OnBindViewHolder does not apply after notifyitemmoved () in Android Recyclerview

Question

The code above is the RecyclerViewAdapter, which changes color only when it is the first item, as shown below.

class TestAdapter : RecyclerView.Adapter<RecyclerView.ViewHolder>() {

private val textColor1 = Color.BLACK
private val textColor2 = Color.YELLOW
private val items = ArrayList<String>()

override fun onBindViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
    val textColor = if(position==0) textColor1 else textColor2
    holder.itemView.textView.setTextColor(textColor)
    holder.itemView.textView.text = items[position]
}

fun move(from:Int,to:Int){
    val item = items[from]
    items.remove(item)
    items.add(to,item)
    notifyItemMoved(from,to)
}
}

In this state I would like to move Value 3 to the first position using the move function. The results I want are shown below.

But in fact, it shows the following results

When using notifyDataSetChanged, I can not see the animation transition effect,

Running the onBindViewHolder manually using findViewHolderForAdapterPosition results in what I wanted, but it is very unstable. (Causing other parts of the error that I did not fix)

fun move(from:Int,to:Int){
    val item = items[from]
    val originTopHolder = recyclerView.findViewHolderForAdapterPosition(0)
    val afterTopHolder = recyclerView.findViewHolderForAdapterPosition(from)
    items.remove(item)
    items.add(to,item)
    notifyItemMoved(from,to)
    if(to==0){
        onBindViewHolder(originTopHolder,1)
        onBindViewHolder(afterTopHolder,0)
    }
}

Is there any other way to solve this?

Answer 1

Using the various notifyItemFoo() methods, like moved/inserted/removed, doesn't re-bind views. This is by design. You could call

if (from == 0 || to == 0) {
    notifyItemChanged(from, Boolean.FALSE);
    notifyItemChanged(to, Boolean.FALSE);
}

in order to re-bind the views that moved.

Answer 2

notifyItemMoved will not update it. According to documentation:

https://developer.android.com/reference/android/support/v7/widget/RecyclerView.Adapter

This is a structural change event. Representations of other existing items in the data set are still considered up to date and will not be rebound, though their positions may be altered.

What you're seeing is expected.

Might want to look into using notifyItemChanged, or dig through the documentation and see what works best for you.