ViewHolders

A ViewHolder is a design pattern used in Android development, primarily within adapter-backed views such as RecyclerView and ListView. Its main purpose is to improve performance by recycling views as the user scrolls through a list. Instead of creating a new view for each item in the data set, which can be resource-intensive, ViewHolder pattern reuses existing views.

The pattern involves creating a custom class that holds references to the individual views within a list item's layout, such as TextViews, ImageViews, or Buttons. When an item is displayed, the adapter first checks if there is a ViewHolder available for reuse. If so, it uses that ViewHolder to populate the views with the data for the new item. If no ViewHolder is available, a new one is created, and its views are inflated and populated. The ViewHolder is then attached to the view.

This approach significantly reduces the number of times `findViewById()` is called, which is a relatively slow operation. It also minimizes the overhead associated with inflating new layouts. As a result, scrolling becomes much smoother, especially for lists with a large number of items. The ViewHolder pattern is a fundamental optimization for efficient list display in Android applications.