Passing data from an activity (On Button clicked), to be added to a recyclerView adapter at another activity, without starting the activity

Question

I'm trying to make a food application with android-Kotlin, and it contains: The problem is i tried many times to send data from "PopularDetailedActivity" to another activity onClick (Add To Cart Button) which contains my Cart or basket that i choose, but i can't access a solution.

PopularAdapter.kt that pass the data to PopularDetailedActivity.kt

class PopularAdapter(private var popItems: List<Popular>): RecyclerView.Adapter<PopularAdapter.MyViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val popView = LayoutInflater.from(parent.context).inflate(R.layout.pop_items, parent, false)
        return MyViewHolder(popView)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        val newPop: Popular = popItems[position]
        holder.foodName.text = newPop.foodName
        holder.foodImg.setImageResource(newPop.foodImage)
        holder.foodDollar.text = newPop.foodDollar
        holder.foodPrice.text = newPop.foodPrice.toString()
        holder.foodDetails.text = newPop.foodDetails
        holder.myPop = newPop
    }

    override fun getItemCount(): Int {
        return popItems.size
    }
    fun submitList(categories: List<Popular>){
        popItems = categories
    }
    class MyViewHolder constructor(itemView: View, var myPop: Popular?= null):
        RecyclerView.ViewHolder(itemView){
        init {
            itemView.addBtn.setOnClickListener {
                val myIntent = Intent(itemView.context, PopularDetailed::class.java)
                myIntent.putExtra("title", myPop!!.foodName)
                myIntent.putExtra("price", myPop!!.foodPrice)
                myIntent.putExtra("img", myPop!!.foodImage)
                myIntent.putExtra("description", myPop!!.foodDetails)
                itemView.context.startActivity(myIntent)
            }
        }
        val foodName: TextView = itemView.popMainText
        val foodImg: ShapeableImageView = itemView.popMainImg
        val foodDollar: TextView = itemView.dollarTxt
        val foodPrice: TextView = itemView.priceValue
        val foodDetails: TextView = itemView.popDetail
    }
}

PopularDetailedActivity.kt

class PopularDetailed : AppCompatActivity() {
    private lateinit var cTitle: TextView
    private lateinit var cImage: ShapeableImageView
    private lateinit var cPrice: TextView
    private lateinit var cDollar: TextView
    private lateinit var cMinus: ImageView
    private lateinit var cPlus: ImageView
    private lateinit var cItemVal: TextView
    private lateinit var cDescription: TextView
    private lateinit var cAddBtn: Button
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_popular_details)
        val bundle = intent.extras
        val localTitle = bundle!!.getString("title")
        val localPrice = bundle.getDouble("price")
        val localImage = bundle.getInt("img")
        val localDescription = bundle.getString("description")
        initValues()
        cTitle.text = localTitle
        cPrice.text = localPrice.toString()
        cImage.setImageResource(localImage)
        cDescription.text = localDescription
        
        incDecNum()
        
        cAddBtn.setOnClickListener {
            if (incDecValue.text.toString().toInt() > 0){
                Toast.makeText(applicationContext, "Added To Your Cart", Toast.LENGTH_SHORT).show()
            }
        }
    }
    //Initiate Values
    private fun initValues(){
        cTitle = findViewById(R.id.pop_local_title)
        cImage = findViewById(R.id.pop_local_img)
        cPrice = findViewById(R.id.localPriceValue)
        cDollar = findViewById(R.id.localDollarTxt)
        cPlus = findViewById(R.id.incNum)
        cItemVal = findViewById(R.id.incDecValue)
        cMinus = findViewById(R.id.decNum)
        cDescription = findViewById(R.id.pop_local_des)
        cAddBtn = findViewById(R.id.local_add_btn)
    }
    //Increase or decrease items' number
    private fun incDecNum(){
        
        val priceValueInString = localPriceValue.toString()
        var priceInDouble = priceValueInString.split("")[0].toDoubleOrNull()
        
