Table of Contents
Introduction
RecyclerView is the standard tool in Android for showing scrollable lists of items. Whether you want to display a list of messages, products, or settings, RecyclerView gives you a powerful and efficient way to do it. This chapter introduces the overall idea of RecyclerView and list based UIs. The detailed setup of adapters and click handling will be covered in the child chapters.
RecyclerView replaces older components like ListView and GridView in modern Android apps. It is more flexible, more efficient, and works well with other Jetpack libraries. Understanding RecyclerView is essential for building practical, real world Android applications.
Why Lists Matter in Android Apps
Many apps are built around collections of data. A chat app shows a list of conversations, a social network shows a feed of posts, and a media app shows a list of songs or videos. Users expect to scroll through these collections smoothly, even when there are hundreds or thousands of items.
You almost never create a separate view for each item manually. Instead, you use a specialized component that handles creating, positioning, recycling, and scrolling item views. RecyclerView does exactly that. It helps you show a list or grid of items while keeping memory usage low and performance high.
From ListView to RecyclerView
Older Android code often used ListView or GridView for lists. RecyclerView was introduced to solve some of the limitations of those components. It is designed to be more modular and customizable. Where ListView combines list behavior and appearance into a single class, RecyclerView separates different responsibilities into smaller pieces.
With RecyclerView, scroll behavior, item animations, and the layout of items are separate and replaceable. This design gives you more control, so the same component can be used for simple lists, complex grids, carousels, and many other layouts.
If you see older tutorials using ListView, you should prefer RecyclerView in new projects. RecyclerView is the recommended solution and is actively improved as part of the Android Jetpack libraries.
Core Concepts of RecyclerView
At the center of this topic is the RecyclerView class itself. You add a RecyclerView to your layout file just like any other view. However, RecyclerView on its own does not know what to display or how many items exist. Instead, it relies on a few key collaborators.
The first collaborator is the adapter. The adapter is responsible for providing the data and creating item views for each position in the list. Later chapters will explain adapters in detail, but at this level it is enough to know that an adapter connects your data model to the RecyclerView UI.
The second collaborator is the layout manager. The layout manager decides how items are arranged on the screen. For example, you can use a layout manager for a vertical list, a horizontal list, or a grid with multiple columns. Because layout managers are separate classes, you can change the layout without changing your data or adapter code.
The third collaborator is the view holder. A view holder is an object that holds references to the views inside one list item layout, such as a TextView for a title or an ImageView for a thumbnail. The view holder makes it cheaper for RecyclerView to reuse existing item views when you scroll.
These three parts, RecyclerView, adapter, and layout manager, work together. RecyclerView controls the scrollable area. The layout manager requests item views for specific positions. The adapter creates and binds those item views. The view holder stores view references so this binding process stays fast.
The Recycling Idea
RecyclerView gets its name from the fact that it recycles item views. When a list has many items, it would be very slow and memory heavy to create a completely new view every time an item appears on the screen. Instead, RecyclerView creates only enough item views to fill the visible space plus a few extra. When you scroll, views that move off screen are reused for new positions that come into view.
This reuse is what makes long lists smooth and efficient. Each list item layout is inflated only a limited number of times, and the data is updated on the same view objects again and again.
The basic life of an item view in RecyclerView looks like this. First, RecyclerView asks the adapter to create a new view holder. Inside that step, the adapter typically inflates a layout and wraps its root view in a view holder object. Next, RecyclerView asks the adapter to bind the view holder to a specific position. The adapter then sets texts, images, and other state based on the data for that position.
Later, when the user scrolls, some view holders are no longer visible. RecyclerView does not destroy them immediately. Instead, it places them into a pool of recycled view holders. When a new position becomes visible, RecyclerView takes a view holder from this pool, if suitable, and asks the adapter to bind it with the data for the new position. This is the recycling mechanism that keeps list performance high.
Basic Usage Flow
Using RecyclerView in an app usually consists of a few clear steps. In your XML layout file, you add a RecyclerView widget. In your activity or fragment, you bring that RecyclerView into your Kotlin code with findViewById or view binding. You then choose and attach a layout manager, for example a linear or grid manager, so RecyclerView knows how to arrange items.
Next, you implement an adapter class. In that adapter, you define a view holder inner class and override required methods to create and bind view holders. Finally, you assign an adapter instance to the RecyclerView. When your data changes, you tell the adapter about the update so the list can refresh.
Later chapters in this section will take you through this process step by step. They will show how to define the adapter and view holder, how to connect them to RecyclerView, and how to handle click events on individual items. For now, it is helpful to know that RecyclerView itself is mostly a container. The interesting logic lives in the adapter and layout manager that you provide.
Layout Options for Lists and Grids
RecyclerView supports different ways to arrange items on the screen, all through separate layout manager classes. The simplest is a linear layout manager. A linear layout manager arranges items in a single column or a single row, which is ideal for classic vertical lists or horizontal carousels.
Another common option is a grid layout manager. A grid layout manager arranges items in rows and columns, which works well for photo galleries, product grids, or icon menus. There is also a staggered grid layout manager that can handle items of varying heights in a masonry style layout.
Because layout managers are separate objects, you can switch from a vertical list to a grid simply by using a different layout manager instance. You do not have to change the RecyclerView itself or your item layouts.
Interaction and Updates
RecyclerView is not only about displaying data. Users will tap on list items, long press them, or swipe them. While this chapter does not cover click handling and interactions in detail, it is important to understand that RecyclerView itself does not handle item clicks. Instead, item click logic is usually implemented in the adapter or inside the view holder.
Updating the data in a RecyclerView is also a key part of real apps. When items are added, removed, or changed, you notify the adapter so that RecyclerView can update the displayed list. Simple refreshes are done with notifyDataSetChanged, and more specific changes can use methods for inserting or deleting individual items, which can also trigger animations.
RecyclerView supports smooth visual updates when the data changes. With the right tools you can calculate differences between old and new lists and apply only the necessary updates. This keeps your UI responsive and avoids heavy redraws.
Performance and Best Practices
RecyclerView is designed for performance, but it still depends on how you use it. The recycling pattern helps, but you must also keep your item layouts reasonable and your binding code efficient. Complex item layouts, heavy image decoding, or expensive operations during binding can still slow down scrolling.
To keep performance high, item layouts should be as simple as possible, and any slow work should be moved off the main thread. Image loading from the network, for example, is usually delegated to a dedicated library that handles background work and caching.
Another important aspect is using the right update methods when your data changes. If you always refresh the entire list, RecyclerView cannot provide fine grained animations and might do more work than necessary. When you inform the adapter about only the exact changes, RecyclerView can reuse views more effectively.
Finally, testing your app on real devices with long lists helps reveal issues such as janky scrolling or slow image loading. RecyclerView gives you the tools for smooth lists, but careful usage and regular testing are still required.
Summary
RecyclerView is the modern foundation for showing dynamic lists and grids in Android apps. It separates concerns into RecyclerView itself as a container, the adapter that connects your data to the UI, the layout manager that arranges items, and the view holder that supports efficient recycling.
In the next chapters, you will create a RecyclerView step by step, learn how to implement adapters and view holders, and handle user interaction with list items. Once you understand these pieces, you will be able to build many types of list based screens that feel fast and professional.