I am making recyclerview in kotlin in android studio. I'm trying to set up an event listener that puts a button in the recyclerview and outputs a toast message. Even if this@[activity name] is entered instead of this in context, a toast message is not displayed. What went wrong?

The error code is as follows.

Unresolved reference: @UpdateActivity

class UpdateActivity : AppCompatActivity() {

    private val vBinding by lazy {ActivityUpdateBinding.inflate(layoutInflater)}

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(vBinding.root)
        var recyclerViewAdapter = CustomAdapter()
        recyclerViewAdapter.listData = arrayListOf<String>("a", "b", "c")
        vBinding.uploadedRecyclerView.adapter = recyclerViewAdapter
        vBinding.uploadedRecyclerView.layoutManager = LinearLayoutManager(this)
    } // onCreate End


    class CustomAdapter:RecyclerView.Adapter<CustomAdapter.Holder>(){
        var listData = arrayListOf<String>()
        class Holder(val vBinding:UploadedRecyclerBinding):RecyclerView.ViewHolder(vBinding.root){
            fun setData(name:String){
                vBinding.name.text = name
                vBinding.getBtn.setOnClickListener {
                    **Toast.makeText(this@UpdateActivity, "test", Toast.LENGTH_SHORT).show()**
                                       // ↑A compilation error occurs here.**
                }
            }
        } // Holder end
        override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): Holder {
            val vBinding = UploadedRecyclerBinding.inflate(LayoutInflater.from(parent.context), parent, false)
            return Holder(vBinding)
        }
        override fun onBindViewHolder(holder: Holder, position: Int) {
            val name = listData[position]
            holder.setData(name)
        }
        override fun getItemCount(): Int {
            return listData.size
        }
    } // CustomAdapter end

} // UpdateActivity end

CodePudding user response：

you could try put context into constructor of adapter when you create it, and use this context to show a toast. something like this:

class CustomAdapter(
    private val mContext: Context
):RecyclerView.Adapter<CustomAdapter.Holder>(){

and in holder class:

Toast.makeText(mContext, "test", Toast.LENGTH_SHORT).show()

finally, when you create adapter in activity:

var recyclerViewAdapter = CustomAdapter(this)

Normally, we'll create adapter class in another file, so use this@UpdateActivity in adapter is bad idea

CodePudding user response：

Instead of using the local context in Toast, always use applicationContext when showing it. So, you should replace that creation of Toast message as,

Toast.makeText(applicationContext, "test", Toast.LENGTH_SHORT).show()