is there a way to change the textview text in the MainActivity whenever the text in recyclerview row changed in Kotlin - kotlin

Question

I an trying to do a simple app, in which I use RecyclerView.
Here are my files.
MainActivity.kt
activity_main.xml --> which has RecyclerView (recylerViewMain)
single_row.xml --> single row for recyclerViewMain
MainAdapter.kt --> where all bindings , ViewHolder and inflating
I have also
Product.kt --> model for Products
Now, here what i am trying to do.
I have added Plus and Minus buttons on the side of itemUnit and whenever i click those items it does the job i wanted, increasing the itemUnit and eventually, itemAmount
However, this happens only on Row, and it doesn't change the Sub Total (TextView) in main_activity.xml file.
Is there a way to change the main_activity textView whenever textView in the Row of Recyclerview changes (or whenever button clicked on the row) ?
I am editing the code here.
Sub Total amount doesn't change until I click an item button (Granola, Brownie etc.). Only after I click the these items Sub Total changes and gives the updated amount.
the interface solution didnt work for me, I think I couldnt implement it right.
here are the codes ;
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)
and my Adapter Class;
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()
})
}
}
}
and, Interface
interface ItemChangeListener {
var subTotalAmnt : Double
fun onItemPriceChange(subTotalAmount : Double){
this.subTotalAmnt = subTotalAmount
println("onItemPriceChange "+subTotalAmnt)
}
}
I am sorry for this terrible explanation as I am not native, but willing to explain more for help.
Kind Regards.
Edited 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

I think you can do it using interface.
First you create interface definition (in a separate file or in adapter).
-- for eg: interface ItemChangeListener { fun onItemPriceChange(pass itemprice or totalprice) }
next you create an object of listener inside adapter
Like lateinit var listener: ItemChangeListener inside adapter (set using fun setListener(listener:ItemChangeListener){ // code } ).
Let the main activity implement the interface.
pass the mainActivity this to the adapter.setListener
on Clicking the button, you can call listener.onItemPriceChange(pass itemprice or totalprice)
you can get the parameter on main activity in this way.
Check this link for some details.. Same can be done using constructor parameter I guess.