sqlite - 如何在 AndroidStudio(Kotlin) 中连接数据库？

Question

package org.techtown.testrecyclerview.recommend

import android.content.Context
import android.content.Intent
import android.database.sqlite.SQLiteDatabase
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.Filterable
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import org.techtown.testrecyclerview.DBHelper
import org.techtown.testrecyclerview.R
import org.techtown.testrecyclerview.search.FoodData

class RecommendFoodAdapter (val context: Context, var foodList: ArrayList<FoodData>) :
    RecyclerView.Adapter<RecommendFoodAdapter.CustomViewHolder>() {
    lateinit var dbHelper : DBHelper
    lateinit var db : SQLiteDatabase

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

    override fun onBindViewHolder(holder: CustomViewHolder, position: Int) {
        //holder.bind(foodList[position], context)
        val item = foodList[position]

        holder.itemView.setOnClickListener {
            itemClickListner.onClick(it,position)
        }
        holder.apply {
            bind(item,context)
        }
    }

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

    interface OnItemClickListner {
        fun onClick(v:View, position: Int)
    }
    private lateinit var itemClickListner: OnItemClickListner

    fun setItemClickListner(itemClickListner: OnItemClickListner) {
        this.itemClickListner = itemClickListner
    }




    class CustomViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

        val foodTitle = itemView.findViewById<TextView>(R.id.titleTv)
        val kcalTv = itemView.findViewById<TextView>(R.id.kcalTv)
        val nutri1 = itemView.findViewById<TextView>(R.id.nutri1)
        val nutri2 = itemView.findViewById<TextView>(R.id.nutri2)
        val nutri3 = itemView.findViewById<TextView>(R.id.nutri3)

        val thumbUp = itemView.findViewById<ImageView>(R.id.thumbUpIv)
        val thumbDown = itemView.findViewById<ImageView>(R.id.thumbDownIv)
        var thumbCount = 0
        var thumbUpClicked : Boolean = false
        var thumbDownClicked : Boolean = false

        fun bind (foodData:FoodData, context: Context) {
            dbHelper = DBHelper(context, "food_nutri.db", null, 1)
            /* 나머지 TextView와 String 데이터를 연결한다. */
            foodTitle.text = foodData.foodName
            kcalTv.text = foodData.calorie.toString()+" | "+foodData.amount.toString()+"g 기준"
            nutri1.text = foodData.nutri1.toString()+"g"
            nutri2.text = foodData.nutri2.toString()+"g"
            nutri3.text = foodData.nutri3.toString()+"g"

            thumbUp.setOnClickListener {
                if (thumbUpClicked == true && thumbDownClicked == false) {
                    thumbCount--
                    thumbUpClicked = false
                    thumbUp.setImageResource(R.drawable.icons8_thumbs_up_24)
                    dbHelper.updatePriorityDown("해물찜&quot;)

                } else if (thumbUpClicked == false && thumbDownClicked == false) {
                    thumbCount++
                    thumbUpClicked = true
                    thumbUp.setImageResource(R.drawable.icons8_thumbs_up_filled_24)
                    dbHelper.updatePriorityUp("해물찜&quot;)
                }
            }
            thumbDown.setOnClickListener {
                if (thumbUpClicked == false && thumbDownClicked == true) {
                    thumbCount++
                    thumbDownClicked = false
                    thumbDown.setImageResource(R.drawable.icons8_thumbs_down_24)
                    dbHelper.updatePriorityUp(foodData.foodName)
                }
                else if (thumbUpClicked == false && thumbDownClicked == false) {
                    thumbCount--
                    thumbDownClicked = true
                    thumbDown.setImageResource(R.drawable.icons8_thumbs_down_filled_24)
                    dbHelper.updatePriorityDown(foodData.foodName)
                }
            }

        }

    }
}

嗨，我正在学习 Android Studio，我有一个问题。

在 CustomViewHolder 类中，我想连接 sqlite DB，但是“dbHelper = DBHelper(context, "food_nutri.db", null, 1)" 不起作用。在另一个 kotlin 类中，上面的 "dbHelper = DBHelper(context, "food_nutri.db", null, 1)" 效果很好，而在这个类中，它不起作用。我不知道为什么，请帮助我。

标签： sqliteandroid-studiokotlin