E/RecyclerView: No adapter attached; skipping layout(Kotlin) - android-studio

Question

I have a trouble with a error "E/RecyclerView: No adapter attached; skipping layout" for 2 days...
Please help me what causes this error...
I already checked that getItemCount function return 1 result(Because the ProductEntity database only have 1 data)
Thank you in advance!!
[ProductActivity.kt]
package com.example.trymakeapp
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.util.Log
import androidx.recyclerview.widget.LinearLayoutManager
import com.example.trymakeapp.databinding.ActivityProductBinding
import com.example.trymakeapp.databinding.ItemProductBinding
import com.example.trymakeapp.db.AppDatabase
import com.example.trymakeapp.db.ProductDao
import com.example.trymakeapp.db.ProductEntity
class ProductActivity : AppCompatActivity() {
private lateinit var binding: ActivityProductBinding
private lateinit var db: AppDatabase
private lateinit var productDao: ProductDao
private lateinit var productList : ArrayList<ProductEntity>
private lateinit var adapter : ProductRecyclerViewAdapter
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityProductBinding.inflate(layoutInflater)
setContentView(binding.root)
db = AppDatabase.getInstance(this)!!
productDao = db.getProductDao()
getAllProductList()
}
private fun getAllProductList() {
Thread {
productList = ArrayList(productDao.getAll())
setRecyclerView()
}.start()
println("#####")
}
private fun setRecyclerView() {
runOnUiThread {
adapter = ProductRecyclerViewAdapter(productList)
binding.recyclerView.adapter = adapter
binding.recyclerView.layoutManager = LinearLayoutManager(this#ProductActivity)
}
}
}
[ProductRecyclerViewAdapter.kt]
package com.example.trymakeapp
import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView
import com.example.trymakeapp.databinding.ItemProductBinding
import com.example.trymakeapp.db.ProductEntity
import java.util.ArrayList
class ProductRecyclerViewAdapter(private val productList : ArrayList<ProductEntity>)
: RecyclerView.Adapter<ProductRecyclerViewAdapter.MyViewHolder>() {
inner class MyViewHolder(binding: ItemProductBinding) :
RecyclerView.ViewHolder(binding.root) {
val product_idx = binding.productIdx
val product_name = binding.productName
val product_price = binding.productPrice
val product_img = binding.productImg
val root = binding.root
}
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
val binding : ItemProductBinding =
ItemProductBinding.inflate(LayoutInflater.from(parent.context),
parent, false)
return MyViewHolder(binding)
}
override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
val productData = productList[position]
holder.product_idx.text = productData.idx
holder.product_name.text = productData.name
holder.product_price.text = productData.price.toString()
}
override fun getItemCount(): Int {
return productList.size
}
}
[MainActivity.kt]
...
...
btn3.setOnClickListener {
val intent = Intent(this, ProductActivity::class.java)
startActivity(intent)
}

Answer 1

Try to move the initialization in the onCreate method:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityProductBinding.inflate(layoutInflater)
setContentView(binding.root)
db = AppDatabase.getInstance(this)!!
productDao = db.getProductDao()
binding.recyclerView.layoutManager = LinearLayoutManager(this)
adapter = ProductRecyclerViewAdapter(arrayListOf())
binding.recyclerView.adapter = adapter
getAllProductList()
}
And edit your setRecyclerView method like this (You can remove the adapter and productList global variables):
private fun setRecyclerView(productList: ArrayList<ProductEntity>) {
runOnUiThread {
binding.recyclerView.adapter = ProductRecyclerViewAdapter(productList)
}
}
EDIT
To handle the fact that data are not displayed. Try to use LiveData to observe its changes:
#Dao
interface ProductDao {
#Query("select * from ProductEntity")
fun getAll() : LiveData<List<ProductEntity>>
}
Then observe changes in the getAll method using observe:
private fun getAllProductList() {
productDao.getAll().observe(this) {
setRecyclerView(ArrayList(it))
}
}