DiffCallback.java

package com.mikepenz.fastadapter.commons.utils;

import android.support.annotation.Nullable;
import android.support.v7.widget.RecyclerView;

/**
 * DiffCallback used to efficiently update the items inside the list with the new DiffUtils
 */
public interface DiffCallback<Item> {
    /**
     * Called by the DiffUtil to decide whether two object represent the same Item.
     * For example, if your items have unique ids, this method should check their id equality.
     *
     * @param oldItem the item in the old list
     * @param newItem the item in the new list
     * @return True if the two items represent the same object or false if they are different.
     */
    boolean areItemsTheSame(Item oldItem, Item newItem);

    /**
     * Called by the DiffUtil when it wants to check whether two items have the same data.
     * DiffUtil uses this information to detect if the contents of an item has changed.
     * DiffUtil uses this method to check equality instead of {@link Object#equals(Object)}
     * so that you can change its behavior depending on your UI.
     * For example, if you are using DiffUtil with a
     * {@link android.support.v7.widget.RecyclerView.Adapter RecyclerView.Adapter}, you should
     * return whether the items' visual representations are the same.
     * This method is called only if #areItemsTheSame(Item, Item) returns
     * {@code true} for these items.
     *
     * @param oldItem the item in the old list
     * @param newItem the item in the new list
     * @return True if the contents of the items are the same or false if they are different.
     */
    boolean areContentsTheSame(Item oldItem, Item newItem);

    /**
     * When {#areItemsTheSame(Item, Item)} returns {@code true} for two items and
     * {#areContentsTheSame(Item, Item)} returns false for them, DiffUtil
     * calls this method to get a payload about the change.
     * For example, if you are using DiffUtil with {@link RecyclerView}, you can return the
     * particular field that changed in the item and your
     * {@link android.support.v7.widget.RecyclerView.ItemAnimator ItemAnimator} can use that
     * information to run the correct animation.
     * Default implementation returns {@code null}.
     *
     * @param oldItemPosition The position of the item in the old list
     * @param newItemPosition The position of the item in the new list
     * @return A payload object that represents the change between the two items.
     */
    @Nullable
    Object getChangePayload(Item oldItem, int oldItemPosition, Item newItem, int newItemPosition);
}