Empty state cursor recycler adapter

CursorAdapter.kt

package com.efectum.ui.base.adapter

import android.util.Log
import android.database.Cursor
import android.database.DataSetObserver
import androidx.recyclerview.widget.RecyclerView

abstract class CursorAdapter<VH : RecyclerView.ViewHolder>(cursor: Cursor?) : RecyclerView.Adapter<VH>() {

    var cursor: Cursor? = null
        private set

    protected var dataValid: Boolean = false

    private var rowIdColumn: Int = 0

    private val dataSetObserver: DataSetObserver?

    init {
        this.cursor = cursor
        dataValid = cursor != null
        rowIdColumn = if (dataValid) this.cursor!!.getColumnIndex("_id") else -1
        dataSetObserver = NotifyingDataSetObserver()
        if (this.cursor != null) {
            this.cursor!!.registerDataSetObserver(dataSetObserver)
        }
    }

    override fun getItemCount(): Int {
        if (dataValid) {
            return cursor?.count ?: 0
        }
        return 0
    }

    override fun getItemId(position: Int): Long {
        if (dataValid && cursor != null && cursor!!.moveToPosition(position)) {
            return cursor!!.getLong(rowIdColumn)
        }
        return 0
    }

    override fun setHasStableIds(hasStableIds: Boolean) {
        super.setHasStableIds(true)
    }

    abstract fun onBindViewHolder(viewHolder: VH, cursor: Cursor)

    override fun onBindViewHolder(viewHolder: VH, position: Int) {
        if (moveCursorToPosition(position)) {
            onBindViewHolder(viewHolder, cursor!!)
        }
    }

    protected fun moveCursorToPosition(position: Int): Boolean {
        if (!dataValid) {
            Log.e("Error", "this should only be called when the cursor is valid")
            return false
        }
        if (!cursor!!.moveToPosition(position)) {
            Log.e("Error", "couldn't move cursor to position $position")
            return false
        }
        return true
    }

    /**
     * Change the underlying cursor to a new cursor. If there is an existing cursor it will be
     * closed.
     */
    fun changeCursor(cursor: Cursor) {
        swapCursor(cursor)?.close()
    }

    /**
     * Swap in a new Cursor, returning the old Cursor.  Unlike
     * [.changeCursor], the returned old Cursor is *not*
     * closed.
     */
    private fun swapCursor(newCursor: Cursor): Cursor? {
        if (newCursor === cursor) {
            return null
        }
        val oldCursor = cursor
        if (dataSetObserver != null) {
            oldCursor?.unregisterDataSetObserver(dataSetObserver)
        }
        cursor = newCursor
        if (cursor != null) {
            if (dataSetObserver != null) {
                cursor!!.registerDataSetObserver(dataSetObserver)
            }
            rowIdColumn = newCursor.getColumnIndexOrThrow("_id")
            dataValid = true
            notifyDataSetChanged()
        } else {
            rowIdColumn = -1
            dataValid = false
            notifyDataSetChanged()
            //There is no notifyDataSetInvalidated() method in RecyclerView.Adapter
        }
        return oldCursor
    }

    private inner class NotifyingDataSetObserver : DataSetObserver() {
        override fun onChanged() {
            super.onChanged()
            dataValid = true
            notifyDataSetChanged()
        }

        override fun onInvalidated() {
            super.onInvalidated()
            dataValid = false
            notifyDataSetChanged()
            //There is no notifyDataSetInvalidated() method in RecyclerView.Adapter
        }
    }
}

EmptySearchCursorAdapter.kt

package com.efectum.ui.base.adapter

import android.database.Cursor
import android.view.View
import android.view.ViewGroup
import androidx.recyclerview.widget.RecyclerView

abstract class EmptySearchCursorAdapter<VH : RecyclerView.ViewHolder>(cursor: Cursor?) : CursorAdapter<RecyclerView.ViewHolder>(cursor) {

    override fun getItemViewType(position: Int) = if (super.getItemCount() == 0) {
        TYPE_EMPTY
    } else {
        TYPE_ITEM
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = when (viewType) {
        TYPE_ITEM -> {
            onCreateViewItemHolder(parent)
        }
        else -> {
            onCreateViewEmptyHolder(parent)
        }
    }

    override fun onBindViewHolder(viewHolder: RecyclerView.ViewHolder, position: Int) {
        when (getItemViewType(position)) {
            TYPE_ITEM -> {
                if (moveCursorToPosition(position)) {
                    @Suppress("UNCHECKED_CAST")
                    onBindViewItemHolder(viewHolder as VH, cursor!!)
                }
            }
        }
    }

    open fun onCreateViewEmptyHolder(parent: ViewGroup): RecyclerView.ViewHolder {
        return EmptyHolder(View(parent.context))
    }

    abstract fun onBindViewItemHolder(holder: VH, cursor: Cursor)

    abstract fun onCreateViewItemHolder(parent: ViewGroup): VH

    override fun getItemCount(): Int {
        val itemCount = super.getItemCount()
        if (itemCount == 0) {
            return 1
        }
        return itemCount
    }

    class EmptyHolder(itemView: View) : RecyclerView.ViewHolder(itemView)

    companion object {
        const val TYPE_EMPTY = 0
        const val TYPE_ITEM = 1
    }
}