Differ In RecyclerView

• RecyclerView is a fundamental component in Android development, widely used to efficiently display large datasets in a scrollable list or grid.

• As the dataset grows or changes, updating the RecyclerView can become a challenging task.

• Manually managing these updates may lead to performance issues and visual glitches.

• Thankfully, Android offers a solution to this problem — the DiffUtils class.

• In this blog, we will explore the power of DiffUtils in conjunction with RecyclerView and understand how it simplifies and optimizes dataset updates.

Understanding DiffUtils:

• DiffUtils is a utility class provided by Android to compute the difference between two lists and generate a list of updates that can be used to efficiently update a RecyclerView’s adapter.

• It compares the old and new datasets, identifies the items that have been added, removed, or modified, and creates a list of changes, often referred to as a “Diff result.

There are two way to implement DiffUtilsclass functionality

ListAdapter  |  API reference  |  Android Developers

RecyclerView.Adapter base class for presenting List data in a RecyclerView, including computing diffs between Lists on a background thread.

https://developer.android.com/reference/androidx/recyclerview/widget/ListAdapter

AsyncListDiffer  |  API reference  |  Android Developers

Helper for computing the difference between two lists via DiffUtil on a background thread.

https://developer.android.com/reference/androidx/recyclerview/widget/AsyncListDiffer

Source Code

1. Create Activity in your project

2. Create activity_main.xml file in layout folder

3. Create a data class

4. Create card_view_design.xml file

5. Implement Adapter Class

• Here we extend ListAdapter<T, YourAdapter.ViewHolder> and implement constructor with a class extending DiffUtil.ItemCallback<T> as a parameter which does the data update calculation for us, which is a bit different when compared with the existing RecyclerView Adapter

• Here we extend ListAdapter and pass TaskDiffCallBack which extends DiffUtilItemCallback<Post>

• This class is a convenience wrapper around AsyncListDiffer that implements Adapter common default behavior for item access and counting.

booksAdapter.submitList(AppUtils.loadData())

• The DiffUtilclass finds the difference between two lists and provides the updated list as an output.

• This class is used to notify updates to a RecyclerView Adapter. Below is the code that let you know how it differentiate data

6. Implementing AsyncListDiffer
• For implementing AsyncListDiffer,we use simple Adapter<BooksAdapter.ViewHolder>() adapter

• In above code we create instance of callback

private val differCallback = object : DiffUtil.ItemCallback<ItemsViewModel>() {
    override fun areItemsTheSame(oldItem: ItemsViewModel, newItem: ItemsViewModel): Boolean {
        return oldItem.id == newItem.id
    }

    override fun areContentsTheSame(oldItem: ItemsViewModel, newItem: ItemsViewModel): Boolean {
        return oldItem == newItem
    }

}

private val differ = AsyncListDiffer(this, differCallback)

• it provides some extra benefits over ListAdapter.

• It can be connected to a RecyclerView.Adapter, and will signal the adapter of changes between submitted lists.

• For simplicity, the ListAdapter wrapper class can often be used instead of the AsyncListDiffer directly. This AsyncListDiffer can be used for complex cases, where overriding an adapter base class to support asynchronous List diffing isn't convenient.

• The AsyncListDiffer can consume the values from a LiveData of List and present the data simply for an adapter. It computes differences in list contents via DiffUtil on a background thread as new Lists are received.

• Use getCurrentList to access the current List, and present its data objects. Diff results will be dispatched to the ListUpdateCallbackimmmediately before the current list is updated. If you're dispatching list updates directly to an Adapter, this means the Adapter can safely access list items and total size via getCurrentList

7. Create a AppUtils class to generate books data

Why Use DiffUtils with RecyclerView:

1. Improved Performance: When dealing with a large dataset, manually notifying the RecyclerView of every individual change can be costly and time-consuming. DiffUtils significantly improves performance by efficiently identifying only the necessary changes and updating only the affected items. This optimization leads to smoother scrolling and an enhanced user experience.

