How can I access a variable located in an adapter class from main activity

Question

I want to access a variable in an adapter class called item so that I could use it in my main activity. So far I've tried adding open before the adapter class and using object and companion object. How can I fix this problem?

class GrammarAdapter(private val context: Context, private val items: ArrayList<String>) :
    RecyclerView.Adapter<GrammarAdapter.ViewHolder>() {

    class ViewHolder(binding: GrammarItemRowBinding) : RecyclerView.ViewHolder(binding.root) {
        val tvItem = binding.tvItemName
    }


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
        return ViewHolder(
            GrammarItemRowBinding.inflate(LayoutInflater.from(context), parent, false)
        )
    }

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        val item = items[position]
        holder.tvItem.text = item



        holder.itemView.setOnClickListener {
            when (item) {
                "Countable and uncountable nouns" -> {
                    val intent = Intent(holder.itemView.context, CountableUncountable::class.java)
                    intent.putExtra("clickedGrammarTopic", item)
                    holder.itemView.context.startActivity(intent)
                }
                "Singular and plural nouns" -> {
                    val intent = Intent(holder.itemView.context, Singular and plural nouns::class.java)
                    intent.putExtra("clickedGrammarTopic", item)
                    holder.itemView.context.startActivity(intent)
                }
...

I've checked that one before asking the question but it was all in Java and for a beginner like me it is impossible to make the connection with Kotlin. — Aschente, May 18 '21 at 19:21

score 1 · Answer 1 · answered May 18 '21 at 18:54

1

As long as items is not private you can do something like:

val item = (myRecycler.adapter as MyAdapterClass).items[position]

However thats not really the best practice and you may want to rethink how your managing your apps data perhaps you should look into ViewModels

answered May 18 '21 at 18:54

Quinn

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Sorry, I guess I used my .adapter as a view binder. Can I bother you to have a look at a couple more lines? I just edited the question. This is my first time coding with kotlin so I hope I didn't make your eyes bleed. – Aschente May 18 '21 at 19:06

score 0 · Answer 2 · answered May 18 '21 at 19:35

You have to use the callback pattern via an interface

interface Callback {
    fun onClickedRow(item: String)
}

In the adapter constructor

class GrammarAdapter(... , private val callback: Callback) : ...

And modify the interaction

holder.itemView.setOnClickListener {
    callback.onClickedRow(item)
}

You have to implement the interface in the activity or fragment

clas MyFragment : Callback {

    override fun onClickedRow(item: String) {
         //do something here with your item
    }
}

And instantiate your adapter with the callback as an argument

val adapter = GrammarAdapter(..., this@MyFragment) //depending on your scope it can be simple this

Now when the user clicks the method override fun onClickedRow(... is going to be triggered on the activity or fragment

How can I access a variable located in an adapter class from main activity

2 Answers2