如何根据从 Firebase 数据库中检索到的值更新 textview答案

【问题标题】：How to update textview depending on retrieved value from Firebase Database如何根据从 Firebase 数据库中检索到的值更新 textview
【发布时间】：2022-01-18 01:00:00
【问题描述】：

我以前问过这个问题，但我没有得到任何答案。我正在尝试根据从我的 firebase 数据库中检索到的另外两个文本视图的结果来更新文本视图。

我从这个代码块中获取收入

incomeSumReference.addValueEventListener(object : ValueEventListener {
            @SuppressLint("SetTextI18n")
            @RequiresApi(Build.VERSION_CODES.N)
            override fun onDataChange(snapshot: DataSnapshot) {
                var sum = 0.0

                for (dataSnapshot in snapshot.children) {
                    val map = dataSnapshot.getValue() as Map<*, *>
                    val sumOfIncomes = map.get("itemValue")
                    val sumo = sumOfIncomes.toString()
                    val sumAsDouble: Double = sumo.toDouble()
                    sum += sumAsDouble
                    val stringSum = sum.toString()
                    incomeSumToFormated = formatNumberString(stringSum)
                    profitTextView.text = "+$" + incomeSumToFormated.toString()

                }


            }
            override fun onCancelled(error: DatabaseError) {

            }
        })

这是用于检索花费的代码块

val spentSumReference = database.getReference("users").child(uid).child("Expenses").child(
            currentYear.toString()
        ).child(currentMonthInString.toString())
        spentSumReference.addValueEventListener(object : ValueEventListener {
            @RequiresApi(Build.VERSION_CODES.N)
            override fun onDataChange(snapshot: DataSnapshot) {
                var sum = 0.0

                for (dataSnapshot in snapshot.children) {
                    var map = dataSnapshot.getValue() as Map<String, Object>
                    val sumOfIncomes = map.get("itemValue")
                    var sumo = sumOfIncomes.toString()
                    var sumAsDouble: Double? = sumo.toDouble()
                    sum += sumAsDouble!!

                    var stringSum = sum.toString()
                    var spentSumToFormated =
                        formatNumberString(stringSum) // this is what I want to get outside

                    spentTextView.text = "-$" + spentSumToFormated.toString()
                }
                countExecutedMethods++
            }

            override fun onCancelled(error: DatabaseError) {

            }

        })

我想让我的 balanceTextView 显示收入和花费的差异。但我不能这样做，因为最初它们被设置为 null。

运行代码之前

fun getBalance(){
  val total = income-spent
  balanceTextView.text = "$total"
}

我必须确保从 firebase 检索数据的函数 getIncome() 和 getExpense() 已经执行。我尝试了很多方法，但并不幸运。最好的方法是什么？

【问题讨论】：

你试过使用嵌套监听器吗？
您是否建议不要创建两个函数 getExpense() 和 getIncome()，而是创建一个函数，例如：getCurrentMonthData，并使用嵌套侦听器获取所需数据并在它们下尝试 getBalance() 函数？ @AlexMamo
是的，完全正确。试一试，告诉我它有效。
我完全按照你说的做了。它现在似乎工作得很好。我将在下面发布我的答案，您可以查看。 @AlexMamo

标签： android database firebase kotlin firebase-realtime-database

【解决方案1】：

所以正如@AlexMamo 建议的那样，我使用了嵌套侦听器并想出了下面的代码。它似乎正在工作。如果我以后遇到任何错误，我会确保更新我的答案。

val getMonthDataReference = database.getReference("users").child(uid)
        getMonthDataReference.addValueEventListener(object : ValueEventListener{
            override fun onDataChange(snapshot: DataSnapshot) {