        val incDecValueInString = incDecValue.toString()
        var numberOfItems = incDecValueInString.split(" ")[0].toIntOrNull()
        numberOfItems = 0
        decNum.setOnClickListener {
            if (numberOfItems > 0){
                numberOfItems -= 1
                val newVal = numberOfItems.toString()
                incDecValue.text = newVal
                //Changing the price
                /*if (priceInDouble != null) {
                    if (newVal > 0.toString()){
                        priceInDouble -= priceInDouble
                        localPriceValue.text = priceInDouble.toString()
                    }
                }*/
            } else{
                //Toast.makeText(applicationContext, "", Toast.LENGTH_SHORT).show()
            }
        }
        incNum.setOnClickListener {
            numberOfItems += 1
            val newVal = numberOfItems.toString()
            incDecValue.text = newVal
            //Changing the price
            /*if (priceInDouble != null) {
                if (newVal > 1.toString()){
                    priceInDouble += priceInDouble
                    localPriceValue.text = priceInDouble.toString()
                }
            }*/
        }
    }
}

MyCartBasketActivity.kt

class MyCartBasket : AppCompatActivity() {
    private val myCartItems = ArrayList<MyCart>()
    private val myCartAdapter = MyCartAdapter(myCartItems)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_my_cart_basket)
        myCartDynamic.layoutManager = LinearLayoutManager(applicationContext, RecyclerView.VERTICAL, false)
        myCartDynamic.adapter = myCartAdapter
    }
    //Adding Data
    /*private fun addData(){
        val cartItems = MyCartDynamicDataSource.createDynamicCartItems(myCartItems)
        myCartAdapter.submitList(cartItems)
    }*/
}

MyCartAdapter.kt for the result activity at MyCartBasketActivity.kt

class MyCartAdapter(private var cartItems: List<MyCart>):
    RecyclerView.Adapter<MyCartAdapter.MyViewHolder>() {

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val cartView = LayoutInflater.from(parent.context).inflate(R.layout.my_cart_items, parent, false)
        return MyViewHolder(cartView)
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        val newCart = cartItems[position]
        holder.cartedImg.setImageResource(newCart.cartedImg)
        holder.cartedTitle.text = newCart.cartedTitle
        holder.cartedItemNum.text = newCart.cartedItemNum
        holder.cartedLPriceValue.text = newCart.cartedLPriceValue
        holder.cartedIPriceValue.text = newCart.cartedIPriceValue
        holder.cartedPlusItem.text = newCart.cartedPlusItem
        holder.cartedMinusItem.text = newCart.cartedMinusItem
    }

    fun submitList(cartNewItems: List<MyCart>){
        cartItems = cartNewItems
    }

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

    class MyViewHolder constructor(itemView: View): RecyclerView.ViewHolder(itemView){
        val cartedImg: ShapeableImageView = itemView.myCartedImg
        val cartedTitle: TextView = itemView.myCartedTitle
        val cartedItemNum: TextView = itemView.myCartItemNum
        val cartedLPriceValue: TextView = itemView.localPriceCart
        val cartedIPriceValue: TextView = itemView.localPriceCartA
        val cartedPlusItem: Button = itemView.incNumCart
        val cartedMinusItem: Button = itemView.decNumCart
    }
}

Popular.kt

class Popular {
    var foodName:String
    var foodImage:Int
    var foodDollar:String
    var foodPrice:Double
    var foodDetails:String
    constructor(foodName:String, foodImg:Int, foodDollar:String, foodPrice:Double, foodDetails:String){
        this.foodName = foodName
        this.foodImage = foodImg
        this.foodDollar = foodDollar
        this.foodPrice = foodPrice
        this.foodDetails = foodDetails
    }

activity_popular_details.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginStart="25dp"
    android:layout_marginEnd="25dp"
    tools:context=".PopularDetailed">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/pop_local_title"
        android:theme="@style/MyPopLocalText"
        android:text="@string/hello_blank_fragment"
        android:layout_marginTop="35dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/local_price"
        android:orientation="horizontal"
        android:layout_marginTop="15dp"
        app:layout_constraintTop_toBottomOf="@id/pop_local_title"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent">

