kotlin - 每当 Recyclerview 行中的文本在 Kotlin 中更改时，是否有办法更改 MainActivity 中的 textview 文本

Question

我试图做一个简单的应用程序，我在其中使用 RecyclerView .
这是我的文件。

MainActivity.kt

activity_main.xml --> 其中有 RecyclerView (recyclerViewMain) single_row.xml --> recyclerViewMain 的单行
MainAdapter.kt --> 所有绑定(bind)， ViewHolder和膨胀

我也有 Product.kt --> 产品型号

现在，这就是我想要做的。

我在 itemUnit 的侧面添加了加号和减号按钮，每当我单击这些项目时，它都会完成我想要的工作，增加 itemUnit 并最终增加 itemAmount

但是，这只发生在行上，它不会更改 TextView 中的小计 ( main_activity.xml )文件。

有没有办法改变 main_activity textView每当 textView在 Recyclerview 的行中更改(或每当按钮单击该行时)？

我在这里编辑代码。 Sub Total在我单击一个项目按钮(格兰诺拉麦片、布朗尼等)之前，金额不会改变。只有在我点击这些项目后 Sub Total更改并给出更新的金额。

接口(interface)解决方案对我不起作用，我想我无法正确实现。

这是代码；

class MainActivity : AppCompatActivity(), ItemChangeListener {
override var subTotalAmnt: Double = 30.0
//override var subTotalAmount: Double = 50.0

//override fun onItemPriceChange(20.0)

lateinit var mRecyclerView : RecyclerView
private lateinit var sDatabase: DatabaseReference
var trId: Long = 0

var discAmnt : Double = 0.00

var unt = 1

var tr :Trans ?= null

var sb = 0.00
var disc = sb*.1
var tt = sb-disc

var list = ArrayList<Product>()


override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main2)

    //var subto = findViewById(R.id.txtSubAmount) as TextView


   onItemPriceChange(20.0)
    txtSubAmount.text = subTotalAmnt.toString()

    sDatabase = FirebaseDatabase.getInstance().getReference().child("Sales")

    sDatabase.child("Sales").addValueEventListener(object:ValueEventListener{
        override fun onCancelled(p0: DatabaseError) {

        }

        override fun onDataChange(p0: DataSnapshot) {
            if(p0.exists()) {
                trId = p0.childrenCount
                println(trId)
            }
        }
    })
    mRecyclerView = findViewById(R.id.recyclerView_main)
    mRecyclerView.layoutManager = LinearLayoutManager(this)
    mRecyclerView.adapter = MainAdapter(this, list)

和我的适配器类；

class MainAdapter(val context: Context, val items : List<Product>) : RecyclerView.Adapter<MainAdapter.PartViewHolder>() {
override fun onBindViewHolder(p0: MainAdapter.PartViewHolder, p1: Int) {
    p0.bindItems(items[p1])
}


 var itemListener: ItemChangeListener? = null
fun setListener(listener: ItemChangeListener) {
    this.itemListener = listener
}

override fun getItemId(position: Int): Long {
    return super.getItemId(position)
}


override fun getItemCount(): Int {
    return items.size
}

// Inflates the item views
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PartViewHolder {


    // LayoutInflater: takes ID from layout defined in XML.
    // Instantiates the layout XML into corresponding View objects.
    // Use context from main app -> also supplies theme layout values!
    val inflater = LayoutInflater.from(parent.context)
    // Inflate XML. Last parameter: don't immediately attach new view to the parent view group
    val view = inflater.inflate(R.layout.sinlge_row, parent, false)

    return PartViewHolder(view)

}


// Binds each product in the ArrayList to a view


inner class PartViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {


    // Holds the TextView that will add each product to


    fun bindItems(prd: Product) {
        val textViewName = itemView.txtOrderNumber
        var textViewUnit = itemView.txtItemUnit
        val textViewPrice = itemView.txtItemPrice
        val textViewAmount = itemView.txtItemAmount


        var id = adapterPosition

        var unitN: Int = 1
        textViewName.text = prd.pName
        textViewUnit.text = prd.pUnit.toString()
        textViewPrice.text = prd.pPrice.toString()
        var itemPrice = prd.pPrice
        var itemAmount = itemPrice.times(unitN)
        textViewAmount.text = itemAmount.toString()

        itemView.btnPlus.setOnClickListener {

            println("item id : " + id)



            //itemListener = ItemChangeListener
            itemListener?.onItemPriceChange(10.0)

            // increase the Product model single unit
            prd.pUnit = unitN++

            // println("Here is the " +MainActivity().list.get(id))

            // bind txtItemUnit from single_row to changed unitN (single unit)
            textViewUnit.text = unitN.toString()

            // change the Product model single pAmount
            prd.pAmount = prd.pPrice.times(unitN)

