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

• DiffUtil @ developer.android.com
• "DiffUtil is a must!" @ Medium
• "Diffing Larger Changes" @ Codepath

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.