需要帮助解决 Android Studio 中的 Firebase 查询

Question

I'm trying to see if this "employee" has a service where the serviceComplete field is false (in other words trying to see if this employee has an active service that is not complete) if a Toast message pops up letting the employee know he cannot accept more services has he has an active one. If not the employee should be able to accept the service.

My problem is no matter what I do this firebase query seems to think there are documents in my DB that do not exist . Every time I go to accept the service it displays the toast. Meaning there is a collection "services" where a document has the field "serviceCompleted" which is equal to "false" but in my DB there is no collection "services" under employees

My database showing no collection "services" exist underneath "employees"

and here is my Kotlin code

fun setButton(serviceID: String, eID: String){

        val btnAcceptService = view.findViewById<Button>(R.id.btnAcceptService)
        btnAcceptService.setOnClickListener {
            val queryEmpServices = database.collection("employees").document(eID).collection("services").whereEqualTo("serviceComplete", false)

            queryEmpServices.get().addOnSuccessListener { documents ->

                if (documents != null){
                    Toast.makeText(applicationContext,"You already have a service active!", Toast.LENGTH_SHORT).show()

                }else {

                    database.collection("services").document(serviceID).update("saccept", true).addOnSuccessListener {

                        database.collection("services").document(serviceID).get().addOnSuccessListener { document ->

                            if (document != null) {

                                val Location = document.get("ulocation").toString()
                                val serviceType = document.get("serviceType").toString()
                                val uComment = document.get("ucomment").toString()
                                val uID = document.get("uid").toString()

                                if (document.getBoolean("saccept") == true) {

                                    database.collection("users").document(document.get("uid").toString()).collection("services").document(serviceID).update("saccept", true).addOnSuccessListener {

                                        database.collection("employees").document(mAuth.currentUser!!.uid).get().addOnSuccessListener { document ->

                                            if (document != null) {

                                                val calendar = Calendar.getInstance()
                                                val simpleDateFormat = SimpleDateFormat("dd-MM-yyyy HH:mm:ss")
                                                val acceptDate = simpleDateFormat.format(calendar.time)

                                                val eFullName = document.get("ename").toString() + " " + document.get("esurname").toString()
                                                val eCompany = document.get("ecompany").toString()

                                                database.collection("users").document(uID).get().addOnSuccessListener { document ->


                                                    val uName = document.get("name").toString()
                                                    val uPhonenumber = document.get("phonenumber").toString()
                                                    val serviceAccept = EmployeeServiceAccept(acceptDate, serviceID, Location, serviceType, uComment, uName, uPhonenumber, false)

                                                    database.collection("employees").document(mAuth.currentUser!!.uid).collection("acceptedservices").document(serviceID).set(serviceAccept)
                                                    database.collection("services").document(serviceID).update("acceptedby", eFullName + ", " + eCompany)
                                                    database.collection("users").document(uID).collection("services").document(serviceID).update("acceptedby", eFullName + ", " + eCompany)
                                                    Toast.makeText(applicationContext, "Service Accepted", Toast.LENGTH_SHORT).show()



                                                }


                                            }


                                        }


                                    }


                                }

                            } else {

                                Toast.makeText(applicationContext, "Failed to accept service", Toast.LENGTH_SHORT).show()

                            }

Answer 1

When you are using the Task.addOnSuccessListener(OnSuccessListener) method on a Query object, the result that you get can be a success or a failure, never both and never null. It will always be one, or the other.

That being said, you should never check the documents object against nullity because it can never be null. What you should do instead, is to check the "documents" object, which is of type QuerySnapshot to see if isEmpty() or not:

if (!documents.isEmpty){
    Toast.makeText(applicationContext,"You already have a service active!", Toast.LENGTH_SHORT).show()
} else {
    Toast.makeText(applicationContext,"You don't have a service active!", Toast.LENGTH_SHORT).show()
}

Where indeed the Toast message from the "else" part of the statement will be displayed, as there are no documents present in the QuerySnapshot object:

"You don't have a service active!"