Selection Recyclerview List using live data, viewmodel and list adapter

fragment_selection_list.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.coordinatorlayout.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.google.android.material.appbar.AppBarLayout
        android:id="@+id/app_bar_layout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#FFFFFF"
        app:liftOnScroll="true">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:id="@+id/cl_toolbar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:background="@color/cardForeground"
            android:gravity="center_vertical"
            android:orientation="horizontal">

            <ImageView
                android:id="@+id/image_back"
                style="@style/ToolbarIcon"
                android:layout_marginTop="8dp"
                android:layout_marginStart="8dp"
                android:src="@drawable/ic_left_arrow"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

            <TextView
                style="@style/ToolbarTitle"
                android:layout_width="0dp"
                android:layout_height="0dp"
                android:layout_marginStart="8dp"
                android:layout_marginEnd="8dp"
                android:gravity="center_vertical"
                android:text="Mileage"
                app:layout_constraintBottom_toBottomOf="@id/image_back"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintStart_toEndOf="@id/image_back"
                app:layout_constraintTop_toTopOf="@id/image_back" />

            <ImageView
                android:id="@+id/image_delete"
                style="@style/ToolbarIcon"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:layout_marginTop="8dp"
                android:layout_marginBottom="8dp"
                android:src="@drawable/ic_delete"
                android:layout_marginEnd="8dp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent" />

            <com.google.android.material.button.MaterialButton
                android:id="@+id/text_select"
                style="@style/FlatButton"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="8dp"
                android:layout_marginBottom="8dp"
                android:layout_marginTop="8dp"
                android:text="Select"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/image_back" />

            <com.google.android.material.button.MaterialButton
                android:id="@+id/text_select_all"
                style="@style/FlatButton"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="8dp"
                android:layout_marginBottom="8dp"
                android:layout_marginTop="8dp"
                android:text="Select All"
                android:visibility="invisible"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toBottomOf="@+id/image_back" />

            <View
                android:id="@+id/divider"
                android:layout_width="1dp"
                android:layout_height="0dp"
                android:layout_marginTop="4dp"
                android:layout_marginBottom="4dp"
                android:layout_marginStart="8dp"
                android:background="@color/colorPrimary"
                app:layout_constraintBottom_toBottomOf="@id/text_create_list"
                app:layout_constraintStart_toEndOf="@id/text_select_all"
                app:layout_constraintTop_toTopOf="@id/text_create_list" />

            <com.google.android.material.button.MaterialButton
                android:id="@+id/text_create_list"
                style="@style/FlatButton.Icon"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginStart="8dp"
                android:layout_marginBottom="8dp"
                android:layout_marginTop="8dp"
                android:text="Create New List"
                app:icon="@drawable/ic_plus_circle"
                android:background="?attr/selectableItemBackground"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintStart_toEndOf="@id/divider" />

        </androidx.constraintlayout.widget.ConstraintLayout>

    </com.google.android.material.appbar.AppBarLayout>

    <androidx.core.widget.NestedScrollView
        android:id="@+id/nested_scrollview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior" >

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/rv_list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical" />

    </androidx.core.widget.NestedScrollView>

</androidx.coordinatorlayout.widget.CoordinatorLayout>

item_selection.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <View
        android:layout_width="0dp"
        android:layout_height="0dp"
        android:elevation="10dp"
        android:background="?attr/selectableItemBackground"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/image_selector"
        android:layout_width="24dp"
        android:layout_height="24dp"
        android:layout_marginStart="8dp"
        android:src="@drawable/ic_circle_empty"
        android:visibility="gone"
        app:layout_constraintBottom_toBottomOf="@id/card_item"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@id/card_item" />

    <com.google.android.material.card.MaterialCardView
        android:id="@+id/card_item"
        style="@style/itemCard"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginTop="16dp"
        android:layout_marginEnd="8dp"
        android:layout_marginBottom="16dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@id/image_selector"
        app:layout_constraintTop_toTopOf="parent">

        <androidx.constraintlayout.widget.ConstraintLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content">

            <TextView
                android:id="@+id/text_date"
                style="@style/accentText"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginStart="16dp"
                android:padding="0dp"
                android:text="02-01-2019"
                android:singleLine="true"
                android:ellipsize="end"
                android:textStyle="bold"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@+id/text_mile_number"
                app:layout_constraintStart_toStartOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

