im noob in kotlin... I have MainActivity and a list view inside.

When an item is clicked in list view, I want to update a textView inside MainActivity.

However because data should be passed from ListView to MainActivity, I did something weird.

MainActivity.kt

data class Country(val imgRes:Int, val name:String)

class MainActivity : AppCompatActivity() {
    private lateinit var binding : ActivityMainBinding
    private val data = arrayListOf<Country>()

    val imgRes = intArrayOf()

    val data1 = arrayOf()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)

        for(i in imgRes.indices) {
            val country = Country(imgRes[i], data1[i])
            data.add(country)
        }

        val adapter = RecyclerAdapter(data, object:RecyclerAdapter.OnItemClickListener {
            override fun onItemClick(v: View, pos: Int) {
                binding.textView.text = (v as TextView).text
            }
        })
        binding.recycler1.adapter = adapter
        binding.recycler1.layoutManager = StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL)
    }
}

ListView.kt

class RecyclerAdapter(private val dataSet:List<Country>, private val listener:OnItemClickListener) : RecyclerView.Adapter<RecyclerAdapter.ViewHolder>() {
    public interface OnItemClickListener {
        fun onItemClick(v:View, pos:Int)
    }

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

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

    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
        holder.bind(position)
    }

    inner class ViewHolder(val binding: RowBinding) : RecyclerView.ViewHolder(binding.root) {
        val rowImageView = binding.rowImageView
        val rowTextView = binding.rowTextView

        init {
            binding.root.setOnClickListener {
                listener.onItemClick(rowTextView, adapterPosition)
            }
        }

        fun bind(pos: Int) {
            with(binding) {
                rowImageView.setImageResource(dataSet[pos].imgRes)
                rowTextView.text = dataSet[pos].name
            }
        }
    }
}

I declared interface(OnItemClickListener) at ListView.kt and redefine it at MainActivity.kt. It works fine but is there any better way to do this?

CodePudding user response：

try this in your Adapter

var itemClickListener: ((position: Int, name: String) -> Unit)? = null

//bindviewholder

 itemClickListner.invoke(1,"anyvalue")

in activity

 adapter.itemClickListener = { 
            position, name ->
        Toast.makeText(requireContext(),"position is $position name is $name ",Toast.LENGTH_SHORT).show()
    }

CodePudding user response：

in adapter

private var mListener: OnItemClickListener,

 interface OnItemClickListener {
    fun onClick(position: Int, routerArray: ArrayList<Router>)
}


 binding.yourView.setOnClickListener {
            mListener.onClick(adapterPosition, routerArray)
        }

//in Activity

  override fun onClick(position: Int, yourArray: ArrayList<Model>) {
     binding.textView.text = yourArray[position].text
}