我是 Kotlin 语言的新手。任何人都可以帮助如何添加显示在不同 onClickListener 上的两个总值吗？

var addQuantity = 0     // counter variable

 // button_two on clickListener 
button_two.setOnClickListener{                                     
    val laptopTwo = 500.60
    val total_price_two: Double
    addQuantity = addQuantity + 1
    total_price_two = (addQuantity * laptopTwo).toDouble()
    resultDisplayText.text = total_price_two.toString()       //displays the result in TextView
}

 // button_three on clickListener 
button_three.setOnClickListener {
    val laptopThree=400.00
    val total_price_three:Double
    addQuantity = addQuantity + 1
    total_price_three =( addQuantity * laptopThree).toDouble()
    resultDisplayText.text=total_price_three.toString() //displays the result in TextView 
}

//submit button on clickListener
submit.setOnClickListener {                                              
    val total: Double
    total = total_price_three + total_price_two // get an error here....
}

每次我点击button_two和button_three，它都会增加数量并给出数量的总价。现在我想在点击提交按钮时显示总价，但它不起作用。谁能帮我解决这个问题。