Fill a ViewGroup with items using a given layout. Easy to replace, reuses child views if possible.

ViewGroupExt.kt

/**
  Copyright 2019 Joshua Kovach

  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.
*/

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.annotation.LayoutRes
import androidx.core.view.get

/**
 * A simple adapter implementation for [ViewGroup] to update items within a specific range of the
 * child views. When called, the view will insert or remove children after [startIndex] and before
 * [endOffset] using the provided layout until the number of children within that range equals the
 * number of [items], and will then call [onBind] for each of the child items in that range.
 *
 * @param [layoutId] a layout resource id
 * @param [items] a list of type [T] to be used when updating and binding the views
 * @param [startIndex] index at which to begin inserting or updating child views
 * @param [endOffset] number of views at the end of the LinearLayout to preserve when updating
 * @param [onBind] a callback to update the view using the item at the provided index from [items]
 */
inline fun <reified T> ViewGroup.setItems(
    @LayoutRes layoutId: Int,
    items: List<T>,
    startIndex: Int = 0,
    endOffset: Int = 0,
    onBind: (View, T, Int) -> Unit
) {
    while (childCount < items.count() + startIndex + endOffset) {
        inflate(layoutId, childCount - endOffset)
    }

    while (childCount > items.count() + startIndex + endOffset) {
        removeViewAt(childCount - 1 - endOffset)
    }

    items.forEachIndexed { index, item ->
        val view = get(index + startIndex)
        onBind(view, item, index)
    }
}

val Context.layoutInflater: LayoutInflater get() = LayoutInflater.from(this)

val View.layoutInflater: LayoutInflater get() = context.layoutInflater

fun ViewGroup.inflate(@LayoutRes layoutId: Int, attachToRoot: Boolean = false): View =
    layoutInflater.inflate(layoutId, this, attachToRoot)

fun ViewGroup.inflate(@LayoutRes layoutId: Int, index: Int): View =
    inflate(layoutId, false).also { addView(it, index) }