Editor

CheeseAdapter.kt

/*
 * Copyright (C) 2017 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 paging.android.example.com.pagingsample

import android.arch.paging.PagedListAdapter
import android.support.v7.recyclerview.extensions.DiffCallback
import android.view.ViewGroup

/**
 * A simple PagedListAdapter that binds Cheese items into CardViews.
 * <p>
 * PagedListAdapter is a RecyclerView.Adapter base class which can present the content of PagedLists
 * in a RecyclerView. It requests new pages as the user scrolls, and handles new PagedLists by
 * computing list differences on a background thread, and dispatching minimal, efficient updates to
 * the RecyclerView to ensure minimal UI thread work.
 * <p>
 * If you want to use your own Adapter base class, try using a PagedListAdapterHelper inside your
 * adapter instead.
 *
 * @see android.arch.paging.PagedListAdapter
 * @see android.arch.paging.PagedListAdapterHelper
 */
class CheeseAdapter : PagedListAdapter<Cheese, CheeseViewHolder>(diffCallback) {
    override fun onBindViewHolder(holder: CheeseViewHolder, position: Int) {
        holder.bindTo(getItem(position))
    }

override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): CheeseViewHolder =
            CheeseViewHolder(parent)

companion object {
        /**
         * This diff callback informs the PagedListAdapter how to compute list differences when new
         * PagedLists arrive.
         * <p>
         * When you add a Cheese with the 'Add' button, the PagedListAdapter uses diffCallback to
         * detect there's only a single item difference from before, so it only needs to animate and
         * rebind a single view.
         *
         * @see android.support.v7.util.DiffUtil
         */
        private val diffCallback = object : DiffCallback<Cheese>() {
            override fun areItemsTheSame(oldItem: Cheese, newItem: Cheese): Boolean =
                    oldItem.id == newItem.id

/**
             * Note that in kotlin, == checking on data classes compares all contents, but in Java,
             * typically you'll implement Object#equals, and use it to compare object contents.
             */
            override fun areContentsTheSame(oldItem: Cheese, newItem: Cheese): Boolean =
                    oldItem == newItem
        }
    }
}