Can i use ViewModelProvider and Observe in RecyclerView.Adapter?

Question

I user MVVM and RecyclerView in this app so the recycle view show the list perfectly but when i add the view model to adapter i get an error in the logcat

Your activity is not yet attached to the Application instance. You can't request ViewModel before onCreate call.

i am new in this MVVM and i know is this possible or is any other way to do this

this is my adapter class with the viewHolder

class KeefAdapter : RecyclerView.Adapter<KeefViewHolder>()

{ var dataOfAllKeef = listOf()

init {

    dataOfAllKeef = arrayListOf("Marijuwana" , "Bango" , "Weed" , "Hash")


}



override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): KeefViewHolder {

    lateinit var binding: KeefSingleItemBinding


    binding = DataBindingUtil.inflate(LayoutInflater.from(parent.context) , R.layout.keef_single_item , parent , false)


     val viewModel:OrderYourKeefViewModel = ViewModelProvider(OrderYourKeef()).get(OrderYourKeefViewModel::class.java)

    binding.orderViewModelWithSingle = viewModel


    viewModel.count.observe(OrderYourKeef(), Observer { newCountOfHash->

        binding.root.theCountOfHash.text = newCountOfHash.toString()
    })



    return KeefViewHolder(binding.root)
}



override fun getItemCount() = dataOfAllKeef.size




override fun onBindViewHolder(holder: KeefViewHolder, position: Int) {



    val item = dataOfAllKeef[position]

    holder.keefName.text = item





    if (item.equals("Marijuwana"))
    {
        holder.keefImage.setImageResource(R.mipmap.marijuana)

    }else if (item.equals("Bango"))
    {
        holder.keefImage.setImageResource(R.mipmap.bango)

    }else if (item.equals("Weed"))
    {
        holder.keefImage.setImageResource(R.mipmap.weed)

    }else if (item.equals("Hash"))
    {
        holder.keefImage.setImageResource(R.mipmap.hashesh)

    }

}

}

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

var keefName:TextView = itemView.keefName
var keefImage: ImageView = itemView.keefImage


var increase: Button = itemView.increaseTheCount
var decrease: Button = itemView.minusTheCount
var theCountOfKeef: TextView = itemView.theCountOfHash

}

Torben G Torben G · Accepted Answer · 2020-03-07T20:11:37

I think this is not the correct way to implement the mvvm pattern.

You have to call the viewModel = ViewModelProviders in your Activity. And after fetching the list items, pass it to your adapter and call the notifyDataSetChanged()

updateListItems(newListItems: List<YourItem>) {
 currentItems = newListItems
 notifyDataSetChanged()
}

Can i use ViewModelProvider and Observe in RecyclerView.Adapter?

1 Answers