Customising the DividerItemDecoration class so we can remove divider / decorator after the last item [Kotlin]

DividerItemDecoration.kt

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.v7.widget;

import android.annotation.SuppressLint
import android.content.Context
import android.graphics.Canvas
import android.graphics.Rect
import android.graphics.drawable.Drawable
import android.util.Log
import android.view.View
import android.widget.LinearLayout
import androidx.annotation.NonNull
import androidx.recyclerview.widget.RecyclerView
import androidx.recyclerview.widget.RecyclerView.ItemDecoration
import kotlin.math.roundToInt

/**
 * DividerItemDecoration is a {@link RecyclerView.ItemDecoration} that can be used as a divider
 * between items of a {@link LinearLayoutManager}. It supports both {@link #HORIZONTAL} and
 * {@link #VERTICAL} orientations.
 *
 * <pre>
 *     mDividerItemDecoration = new DividerItemDecoration(recyclerView.getContext(),
 *             mLayoutManager.getOrientation());
 *     recyclerView.addItemDecoration(mDividerItemDecoration);
 * </pre>
 */

//Find out original java version: https://gist.github.com/johnwatsondev/720730cf6b8c59fa6abe4f31dbaf59d7

@SuppressLint("LogNotTimber")
class DividerItemDecoration(context: Context, orientation: Int, isShowInLastItem: Boolean) :
    ItemDecoration() {
    private var mDivider: Drawable?

    /**
     * Current orientation. Either [.HORIZONTAL] or [.VERTICAL].
     */
    private var mOrientation = 0

    //    private final Rect mBounds = new Rect();
    private val mIsShowInLastItem: Boolean

    /**
     * Sets the orientation for this divider. This should be called if
     * [RecyclerView.LayoutManager] changes orientation.
     *
     * @param orientation [.HORIZONTAL] or [.VERTICAL]
     */
    fun setOrientation(orientation: Int) {
        require(!(orientation != HORIZONTAL && orientation != VERTICAL)) { "Invalid orientation. It should be either HORIZONTAL or VERTICAL" }
        mOrientation = orientation
    }

    /**
     * Sets the [Drawable] for this divider.
     *
     * @param drawable Drawable that should be used as a divider.
     */
    fun setDrawable(@NonNull drawable: Drawable?) {
        requireNotNull(drawable) { "Drawable cannot be null." }
        mDivider = drawable
    }

    override fun onDraw(c: Canvas, parent: RecyclerView, state: RecyclerView.State) {
        if (parent.layoutManager == null || mDivider == null) {
            return
        }
        if (mOrientation == VERTICAL) {
            drawVertical(c, parent)
        } else {
            drawHorizontal(c, parent)
        }
    }

    private fun drawVertical(canvas: Canvas, parent: RecyclerView) {
        canvas.save()
        val left: Int = parent.paddingLeft
        val right: Int = parent.width - parent.paddingRight
        canvas.clipRect(
            left, parent.paddingTop, right,
            parent.height - parent.paddingBottom
        )
        val childCount: Int = if (mIsShowInLastItem) {
            parent.childCount
        } else {
            parent.childCount - 1
        }
        for (i in 0 until childCount) {
            val child = parent.getChildAt(i)
            val decoratedBottom = parent.layoutManager!!.getDecoratedBottom(child)
            val bottom = decoratedBottom + Math.round(child.translationY)
            val top = bottom - mDivider!!.intrinsicHeight
            mDivider!!.setBounds(left, top, right, bottom)
            mDivider!!.draw(canvas)
        }
        canvas.restore()
    }

    private fun drawHorizontal(canvas: Canvas, parent: RecyclerView) {
        canvas.save()
        val top: Int = parent.paddingTop
        val bottom: Int = parent.height - parent.paddingBottom
        canvas.clipRect(
            parent.paddingLeft, top,
            parent.width - parent.paddingRight, bottom
        )
        val childCount: Int = if (mIsShowInLastItem) {
            parent.childCount
        } else {
            parent.childCount - 1
        }
        for (i in 0 until childCount) {
            val child = parent.getChildAt(i)
            val decoratedRight = parent.layoutManager!!.getDecoratedRight(child)
            val right = decoratedRight + child.translationX.roundToInt()
            val left = right - mDivider!!.intrinsicWidth
            mDivider!!.setBounds(left, top, right, bottom)
            mDivider!!.draw(canvas)
        }
        canvas.restore()
    }

    override fun getItemOffsets(
        outRect: Rect,
        view: View,
        parent: RecyclerView,
        state: RecyclerView.State
    ) {
        if (mDivider == null) {
            outRect.setEmpty()
            return
        }
        val itemPosition = (view.layoutParams as RecyclerView.LayoutParams).viewLayoutPosition
        val itemCount = state.itemCount
        if (mIsShowInLastItem) {
            if (mOrientation == VERTICAL) {
                outRect[0, 0, 0] = mDivider!!.intrinsicHeight
            } else {
                outRect[0, 0, mDivider!!.intrinsicWidth] = 0
            }
        } else if (itemPosition == itemCount - 1) {
            // We didn't set the last item when mIsShowInLastItem's value is false.
            outRect.setEmpty()
        } else {
            if (mOrientation == VERTICAL) {
                outRect[0, 0, 0] = mDivider!!.intrinsicHeight
            } else {
                outRect[0, 0, mDivider!!.intrinsicWidth] = 0
            }
        }
    }

    companion object {
        const val HORIZONTAL = LinearLayout.HORIZONTAL
        const val VERTICAL = LinearLayout.VERTICAL
        private const val TAG = "DividerItem"
        private val ATTRS = intArrayOf(android.R.attr.listDivider)
    }

    /**
     * Creates a divider [RecyclerView.ItemDecoration] that can be used with a
     * [LinearLayoutManager].
     *
     * @param context          Current context, it will be used to access resources.
     * @param orientation      Divider orientation. Should be [.HORIZONTAL] or [.VERTICAL].
     * @param isShowInLastItem Whether show the divider in last item.
     */
    init {
        val a = context.obtainStyledAttributes(ATTRS)
        mDivider = a.getDrawable(0)
        if (mDivider == null) {
            Log.w(
                TAG,
                "@android:attr/listDivider was not set in the theme used for this "
                        + "DividerItemDecoration. Please set that attribute all call setDrawable()"
            )
        }
        a.recycle()
        setOrientation(orientation)
        mIsShowInLastItem = isShowInLastItem
    }
}