        <TextView
            android:id="@+id/localDollarTxt"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/dollarSign"
            android:textColor="@android:color/holo_orange_light"
            android:textSize="16sp"
            tools:ignore="TextContrastCheck" />
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/localPriceValue"
            android:text="@string/price_val"
            android:textStyle="bold"
            android:textColor="@color/black"
            android:textSize="16sp"/>
    </LinearLayout>
    <com.google.android.material.imageview.ShapeableImageView
        android:layout_width="300dp"
        android:layout_height="350dp"
        android:id="@+id/pop_local_img"
        android:src="@drawable/hot_breakfast"
        android:layout_marginTop="5dp"
        app:layout_constraintTop_toBottomOf="@id/local_price"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/incDecItemNum"
        android:orientation="horizontal"
        app:layout_constraintTop_toBottomOf="@id/pop_local_img"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent">
        <ImageView
            android:layout_width="35dp"
            android:layout_height="35dp"
            android:id="@+id/decNum"
            android:contentDescription="@string/dollarSign"
            android:background="@drawable/inc_dec_back"
            android:src="@drawable/minus"
            tools:ignore="TouchTargetSizeCheck"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintStart_toStartOf="parent"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/incDecValue"
            android:text="@string/_0"
            android:layout_marginStart="8dp"
            android:layout_marginEnd="8dp"
            android:textSize="15sp"
            android:textStyle="bold"
            android:textColor="@color/black"
            app:layout_constraintStart_toEndOf="@id/decNum"
            app:layout_constraintTop_toTopOf="@id/decNum"
            app:layout_constraintBottom_toBottomOf="@id/decNum"/>
        <ImageView
            android:layout_width="35dp"
            android:layout_height="35dp"
            android:id="@+id/incNum"
            android:layout_marginStart="8dp"
            android:contentDescription="@string/dollarSign"
            android:background="@drawable/inc_dec_back"
            android:src="@drawable/plus"
            tools:ignore="TouchTargetSizeCheck"
            app:layout_constraintTop_toTopOf="@id/decNum"
            app:layout_constraintStart_toEndOf="@id/incDecValue"/>
    </androidx.constraintlayout.widget.ConstraintLayout>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/pop_local_des"
        android:text="@string/meal_description"
        android:layout_marginTop="10dp"
        android:theme="@style/MyPopLocalDes"
        app:layout_constraintTop_toBottomOf="@id/incDecItemNum"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/local_add_btn"
        android:backgroundTint="#FF5E00"
        android:text="@string/add_to_cart"
        android:textStyle="bold"
        android:textSize="17sp"
        app:shapeAppearanceOverlay="@style/Button5"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

activity_my_cart_basket.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MyCartBasket">

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/maiCartV"
        android:layout_marginBottom="50dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintBottom_toBottomOf="parent">
        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/myCartView"
            android:orientation="vertical"
            android:layout_marginTop="15dp"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/myCartMainText"
                android:text="@string/your_cart"
                android:theme="@style/MyHeadText"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintEnd_toEndOf="parent"/>

            <androidx.recyclerview.widget.RecyclerView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:id="@+id/myCartDynamic"
                android:layout_marginTop="15dp"/>

        </LinearLayout>

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/itemsTotalPrice"
            android:orientation="horizontal"
            android:layout_marginTop="25dp"
            app:layout_constraintTop_toBottomOf="@id/myCartView"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/totalPriceText"
                android:layout_marginStart="15dp"
                android:text="@string/items_total_price"
                android:textStyle="bold"
                android:textColor="@color/black"
                android:textSize="16sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toStartOf="parent"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/mainTotalValue"
                android:text="@string/_0"
                android:layout_marginEnd="15dp"
                android:textColor="@color/black"
                android:textSize="13sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"/>

            <TextView
                android:id="@+id/mainTotalDollar"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="5dp"
                android:text="@string/dollarSign"
                android:textColor="#FF5E00"
                android:textSize="13sp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@id/mainTotalValue"
                app:layout_constraintTop_toTopOf="parent"
                tools:ignore="TextContrastCheck" />


        </androidx.constraintlayout.widget.ConstraintLayout>
        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/itemsDeliveryPrice"
            android:orientation="horizontal"
            android:layout_marginTop="10dp"
            app:layout_constraintTop_toBottomOf="@id/itemsTotalPrice"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/totalDeliveryText"
                android:layout_marginStart="15dp"
                android:text="@string/delivery_services"
                android:textStyle="bold"
                android:textColor="@color/black"
                android:textSize="16sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toStartOf="parent"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/mainDeliveryValue"
                android:text="@string/_0"
                android:layout_marginEnd="15dp"
                android:textColor="@color/black"
                android:textSize="13sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"/>

