Type mismatch: inferred type is RecyclerAdapter but RecyclerView.Adapter<RecyclerView.ViewHolder&-CodePudding

I was learning about RecyclerViews and tried making one after watching this tutorial. Everything was going great until the very end when I got an error when connecting my adapter to my MainActivity.

The error I got in my MainActivity.kt was:

Type mismatch: inferred type is RecyclerAdapter but RecyclerView.Adapter<RecyclerView.ViewHolder>? was expected

Error is on line 22

This is my MainActivity.kt

package com.example.testing

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.recyclerview.widget.LinearLayoutManager
import androidx.recyclerview.widget.RecyclerView

class MainActivity : AppCompatActivity() {

    private var layoutManager: RecyclerView.LayoutManager? = null
    private var adapter: RecyclerView.Adapter<RecyclerView.ViewHolder>? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        val rvTest = findViewById<RecyclerView>(R.id.rvTest)

        layoutManager = LinearLayoutManager(this)
        rvTest.layoutManager = layoutManager

        adapter = RecyclerAdapter()
        rvTest.adapter = adapter
    }
}

And this is my RecyclerAdapter

package com.example.testing

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.ImageView
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView

class RecyclerAdapter: RecyclerView.Adapter<RecyclerAdapter.ViewHolder>() {

    private var Title = arrayOf("Cosmopolitan", "Vodka Sprite")
    private var Image = intArrayOf(R.drawable.ic_launcher_foreground, R.drawable.ic_launcher_background)

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

    override fun onBindViewHolder(holder: RecyclerAdapter.ViewHolder, position: Int) {
        holder.itemTitle.text = Title[position]
        holder.itemImage.setImageResource(Image[position])

    }

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

    inner class ViewHolder(itemView: View): RecyclerView.ViewHolder(itemView){
        var itemImage: ImageView
        var itemTitle: TextView

        init {
            itemImage = itemView.findViewById(R.id.imageView)
            itemTitle = itemView.findViewById(R.id.textView)
        }
    }

}

CodePudding user response：

In your MainActivity.kt

private var adapter: RecyclerView.Adapter<RecyclerView.ViewHolder>? = null

The datatype for adapter variable is wrong Change it to something like this

private var adapter: RecyclerAdapter? = null

Also instead of making it of type nullable, you can instead change to lateinit & make it non nullable type as it would be initialised inside onCreate

private lateinit var adapter: RecyclerAdapter

CodePudding user response：

change

 private var adapter: RecyclerView.Adapter<RecyclerView.ViewHolder>()

private var adapter: RecyclerView.Adapter<RecyclerAdapter.ViewHolder>

CodePudding user response：

You are extending the variable with the Extension RecyclerView.Adapter<RecyclerView.ViewHolder>() instead of the class RecyclerAdapter. Replace

private var adapter: RecyclerView.Adapter<RecyclerView.ViewHolder>? = null

with

private lateinit var adapter : RecyclerViewAdapter ?= null