Empty View for Android's RecyclerView

readme.md

Empty View for Android's RecyclerView

Ejemplo de como implementar vista vacia en un RecyclerView usando Kotlin

BaseViewHolder.kt

import android.view.View
import androidx.recyclerview.widget.RecyclerView

abstract class BaseViewHolder<T>(itemView: View) : RecyclerView.ViewHolder(itemView) {
    abstract fun bind(item: T)
}

DeviceModel.kt

import java.util.*

data class DeviceModel(
    val status: Boolean,
    val name: String?,
    val macAddress: String,
    val detectDate: Date?,
    val uid: String = UUID.randomUUID().toString()
)

Fragment.kt

private lateinit var mAdapter: MyListAdapter
...
fun initRecyclerView() {
    mAdapter = MyListAdapter()
    mAdapter.emptyText = getString(R.string.allowed_devices_empty)
    list.adapter = mAdapter
}
...
fabAdd.setOnClickListener {
    val dataSet: MutableList<DeviceModel> = arrayListOf()
    dataSet.add(DeviceModel(true, "aaa22", "ff", null, "device1"))
    dataSet.add(DeviceModel(true, "bbb", "ff", null, "device2"))
    dataSet.add(DeviceModel(true, "ccc", "ff", null, "device3"))
    mAdapter.submitList(dataSet)
}

fabAdd.setOnLongClickListener {
    mAdapter.clearData()
    true
}

item_empty.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@android:id/text1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:gravity="center_horizontal"
        android:padding="8dp"
        android:paddingStart="?listPreferredItemPaddingStart"
        android:paddingEnd="?listPreferredItemPaddingEnd"
        android:text="@string/allowed_devices_empty"
        android:textAppearance="@style/TextAppearance.MaterialComponents.Caption"
        android:textColor="?android:textColorSecondary" />

</RelativeLayout>

MyDiffCallback.kt

class MyDiffCallback(
    private val oldItems: List<DeviceModel>,
    private val newItems: List<DeviceModel>
) : DiffUtil.Callback() {

    override fun getOldListSize(): Int = oldItems.size
    override fun getNewListSize(): Int = newItems.size

    override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean =
        oldItems[oldItemPosition].uid == newItems[newItemPosition].uid

    override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean =
        oldItems[oldItemPosition] == newItems[newItemPosition]

}

MyListAdapter.kt

import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.RecyclerView
import com.webserveis.mqtthomepresence.R
import com.webserveis.mqtthomepresence.commons.BaseViewHolder
import com.webserveis.mqtthomepresence.models.DeviceModel
class MyListAdapter : RecyclerView.Adapter<BaseViewHolder<*>>() {

    private var dataSet: MutableList<DeviceModel> = arrayListOf()
    var emptyText: String = "No data"

    companion object {
        private val TAG = MyListAdapter::class.java.simpleName
        private const val VIEW_TYPE_EMPTY = 0
        private const val VIEW_TYPE_ITEM = 1
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int) = when (viewType) {
        VIEW_TYPE_EMPTY -> EmptyViewHolder(
            LayoutInflater.from(parent.context)
                .inflate(R.layout.item_empty, parent, false)
        )
        VIEW_TYPE_ITEM -> MyViewHolder(
            LayoutInflater.from(parent.context)
                .inflate(R.layout.simple_list_item_2, parent, false)
        )
        else -> throw IllegalArgumentException("Invalid view type")
    }

    override fun onBindViewHolder(holder: BaseViewHolder<*>, position: Int) {
        if (position != RecyclerView.NO_POSITION) {
            when (holder) {
                is EmptyViewHolder -> holder.bind(emptyText)
                is MyViewHolder -> holder.bind(dataSet[position])
                else -> throw IllegalArgumentException("Invalid ViewHolder")
            }
        }
    }

    fun clearData() {
        val size: Int = dataSet.size
        dataSet.clear()
        notifyItemRangeRemoved(0, size)
    }

    fun submitList(newData: List<DeviceModel>) {

        val needNotifyDataChanged = dataSet.size == 0

        val diffResult = DiffUtil.calculateDiff(MyDiffCallback(dataSet, newData))
        diffResult.dispatchUpdatesTo(this)
        dataSet.clear()
        dataSet.addAll(newData)
        if (needNotifyDataChanged) notifyItemChanged(dataSet.size)
    }

    inner class MyViewHolder(itemView: View) : BaseViewHolder<DeviceModel>(itemView) {
        private val tvText1 = itemView.findViewById(android.R.id.text1) as TextView
        private val tvText2 = itemView.findViewById(android.R.id.text2) as TextView

        override fun bind(item: DeviceModel) {
            tvText1.text = item.name
            tvText2.text = item.macAddress
        }
    }

    inner class EmptyViewHolder(itemView: View) : BaseViewHolder<String>(itemView) {
        private val tvText1 = itemView.findViewById(android.R.id.text1) as TextView

        override fun bind(item: String) {
            tvText1.text = item
        }
    }

    override fun getItemViewType(position: Int): Int = if (dataSet.count() == 0) {
        VIEW_TYPE_EMPTY
    } else {
        VIEW_TYPE_ITEM
    }

    override fun getItemCount(): Int {
        return when (val count = dataSet.size) {
            0 -> 1
            else -> count
        }
    }

}

:)