            <TextView
                android:id="@+id/mainDeliveryDollar"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="5dp"
                android:text="@string/dollarSign"
                android:textColor="#FF5E00"
                android:textSize="13sp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@id/mainDeliveryValue"
                app:layout_constraintTop_toTopOf="parent"
                tools:ignore="TextContrastCheck" />


        </androidx.constraintlayout.widget.ConstraintLayout>
        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/itemsTaxPrice"
            android:orientation="horizontal"
            android:layout_marginTop="10dp"
            app:layout_constraintTop_toBottomOf="@id/itemsDeliveryPrice"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/totalTaxText"
                android:layout_marginStart="15dp"
                android:text="@string/taxes"
                android:textStyle="bold"
                android:textColor="@color/black"
                android:textSize="16sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toStartOf="parent"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/mainTaxValue"
                android:text="@string/_0"
                android:layout_marginEnd="15dp"
                android:textColor="@color/black"
                android:textSize="13sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"/>

            <TextView
                android:id="@+id/mainTaxDollar"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="5dp"
                android:text="@string/dollarSign"
                android:textColor="#FF5E00"
                android:textSize="13sp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@id/mainTaxValue"
                app:layout_constraintTop_toTopOf="parent"
                tools:ignore="TextContrastCheck" />


        </androidx.constraintlayout.widget.ConstraintLayout>
        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/itemsTotal"
            android:orientation="horizontal"
            android:layout_marginTop="25dp"
            app:layout_constraintTop_toBottomOf="@id/itemsTaxPrice"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent">

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/totalTotalText"
                android:layout_marginStart="15dp"
                android:text="@string/total"
                android:textStyle="bold"
                android:textColor="@color/black"
                android:textSize="25sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintStart_toStartOf="parent"/>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/mainTotalV"
                android:text="@string/_0"
                android:layout_marginEnd="15dp"
                android:textColor="@color/black"
                android:textSize="18sp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"/>

            <TextView
                android:id="@+id/mainTotalD"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginEnd="5dp"
                android:text="@string/dollarSign"
                android:textColor="#FF5E00"
                android:textSize="18sp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@id/mainTotalV"
                app:layout_constraintTop_toTopOf="parent"
                tools:ignore="TextContrastCheck" />


        </androidx.constraintlayout.widget.ConstraintLayout>

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:id="@+id/cart_check_btn"
            android:backgroundTint="#FF5E00"
            android:text="@string/checkout"
            android:textStyle="bold"
            android:textSize="25sp"
            android:layout_marginStart="50dp"
            android:layout_marginEnd="50dp"
            android:layout_marginBottom="35dp"
            app:shapeAppearanceOverlay="@style/Button5"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintEnd_toEndOf="parent"/>
    </androidx.constraintlayout.widget.ConstraintLayout>

    <include layout="@layout/bottom_bar"/>

</androidx.constraintlayout.widget.ConstraintLayout>

I want to add the data which viewed at "PopularDetailedActivity" to "MyCartActivity" without starting it, and then to the adapter of its dynamic recyclerView, and update it. But, i can't access the proper solution.

Answer 1

You need to persist basket data somehow, then pass data itself (or reference to this data) to new screen ( MyCartActivity ).

The tricky question is to how to persist the data.

IMO, good solution can be to use fragments instead of activities, then you can use sharedViewModel , where you store data with basket items. This shared view model will be accessible by both fragments.

If for some reason you can't use fragments ( although I strongly advise to do so ), then another solution may be to have some singleton object, where you store basket items. Note though, that usage of singleton objects is risky - for example, when you start updating data in singletons from different places, you may loose control on it at some point in time.

object TempBasketDataHolder {
    val basketItems: MutableList<Popular> = mutableListOf()
}

Then in your PopularDetailedActivity you can define methods to handle basket content:

fun clearBasket() {
        TempBasketDataHolder.basketItems.clear()
    }
    
    fun addBasketItem(item: Popular) {
        TempBasketDataHolder.basketItems.add(item)
    }

    fun removeBasketItem(item: Popular) {
        TempBasketDataHolder.basketItems.remove(item)
    }

In your MyCartActivity you can then access TempBasketDataHolder.basketItems correspondingly.