What is the essence of the ViewHolder pattern?

ViewHolder is an auxiliary class in Android designed for caching references to View elements within an adapter.

The essence of the pattern:

1. Caching: Instead of calling findViewById() every time when creating or reusing a list item, ViewHolder finds references to Views once and stores them.
2. Reusing: When scrolling through the list, Android reuses already created View objects to save memory and resources. A ViewHolder attached to such a View provides quick access to its child elements.
3. Performance: Reduces the number of findViewById() calls, significantly speeding up list rendering (e.g., in RecyclerView, ListView).

Example of usage in RecyclerView.Adapter:

class MyAdapter(...) : RecyclerView.Adapter<MyAdapter.MyViewHolder>() {

    inner class MyViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
        val textView: TextView = itemView.findViewById(R.id.my_text_view)
        val imageView: ImageView = itemView.findViewById(R.id.my_image_view)
    }

    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): MyViewHolder {
        val view = LayoutInflater.from(parent.context)
            .inflate(R.layout.list_item_layout, parent, false)
        return MyViewHolder(view) // Create ViewHolder once
    }

    override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
        // Use cached references to update data
        holder.textView.text = "Item ${position}"
        // holder.imageView.setImage...
    }

    // ... other methods
}