问Android Studio Kotlin: RecyclerView不能为空RuntimeException

EN

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.pos, PID: 6004
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.pos/com.example.pos.OrderActivity}: java.lang.IllegalStateException: orderRecyclerView must not be null
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.IllegalStateException: orderRecyclerView must not be null
        at com.example.pos.OrderActivity.onCreate(OrderActivity.kt:19)
        at android.app.Activity.performCreate(Activity.java:7009)
        at android.app.Activity.performCreate(Activity.java:7000)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

package com.example.pos

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.multiplerecyclerview.OrderAdapter
import kotlinx.android.synthetic.main.activity_order.*

class OrderActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)


        // Adapter class is initialized and list is passed in the param.
        val orderAdapter = OrderAdapter(this, getItemsList())

        //Set the LayoutManager that this RecyclerView will use.
        orderRecyclerView.layoutManager = LinearLayoutManager(this)

        //adapter instance is set to the recyclerview to inflate the items.
        orderRecyclerView.adapter = orderAdapter
    }

    private fun getItemsList(): ArrayList {
        val list = ArrayList()

        list.add(DataModel("Romana","1","12.50", "Pepperoni", "Aubergine", "Ex Mozz.", "Salami", OrderAdapter.TOPPINGS_4))
        list.add(DataModel("American","1","12.50", viewType = OrderAdapter.NO_TOPPING))

        return list
    }
}

package com.example.multiplerecyclerview

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.content.ContextCompat
import androidx.recyclerview.widget.RecyclerView
import com.example.pos.DataModel
import com.example.pos.R
import kotlinx.android.synthetic.main.food_item.view.*
import kotlinx.android.synthetic.main.food_item_4.view.*


class OrderAdapter(val context: Context, val items: ArrayList) :
    RecyclerView.Adapter() {

    companion object {
        const val NO_TOPPING = 1
        const val TOPPINGS_4 = 4
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): RecyclerView.ViewHolder {

        if(viewType == NO_TOPPING) {
            return ViewHolder(
                LayoutInflater.from(context).inflate(
                    R.layout.food_item,
                    parent,
                    false
                )
            )
        } else if (viewType == TOPPINGS_4) {
            return ViewHolder4(
                LayoutInflater.from(context).inflate(
                    R.layout.food_item_4,
                    parent,
                    false
                )
            )
        } else {
            return ViewHolder(
                LayoutInflater.from(context).inflate(
                    R.layout.food_item,
                    parent,
                    false
                )
            )
        }
    }

    override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
        val item = items.get(position)

        if(holder is ViewHolder) {

            holder.productQuantity.text = item.itemName
            holder.productName.text = item.itemName
            holder.productPrice.text = item.itemPrice

        } else if(holder is ViewHolder4) {

            holder.productQuantity4.text = item.itemName
            holder.productName4.text = item.itemName
            holder.productPrice4.text = item.itemPrice

            holder.topping1.text = item.topping1
            holder.topping2.text = item.topping2
            holder.topping3.text = item.topping3
            holder.topping4.text = item.topping4
        }

    }

    override fun getItemViewType(position: Int): Int {
        return items[position].viewType
    }

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

    class ViewHolder(view: View) : RecyclerView.ViewHolder(view) {
        val productQuantity = view.productQuantityView
        val productName = view.productNameView
        val productPrice = view.productPriceView
    }

    class ViewHolder4(view: View) : RecyclerView.ViewHolder(view) {
        val productQuantity4 = view.productQuantityView4
        val productName4 = view.productNameView4
        val productPrice4 = view.productPriceView4

        val topping1 = view.topping1View
        val topping2 = view.topping2View
        val topping3 = view.topping3View
        val topping4 = view.topping4View
    }
}

package com.example.pos

data class DataModel(val itemName: String, val itemQuantity: String, val itemPrice: String, val topping1: String? = null,  val topping2: String? = null,  val topping3: String? = null,  val topping4: String? = null, val viewType: Int)

food_item.xml



    

        

        

        

    



food_item4.xml