            var total = 0.0
                val incomeMoneyQuery = getMonthDataReference.child("Incomes").child(currentYear.toString()).child(currentMonthInString.toString())
                incomeMoneyQuery.addValueEventListener(object : ValueEventListener{
                    @RequiresApi(Build.VERSION_CODES.N)
                    override fun onDataChange(snapshot: DataSnapshot) {
                        var sumOfIncome = 0.0
                            for (dataSnapshot in snapshot.children) {
                                val map = dataSnapshot.getValue() as Map<*, *>
                                val sumOfIncomes = map.get("itemValue")
                                val sumo = sumOfIncomes.toString()
                                val sumAsDouble: Double = sumo.toDouble()
                                sumOfIncome += sumAsDouble
                                val stringSum = sumOfIncome.toString()
                                var incomeSumToFormated = formatNumberString(stringSum)
                                incomeTextView!!.text = "+$" + incomeSumToFormated.toString()
                            }
                        total+=sumOfIncome
                        var totalFormated = formatNumberString(total.toString())
                        balance!!.text ="$$totalFormated"
                    }
                    override fun onCancelled(error: DatabaseError) {
                    }
                })
                val spentMoneyQuery = getMonthDataReference.child("Expenses").child(currentYear.toString()).child(currentMonthInString.toString())
                spentMoneyQuery.addValueEventListener(object : ValueEventListener{

                    @RequiresApi(Build.VERSION_CODES.N)
                    override fun onDataChange(snapshot: DataSnapshot) {
                        var sumOfSpent = 0.0
                        for (dataSnapshot in snapshot.children) {
                            var map = dataSnapshot.getValue() as Map<String, Object>
                            val sumOfIncomes = map.get("itemValue")
                            var sumo = sumOfIncomes.toString()
                            var sumAsDouble: Double? = sumo.toDouble()
                            sumOfSpent += sumAsDouble!!

                            var stringSum = sumOfSpent.toString()

                            var spentSumToFormated = formatNumberString(stringSum)
                            spentMoneyText!!.text = "-$" + spentSumToFormated.toString()

                        }
                        total-=sumOfSpent
                        var totalFormated = formatNumberString(total.toString())
                        balance!!.text ="$$totalFormated"

                    }

                    override fun onCancelled(error: DatabaseError) {

                    }

                })

            }
            override fun onCancelled(error: DatabaseError) {
            }
        })
al getMonthDataReference = database.getReference("users").child(uid)
        getMonthDataReference.addValueEventListener(object : ValueEventListener{
            override fun onDataChange(snapshot: DataSnapshot) {

            var total = 0.0
                val incomeMoneyQuery = getMonthDataReference.child("Incomes").child(currentYear.toString()).child(currentMonthInString.toString())
                incomeMoneyQuery.addValueEventListener(object : ValueEventListener{
                    @RequiresApi(Build.VERSION_CODES.N)
                    override fun onDataChange(snapshot: DataSnapshot) {
                        var sumOfIncome = 0.0
                            for (dataSnapshot in snapshot.children) {
                                val map = dataSnapshot.getValue() as Map<*, *>
                                val sumOfIncomes = map.get("itemValue")
                                val sumo = sumOfIncomes.toString()
                                val sumAsDouble: Double = sumo.toDouble()
                                sumOfIncome += sumAsDouble
                                val stringSum = sumOfIncome.toString()
                                var incomeSumToFormated = formatNumberString(stringSum)
                                incomeTextView!!.text = "+$" + incomeSumToFormated.toString()
                            }
                        total+=sumOfIncome
                        var totalFormated = formatNumberString(total.toString())
                        balance!!.text ="$$totalFormated"
                    }
                    override fun onCancelled(error: DatabaseError) {
                    }
                })
                val spentMoneyQuery = getMonthDataReference.child("Expenses").child(currentYear.toString()).child(currentMonthInString.toString())
                spentMoneyQuery.addValueEventListener(object : ValueEventListener{

                    @RequiresApi(Build.VERSION_CODES.N)
                    override fun onDataChange(snapshot: DataSnapshot) {
                        var sumOfSpent = 0.0
                        for (dataSnapshot in snapshot.children) {
                            var map = dataSnapshot.getValue() as Map<String, Object>
                            val sumOfIncomes = map.get("itemValue")
                            var sumo = sumOfIncomes.toString()
                            var sumAsDouble: Double? = sumo.toDouble()
                            sumOfSpent += sumAsDouble!!

                            var stringSum = sumOfSpent.toString()

                            var spentSumToFormated = formatNumberString(stringSum)
                            spentMoneyText!!.text = "-$" + spentSumToFormated.toString()

                        }
                        total-=sumOfSpent
                        var totalFormated = formatNumberString(total.toString())
                        balance!!.text ="$$totalFormated"

                    }

                    override fun onCancelled(error: DatabaseError) {

                    }

                })

            }
            override fun onCancelled(error: DatabaseError) {
            }
        })

【讨论】：