Animated Adapter for RecyclerView with model use-case

AnimatedAdapter.java

package com.judas.protos.recyclerview.adapters;

import android.support.v7.widget.RecyclerView;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;

public abstract class AnimatedAdapter<VH extends RecyclerView.ViewHolder, T> extends RecyclerView.Adapter<VH> {

    protected List<T> mOldItems;
    protected List<T> mNewItems;
    // Comparator for notifyItemChanged (return something other than 0 to update the item)
    protected Comparator<T> mUpdateComparator;

    public void notifyUpdate() {
        final List<T> tmpItems = new ArrayList<>(mOldItems);

        // 1 - Deleted items must be removed
        for (int i = mOldItems.size() - 1; i >= 0; i--) {
            if (!mNewItems.contains(mOldItems.get(i))) {
                notifyItemRemoved(i);
                tmpItems.remove(i);
            }
        }

        // 2 - Added items must be inserted
        for (int i = 0; i < mNewItems.size(); i++) {
            final T newItem = mNewItems.get(i);
            if (!mOldItems.contains(newItem)) {
                notifyItemInserted(i);
                tmpItems.add(i, newItem);
            }
        }

        // 3 - Items that switched place must be moved
        T misplacedItem = getMisplacedItem(tmpItems);
        while (misplacedItem != null) {
            final int oldPosition = tmpItems.indexOf(misplacedItem);
            final int newPosition = mNewItems.indexOf(misplacedItem);
            notifyItemMoved(oldPosition, newPosition);

            final T misplaced = tmpItems.remove(oldPosition);
            tmpItems.add(newPosition, misplaced);
            misplacedItem = getMisplacedItem(tmpItems);
        }

        // 4 - Items with new content must be updated
        if (mUpdateComparator != null) {
            for (int i = mNewItems.size() - 1; i >= 0; i--) {
                final T newItem = mNewItems.get(i);
                final T oldItem = tmpItems.get(i);
                if (mUpdateComparator.compare(oldItem, newItem) != 0) {
                    notifyItemChanged(i); // Item at i has changed
                }
            }
        }
    }

    private T getMisplacedItem(final List<T> tmpItems) {
        for (int i = 0; i < tmpItems.size(); i++) {
            final T oldItem = tmpItems.get(i);
            final int newPosition = mNewItems.indexOf(oldItem);

            if (i != newPosition)
                return oldItem;
        }
        return null;
    }
}

HomeActivity.java

package com.judas.protos.recyclerview.activities;

import android.graphics.Color;
import android.os.Bundle;
import android.os.Handler;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.SimpleItemAnimator;

import com.judas.protos.recyclerview.R;
import com.judas.protos.recyclerview.adapters.ItemAdapter;
import com.judas.protos.recyclerview.model.Item;

import java.util.ArrayList;
import java.util.List;

public class HomeActivity extends AppCompatActivity {

    private ItemAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.main);

        mAdapter = new ItemAdapter();

        final RecyclerView rv = (RecyclerView) findViewById(R.id.recycler);
        rv.setHasFixedSize(true);
        rv.setLayoutManager(new LinearLayoutManager(this, LinearLayoutManager.VERTICAL, false));
        rv.setAdapter(mAdapter);

        final SimpleItemAnimator animator = new DefaultItemAnimator();
        animator.setAddDuration(250);
        animator.setRemoveDuration(250);
        animator.setMoveDuration(500);
        animator.setChangeDuration(500);
        rv.setItemAnimator(animator);
    }

    private void reset() {
        final List<Item> items = new ArrayList<>();
        items.add(new Item("Item n°1", Color.RED, 1));
        items.add(new Item("Item n°2", Color.GREEN, 2));
        items.add(new Item("Item n°3", Color.BLUE, 3));
        items.add(new Item("Item n°4", Color.YELLOW, 4));
        items.add(new Item("Item n°5", Color.CYAN, 5));
        mAdapter.update(items, false);
    }

    private void shuffle() {
        final List<Item> items = new ArrayList<>();
        items.add(new Item("Item n°6", Color.MAGENTA, 6));
        items.add(new Item("Item n°2", Color.GREEN, 2));
        items.add(new Item("Item n°3", Color.BLUE, 3));
        items.add(new Item("Item n°1 UPDATED", Color.RED, 1));
        items.add(new Item("Item n°4", Color.YELLOW, 4));
        mAdapter.update(items, true);
    }

    @Override
    protected void onPostResume() {
        super.onPostResume();

        // Reset to original position
        reset();

        // Shuffle items after a delay
        new Handler().postDelayed(() -> shuffle(), 2000);
    }
}

Item.java

package com.judas.protos.recyclerview.model;

public class Item {
    private String mName;
    private int mColor;
    private int mId;

    public Item(final String name, final int color, final int id) {
        mName = name;
        mColor = color;
        mId = id;
    }

    public void setName(final String name) {
        mName = name;
    }

    public String getName() {
        return mName;
    }

    public int getColor() {
        return mColor;
    }

    @Override
    public boolean equals(final Object o) {
        if (o == null || !(o instanceof Item))
            return false;
        return mId == ((Item) o).mId;
    }
}

ItemAdapter.java

package com.judas.protos.recyclerview.adapters;

import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.judas.protos.recyclerview.R;
import com.judas.protos.recyclerview.model.Item;

import java.util.ArrayList;
import java.util.List;

public class ItemAdapter extends AnimatedAdapter<ItemViewHolder, Item> {

    public ItemAdapter() {
        // Set comparator for animation update (compare name fields)
        mUpdateComparator = (lhs, rhs) -> lhs.getName().compareTo(rhs.getName());
    }

    public ItemAdapter(final List<Item> items) {
        this();
        mNewItems = items;
    }

    @Override
    public ItemViewHolder onCreateViewHolder(final ViewGroup parent, final int viewType) {
        final View v = View.inflate(parent.getContext(), R.layout.item, null);
        final ItemViewHolder holder = new ItemViewHolder(v);
        v.setOnClickListener(v1 -> Toast.makeText(parent.getContext(), mNewItems.get(holder.getAdapterPosition()).getName(), Toast.LENGTH_SHORT).show());
        return holder;
    }

    @Override
    public void onBindViewHolder(final ItemViewHolder holder, final int position) {
        holder.bind(getItem(position));
    }

    @Override
    public int getItemCount() {
        return mNewItems == null ? 0 : mNewItems.size();
    }

    private Item getItem(final int position) {
        if (mNewItems == null || mNewItems.size() < position)
            return null;
        return mNewItems.get(position);
    }

    public void update(final List<Item> newItems, final boolean animated) {
        if (mNewItems == null || !animated) {
            mNewItems = newItems;
            notifyDataSetChanged();
        } else {
            mOldItems = new ArrayList<>(mNewItems);
            mNewItems = newItems;
            notifyUpdate();
        }
    }
}

ItemViewHolder.java

package com.judas.protos.recyclerview.adapters;

import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.TextView;

import com.judas.protos.recyclerview.R;
import com.judas.protos.recyclerview.model.Item;

public class ItemViewHolder extends RecyclerView.ViewHolder {

    private View mView;

    public ItemViewHolder(final View v) {
        super(v);
        mView = v;
    }

    public void bind(final Item item) {
        ((TextView) mView.findViewById(R.id.item_text)).setText(item.getName());
        mView.findViewById(R.id.item_avatar).setBackgroundColor(item.getColor());
    }
}