diffutil-sample's Introduction

DiffUtil Android Sample - Kotlin

Example of usage DiffUtil utility class added originally in Support Library 24.2.0.

Demo

Implementation

calculateDiff method from DiffUtill class requires DiffUtil.Callback object as parameter.

DiffUtil callback - ActorDiffCallback.kt

Implements 4 methods:

getOldListSize - returns size of the old list
getNewListSize - returns size of the new list
areItemsTheSame - returns true if two items are the same, e.g. have the same ids
areContentsTheSame - returns true if displayed content was not changed. In our case we only display actor's name so we're detecing name's change.

Applying diff result - ActorAdapter.swap()

DiffResult can be applied to adapter by calling diffResult.dispatchUpdatesTo(adapter).

    fun swap(actors: List<Actor>) {
            val diffCallback = ActorDiffCallback(this.actors, actors)
            val diffResult = DiffUtil.calculateDiff(diffCallback)

            this.actors.clear()
            this.actors.addAll(actors)
            diffResult.dispatchUpdatesTo(this)
    }

Resources

License

Copyright 2016 Michał Moczulski

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.

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diffutil-sample's Issues

With duplicated data the sample app crash

Example code:

private static List<Actor> getOriginalActorList() {
        final List<Actor> actors = new ArrayList<>();

        actors.add(new Actor(1, "Jack Nicholson", 10, 1937));
        actors.add(new Actor(2, "Marlon Brando", 9, 1924));
        actors.add(new Actor(3, "Robert De Niro", 8, 1943));
        actors.add(new Actor(4, "Al Pacino", 7, 1940));
        actors.add(new Actor(5, "Daniel Day-Lewis", 6, 1957));
        actors.add(new Actor(6, "Dustin Hoffman", 5, 1937));
        actors.add(new Actor(7, "Tom Hanks", 4, 1956));
        actors.add(new Actor(8, "Anthony Hopkins", 3, 1937));
        actors.add(new Actor(9, "Paul Newman", 2, 1925));
        actors.add(new Actor(10, "Denzel Washington", 1, 1954));
        actors.add(new Actor(1, "Jack Nicholson", 10, 1937));
        actors.add(new Actor(2, "Marlon Brando", 9, 1924));
        actors.add(new Actor(3, "Robert De Niro", 8, 1943));
        actors.add(new Actor(4, "Al Pacino", 7, 1940));
        actors.add(new Actor(5, "Daniel Day-Lewis", 6, 1957));
        actors.add(new Actor(6, "Dustin Hoffman", 5, 1937));
        actors.add(new Actor(7, "Tom Hanks", 4, 1956));
        actors.add(new Actor(8, "Anthony Hopkins", 3, 1937));
        actors.add(new Actor(9, "Paul Newman", 2, 1925));
        actors.add(new Actor(10, "Denzel Washington", 1, 1954));


        return actors;
    }

See I only duplicate the actor entries once, and when you do some changes in the app:

java.lang.IndexOutOfBoundsException: Inconsistency detected. Invalid view holder adapter positionViewHolder{2d2b513b position=20 id=-1, oldPos=11, pLpos:11 scrap [attachedScrap] tmpDetached no parent}
at android.support.v7.widget.RecyclerView$Recycler.validateViewHolderForOffsetPosition(RecyclerView.java:4855)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4986)
at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:4967)
at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2029)
at android.support.v7.widget.LinearLayoutManager.layoutChunk(LinearLayoutManager.java:1414)
at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1377)
at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:578)
at android.support.v7.widget.RecyclerView.dispatchLayoutStep1(RecyclerView.java:3266)
at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3122)
at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:3568)

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