获取文档 Cloud Firestore 的字段（Android Studio-Kotlin）

Question

当我查询用户的昵称时，我可以读取昵称，但我无法从查询中取出具有正确昵称的变量。

//Get data from login user (authentication user)
val user = Firebase.auth.currentUser

//Get his mail
val mail = user?.email.toString()

//Do query to get nickname (from users collection with user's mail)
val usuaris = db.collection("usuaris")
val query = usuaris.whereEqualTo("mail", mail).get()
                .addOnSuccessListener {
                        document ->
                    if (document != null){
                     //save document to val usuari
                     val usuari = document.toObjects(Usuari::class.java)
                     //save string nickname to usuariStr
                     usuariStr = usuari[0].nickname
                     //the log show the correct nickname
                     Log.i("usuari_query",usuariStr)
                    }
                }
                .addOnFailureListener { exception ->
                    Log.w(TAG, "Error getting documents: ", exception)
}

//The usuariStr= "" is deleted when exit from query, and I can't read nickname

//dataclass to get nickname from query
data class Usuari(var adreca: String = "", var cognoms: String ="", var contrasenya:String="",
                  var mail: String="", var nickname: String="", var nom: String="",
                  var poblacio: String="", var telefon:String="")

Answer 1

这段代码是正确的，解决方案是在 .addOnSuccessListener 里面放一个函数来做更新、插入或操作结果。