Android - How to make the recyclerview ListAdpater stop blinking?

user_3131604 0
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I have a recycler view whose adapter uses ListAdapter (version 1.1.0) :

class InnerEpisodeFragmentAdapter(
    private val actCtx: Context,
) : ListAdapter<Episode, InnerEpisodeFragmentAdapter.MViewHolder>(COMPARATOR) {
...

The recycler view is fed by a kotlin flow coming from Room database Episode table :

vm.episodesFlow().asLiveData().observe(viewLifecycleOwner) { episodes ->
  episodes.let { adapter.submitList(it) }
}

@Query("SELECT * FROM Episode ORDER BY pubDate DESC")
fun episodesFlow(): Flow<List<Episode>>

As excepted, each time a tuple changes in Episode table, a new list of episodes is emitted and the recycler view is update.

It works fine, but with an horrible BLINK at each update. It gives a bad user experience.

How can I avoid this blinking when the flow emit new values ?

In the previous version of my app, I used functions like notifyDataSetChanged() or notifyItemChanged() which never blink.I know I could still try to use these functions but I would be very disappointed if I could not avoid the blinks when using the kotlin flow as shown above. Thanks.

android-listadapter kotlin-flow android-recyclerview android
2 Answers

you comparators

areItemsThesame() is wrongly implemented. What you are comparing is reference where is old object and newObject might not same objects. Instead you some use some kind of uuid to compare the two like primary key. If objects are different it will return false and hence areContentsTheSame will never be called otherwise if objects are same their is no point of comparing contents as both oldObject and newObject are pointing to same reference.

Sorry for errors as I am writing from Mobile

user_90462840

======== REQUESTED ADDITIONAL INFORMATION ======

My comparator is fine and does exactly what I want. For example, I want isPlayed to be updated in real time in each recycler view item. And it is. But with a blink of the whole list. The recycler view disappears for a fraction of a second then reappear with the updated info.

companion object {
    private val COMPARATOR = object : DiffUtil.ItemCallback<Episode>() {
        override fun areItemsTheSame(oldItem: Episode, newItem: Episode): Boolean {
            return oldItem === newItem
        }

        override fun areContentsTheSame(oldItem: Episode, newItem: Episode): Boolean {
            return (oldItem.id == newItem.id)
                    && (oldItem.isOnDisk == newItem.isOnDisk)
                    && (oldItem.downloadId == newItem.downloadId)
                    && (oldItem.isPlayed == newItem.isPlayed)
                    && (oldItem.isDeleted == newItem.isDeleted)
        }
    }
}
user_31316040
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