            // bind txtItemAmount from single_row to Product pAmount
            textViewAmount.text = prd.pAmount.toString()

            //txtSubAmount.txt =

            //MainActivity().doSomething(subTotalAmount)


        }

        itemView.btnMinus.setOnClickListener(View.OnClickListener {

            if (unitN >= 1) {
                prd.pUnit = unitN--
                println(prd.pUnit)
                textViewUnit.text = unitN.toString()

                textViewAmount.text = prd.pPrice.times(unitN).toString()
            } else
                prd.pUnit = 1
            textViewUnit.text = prd.pUnit.toString()
            textViewAmount.text = prd.pPrice.times(prd.pUnit).toString()
        })


    }


}
}

和，接口(interface)

interface ItemChangeListener {

var subTotalAmnt : Double

fun onItemPriceChange(subTotalAmount : Double){

    this.subTotalAmnt = subTotalAmount
    println("onItemPriceChange "+subTotalAmnt)

}
}

我对这个可怕的解释感到抱歉，因为我不是本地人，但愿意解释更多以寻求帮助。

亲切的问候。

编辑 MainAdapter

class MainAdapter(val context: Context, val items : List<Product>) : RecyclerView.Adapter<MainAdapter.PartViewHolder>() {
override fun onBindViewHolder(p0: MainAdapter.PartViewHolder, p1: Int) {
    p0.bindItems(items[p1])
}


lateinit var itemListener: ItemChangeListener
fun setListener(listener: ItemChangeListener) {
    this.itemListener = listener
}

override fun getItemId(position: Int): Long {
    return super.getItemId(position)
}


override fun getItemCount(): Int {
    return items.size
}

// Inflates the item views
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): PartViewHolder {


    // LayoutInflater: takes ID from layout defined in XML.
    // Instantiates the layout XML into corresponding View objects.
    // Use context from main app -> also supplies theme layout values!
    val inflater = LayoutInflater.from(parent.context)
    // Inflate XML. Last parameter: don't immediately attach new view to the parent view group
    val view = inflater.inflate(R.layout.sinlge_row, parent, false)

    return PartViewHolder(view)

}


// Binds each product in the ArrayList to a view


inner class PartViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {


    // Holds the TextView that will add each product to


    fun bindItems(prd: Product) {
        val textViewName = itemView.txtOrderNumber
        var textViewUnit = itemView.txtItemUnit
        val textViewPrice = itemView.txtItemPrice
        val textViewAmount = itemView.txtItemAmount


        var id = adapterPosition

        var unitN: Int = 1
        textViewName.text = prd.pName
        textViewUnit.text = prd.pUnit.toString()
        textViewPrice.text = prd.pPrice.toString()
        var itemPrice = prd.pPrice
        var itemAmount = itemPrice.times(unitN)
        textViewAmount.text = itemAmount.toString()

        itemView.btnPlus.setOnClickListener {

            println("item id : " + id)


            //itemListener = ItemChangeListener
            itemListener.onItemPriceChange(20.0)
            // increase the Product model single unit
            prd.pUnit = unitN++

            // println("Here is the " +MainActivity().list.get(id))

            // bind txtItemUnit from single_row to changed unitN (single unit)
            textViewUnit.text = unitN.toString()

            // change the Product model single pAmount
            prd.pAmount = prd.pPrice.times(unitN)

            // bind txtItemAmount from single_row to Product pAmount
            textViewAmount.text = prd.pAmount.toString()

            //txtSubAmount.txt =

            //MainActivity().doSomething(subTotalAmount)


        }

        itemView.btnMinus.setOnClickListener(View.OnClickListener {

            if (unitN >= 1) {
                prd.pUnit = unitN--
                println(prd.pUnit)
                textViewUnit.text = unitN.toString()

                textViewAmount.text = prd.pPrice.times(unitN).toString()
            } else
                prd.pUnit = 1
            textViewUnit.text = prd.pUnit.toString()
            textViewAmount.text = prd.pPrice.times(prd.pUnit).toString()
        })


    }


}
 }

Answer 1

我认为你可以使用 接口(interface) .

首先，您创建接口(interface)定义(在单独的文件或适配器中)。
-- 例如: interface ItemChangeListener { fun onItemPriceChange(传递 itemprice 或 totalprice) }

接下来在适配器

中创建一个监听器对象

点赞 lateinit var 监听器:ItemChangeListener 内部适配器(使用 设置 fun setListener(listener:ItemChangeListener){//代码 } )。

让主要事件实现接口(interface)。

通过 mainActivity 这个到适配器.setListener

点击按钮，可以调用 listener.onItemPriceChange(pass itemprice or totalprice)

您可以通过这种方式获取主要事件的参数。

检查此 link一些细节..我猜也可以使用构造函数参数来完成。