv_greet_user.text = "Hello, $username"
                }
            }

//extract the code above as a new method called "getUsername()"

val username : String = getUsername()

tv_greet_user.text = "Hello, $username"

Solution

Yes, you can create a function that looks like this:

fun getUsername(data: HashMap<String, Any>) = data["username"] as String

And inside your callback simply call:

val username = getUsername(data)

Is there a way to extract the whole block into a separate method? So that in the onCreate method, I could simply change the TextView into something like: val username = getUsername() tv_greet_user.text = "Hello, $username"

Edit:

As also Frank van Puffelen mentioned in his you cannot return the result of an asynchronous operation as a result of a method. Since you are using Kotlin programming, please note that there is actually o solution. I wrote an article called:

• How to read data from Cloud Firestore using get()?

In which I explained four ways in which you can get data from Firestore. So if you are willing to use Kotlin Coroutines, then things will be much simpler.

Answered By - Alex Mamo