            <TextView
                android:id="@+id/text_mile_number"
                style="@style/primaryText.Medium"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:padding="0dp"
                android:text="45.2"
                android:textAlignment="center"
                android:textStyle="bold"
                android:layout_marginTop="16dp"
                app:layout_constraintTop_toTopOf="parent"
                app:layout_constraintBottom_toTopOf="@+id/text_mile"
                app:layout_constraintEnd_toEndOf="@+id/text_mile"
                app:layout_constraintStart_toStartOf="@+id/text_mile" />

            <TextView
                android:id="@+id/text_mile"
                style="@style/primaryText"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:text="MILES"
                android:singleLine="true"
                android:ellipsize="end"
                android:textAllCaps="true"
                android:layout_marginBottom="16dp"
                android:layout_marginEnd="16dp"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintTop_toBottomOf="@id/text_mile_number"
                app:layout_constraintEnd_toStartOf="@id/divider" />

            <ImageView
                android:id="@+id/image_arrow"
                style="@style/imageIcon"
                android:layout_width="40dp"
                android:layout_height="40dp"
                android:background="#fff"
                android:padding="8dp"
                android:src="@drawable/ic_right_arrow"
                android:tint="@color/iconSecondary"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toEndOf="parent"
                app:layout_constraintTop_toTopOf="parent" />

            <TextView
                android:id="@+id/text_property_number"
                style="@style/primaryText.Medium"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:padding="0dp"
                android:text="56"
                android:textAlignment="center"
                android:textStyle="bold"
                android:singleLine="true"
                android:ellipsize="end"
                android:layout_marginTop="16dp"
                app:layout_constraintBottom_toTopOf="@+id/text_property"
                app:layout_constraintEnd_toEndOf="@+id/text_property"
                app:layout_constraintStart_toStartOf="@+id/text_property"
                app:layout_constraintTop_toTopOf="parent" />

            <TextView
                android:id="@+id/text_property"
                style="@style/primaryText"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:text="Properties"
                android:textAllCaps="true"
                android:singleLine="true"
                android:ellipsize="end"
                android:layout_marginBottom="16dp"
                app:layout_constraintTop_toBottomOf="@id/text_property_number"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@id/image_arrow" />

            <View
                android:id="@+id/divider"
                android:layout_width="1dp"
                android:layout_height="0dp"
                android:layout_marginTop="16dp"
                android:layout_marginEnd="16dp"
                android:layout_marginBottom="16dp"
                android:background="@color/iconSecondary"
                app:layout_constraintBottom_toBottomOf="parent"
                app:layout_constraintEnd_toStartOf="@id/text_property"
                app:layout_constraintTop_toTopOf="parent" />

        </androidx.constraintlayout.widget.ConstraintLayout>

    </com.google.android.material.card.MaterialCardView>
</androidx.constraintlayout.widget.ConstraintLayout>

ListState.kt

enum class ListState(val state: Int) {
    OPEN_SELECTION(0),
    CLOSED_SELECTION(0),
    SELECT_ALL(0)
}

SelectionListAdapter.kt

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

class SelectionListAdapter(private val onItemClickListener: () -> Unit) :
    ListAdapter<String, SelectionListAdapter.SelectionViewHolder>(
        SelectionDiffUtil()
    ) {

    private var listState: ListState = ListState.CLOSED_SELECTION

    override fun onCreateViewHolder(
        parent: ViewGroup,
        viewType: Int
    ): SelectionViewHolder {
        val view = LayoutInflater.from(parent.context).inflate(viewType, parent, false)
        return SelectionViewHolder(view, onItemClickListener)
    }

    override fun getItemViewType(position: Int): Int {
        return R.layout.item_selection
    }

    fun setListState(state: ListState) {
        listState = state
        this.notifyDataSetChanged()
    }

    override fun onBindViewHolder(
        holder: SelectionViewHolder,
        position: Int
    ) {
        holder.bind(getItem(position), listState)
    }

    class SelectionViewHolder(val view: View, private val onItemClickListener: () -> Unit) :
        RecyclerView.ViewHolder(view) {

