Notify activity from adapter when item is deleted (emptyView)

November 03, 2018, at 03:20 AM

Let's define one variable in the begin, it will be more easier to read:
sqlite3 column KEY_TITLE = A

I have activity in conduction with cursor loader. When there are no rows in column A I want activity to display an emptyView. To do that, I created a method which checks all rows in column A if there is any data in it.

fun hideLayout(){
        val isEmpty = emptyViewObserver(applicationContext).isEmpty()
        if (isEmpty) {
            recyclerView.visibility = View.GONE
            emptyView.visibility = View.VISIBLE
        } else {
            recyclerView.visibility = View.VISIBLE
            emptyView.visibility = View.GONE

class emptyViewObserver with isEmpty method:

 class emptyViewObserver(val context: Context){
        fun isEmpty():Boolean{
            val db = WalletDbHelper(context).readableDatabase
            val projection = arrayOf(KEY_TITLE)
            val cursor = db.query(
            val names = mutableListOf<String>()
                while (moveToNext()){
                    val name = getString(cursor.getColumnIndexOrThrow(WalletEntry.KEY_TITLE))
            return names.isEmpty()

Whenever I perform any CRUD operation in MainActivity class I call hideLayout method to check out if emptyView should be shown or not. It works fine. But I'm facing problem after I perform delete operation from my adapter to call hideLayout() method. For obvious reasons it throws me error when calling it directly from adapter so I though about implementing interface and overriding this in MainActivity. I read some tutorials but I still didn't figure out how to implement this properly.

This is my delete method from adapter:

holder.delete.setOnClickListener { v ->
            val popup = PopupMenu(context, v)
            val inflater = popup.menuInflater
            popup.setOnMenuItemClickListener { v ->
              when(v.itemId) {
         -> {
                      delete(uri, walletName)
                  else -> {

and delete():

fun delete(uri: String, walletName: String){
        val newUri: Uri = Uri.parse(uri)
        context.contentResolver.delete(newUri, WalletEntry.KEY_TITLE, arrayOf(walletName))

Do you have any ideas how can I write this code?

Answer 1

You need a callback, When you delete some item, check if is the last one and if it is true call that.

Add this interface on your adapter:

interface OnListIsEmpty{
    fun onListIsEmpty()

And create a object of this like global variable in your adapter too:

private var mOnListIsEmpty: OnListIsEmpty? = null

Add a setter method:

fun setOnListIsEmpty(onListIsEmpty: OnListIsEmpty){
    this.mOnListIsEmpty = onListIsEmpty

And in your delete method do the validation if is empty if it is true then:


And not forget set the callback when you initilize the adapter with:

adapter.setOnListIsEmpty(object : OnListIsEmpty{
        override fun onListIsEmpty() {
            //your action
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