2. No need to use notifyDataSetChanged

3. Internally it calls DiffUtil.calculateDiff which does the handling for us

4. it Makes all calculations on background Thread

5. Seamless Animations: DiffUtils allows RecyclerView to animate the changes smoothly. When items are added, removed, or updated, the RecyclerView gracefully animates the transitions, providing a visually appealing and polished feel to the user interface.

6. Reduced Memory Consumption: Manually handling dataset updates may lead to memory leaks or unnecessary memory consumption. DiffUtils ensures that only the relevant changes are updated, reducing the memory footprint of the application and promoting better memory management.

How to Use DiffUtils in RecyclerView in Kotlin

Have you ever used Android to make a list? What materials did you use? There are two sorts of views: list and recycler. You've probably used RecyclerView before if you're an Android developer. This video will show you how to use DiffUtils to update the RecyclerView. RecyclerView is a term that refers to a view that allows you to recycle items. ListView has been replaced with RecyclerView, which is more flexible and efficient. It's a container for presenting a bigger data set of views that can be swiftly browsed and regenerated. Let's look at the RecyclerView implementation before we go on to Diff Util. Github Source : https://github.com/ezatpanah/DiffUtils-Youtube ✨ Join Medium to read thousands of valuable stories ✨ https://medium.com/@ezatpanah/membership If you're looking to enhance your Android skills or have any questions about the field, feel free to reach out to me on MentorCruise. I'm here to support your growth and learning! Let's connect and learn together! 📚💡 https://mentorcruise.com/mentor/reyhanehezatpanah/

https://www.youtube.com/watch?v=BI95pNokksU

package com.example.notemvvmapp.data.adapter

import android.app.Activity
import android.view.LayoutInflater
import android.view.ViewGroup
import androidx.navigation.findNavController
import androidx.recyclerview.widget.AsyncListDiffer
import androidx.recyclerview.widget.DiffUtil
import androidx.recyclerview.widget.RecyclerView
import com.example.notemvvmapp.data.model.Note
import com.example.notemvvmapp.databinding.NoteLayoutBinding
import com.example.notemvvmapp.presentation.fragment.HomeFragmentDirections

class NoteAdapter(val activity: Activity) : RecyclerView.Adapter<NoteAdapter.MyViewHolder>() {

    class MyViewHolder(val binding: NoteLayoutBinding) : RecyclerView.ViewHolder(binding.root)

    private val differCallback = object : DiffUtil.ItemCallback<Note>() {

        override fun areItemsTheSame(oldItem: Note, newItem: Note): Boolean {
            return oldItem.id == newItem.id &&
                    oldItem.noteTitle == newItem.noteTitle &&
                    oldItem.noteDescription == newItem.noteDescription &&
                    oldItem.modifyDate == newItem.modifyDate &&
                    oldItem.createDate == newItem.createDate
        }

        override fun areContentsTheSame(oldItem: Note, newItem: Note): Boolean {
            return oldItem == newItem
        }
    }

    val differ = AsyncListDiffer(this, differCallback)

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        return MyViewHolder(
            NoteLayoutBinding.inflate(
                LayoutInflater.from(parent.context),
                parent, false
            )
        )
    }

    override fun getItemCount(): Int = differ.currentList.size

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {

        val currentNote = differ.currentList[position]

        holder.binding.noteTitle.text = currentNote.noteTitle
        holder.binding.noteDesc.text = currentNote.noteDescription

        holder.itemView.setOnClickListener {
            val direction = HomeFragmentDirections.actionHomeFragmentToEditNoteFragment(currentNote)
            it.findNavController().navigate(direction)
        }
    }
}

private fun searchNote(query: String?) {

    val searchQuery = "%$query"
    
    noteViewModel.searchNote(searchQuery).observe(this) { notes ->
        
        rvAdapter.differ.submitList(notes)
        
    }
}


// method that will return LiveData of List<Note> 
// observer will notify differ by providing new List 
// differ will compare and list and change Ui Item accordingly