        // TODO: This is for test purpose Remove isSelected from here when we apply databinding
        var isSelected = false

        fun bind(item: String, listState: ListState) {
            view.setOnClickListener {
                if (listState == ListState.OPEN_SELECTION || listState == ListState.SELECT_ALL) {
                    isSelected = !isSelected
                    isSelectedItem(isSelected)
                } else {
                    onItemClickListener.invoke()
                }
            }

            when (listState) {
                ListState.OPEN_SELECTION -> {
                    enableSelection(enable = true)
                }
                ListState.SELECT_ALL -> {
                    isSelected = true
                    isSelectedItem(isSelected)
                    enableSelection(enable = true)
                }
                ListState.CLOSED_SELECTION -> {
                    isSelected = false
                    isSelectedItem(isSelected)
                    enableSelection(enable = false)
                }
            }
        }

        private fun isSelectedItem(selected: Boolean) {
            val imageViewItemSelector = view.findViewById<ImageView>(R.id.image_selector)
            if (selected) {
                imageViewItemSelector.setImageResource(R.drawable.ic_circle_tick)
            } else {
                imageViewItemSelector.setImageResource(R.drawable.ic_circle_empty)
            }
        }

        private fun enableSelection(enable: Boolean) {
            val imageViewItemSelector = view.findViewById<ImageView>(R.id.image_selector)
            if (enable) {
                imageViewItemSelector.visibility = View.VISIBLE
            } else {
                imageViewItemSelector.visibility = View.GONE
            }
        }
    }

    class SelectionDiffUtil : DiffUtil.ItemCallback<String>() {
        override fun areItemsTheSame(oldItem: String, newItem: String): Boolean {
            return oldItem == newItem
        }

        override fun areContentsTheSame(oldItem: String, newItem: String): Boolean {
            return oldItem == newItem
        }
    }
}

SelectionListFragment.kt

import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.core.widget.NestedScrollView
import androidx.fragment.app.Fragment
import androidx.lifecycle.Observer
import androidx.lifecycle.ViewModelProviders
import androidx.recyclerview.widget.LinearLayoutManager

class MileageFragment : Fragment() {

    private lateinit var listAdapter: SelectionListAdapter
    private lateinit var viewModel: SelectionListViewModel

    override fun onCreateView(
        inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        return inflater.inflate(R.layout.fragment_selection_list, container, false)
    }

    override fun onActivityCreated(savedInstanceState: Bundle?) {
        super.onActivityCreated(savedInstanceState)
        viewModel = ViewModelProviders.of(this).get(SelectionListViewModel::class.java)
        setupAdapter()

        viewModel.listState.observe(this, Observer {
            listAdapter.setListState(it)
        })

        nested_scrollview.setOnScrollChangeListener { v: NestedScrollView?,
                                                      scrollX: Int,
                                                      scrollY: Int,
                                                      oldScrollX: Int,
                                                      oldScrollY: Int ->
            if (scrollY <= 0) {
                app_bar_layout.setLifted(false)
            }
        }

        image_back.setOnClickListener {
            if (viewModel.listState.value == ListState.OPEN_SELECTION ||
                viewModel.listState.value == ListState.SELECT_ALL
            ) {
                text_select.visibility = View.VISIBLE
                text_select_all.visibility = View.INVISIBLE
                viewModel.setListState(ListState.CLOSED_SELECTION)
            }
        }

        text_select_all.setOnClickListener {
            viewModel.setListState(ListState.SELECT_ALL)
        }

        text_select.setOnClickListener {
            text_select.visibility = View.INVISIBLE
            text_select_all.visibility = View.VISIBLE
            viewModel.setListState(ListState.OPEN_SELECTION)
        }
    }

    private fun setupAdapter() {
        listAdapter = SelectionListAdapter {
            //Navigation
        }
        rv_list.apply {
            adapter = listAdapter
            layoutManager = LinearLayoutManager(requireContext())
        }

        listAdapter.submitList(listOf("", "", "", "", "", "", "", ""))
    }

    companion object {
        fun newInstance() = MileageFragment()
    }
}

SelectionListViewModel.kt

import android.app.Application
import androidx.lifecycle.AndroidViewModel
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData

class SelectionListViewModel(app: Application) : AndroidViewModel(app) {

    private val _listState: MutableLiveData<ListState> = MutableLiveData(ListState.CLOSED_SELECTION)
    val listState: LiveData<ListState> = _listState

    fun setListState(state: ListState) {
        _listState.value = state
    }
}