Keep in mind that singletons are not a data persistence solution. To share logic that doesn’t have associated state throughout the app.To share data between two otherwise unrelated areas of your project.A singleton’s two most common use cases are:

A singleton is a design pattern in which a given class has only one single instance inside the entire app. Using Singletons in Kotlinīy using the keyword object in your app, you’re defining a singleton. For details about Kotlin extensions, check out our Extension Functions and Properties Tutorial. Note: For more details about RecyclerView, read our Android RecyclerView Tutorial. Keep reading to implement this shopping experience while learning about the many uses for the object keyword in Kotlin. However, you can’t buy anything just yet. You’ll see a screen with a variety of Android-themed products for sale:

StringUtils.kt: Contains a handy extension on Int to format it to a price string like $12.34.

ShoppingCartActivity.kt: An activity you’ll use to display the user’s shopping cart, total price and a button to clear the cart.

ProductListAdapter.kt: A ListAdapter, which both MainActivity and ShoppingCartActivity use to populate a RecyclerView of products.

Product.kt: A model representing a product in the store.

MainActivity.kt: Your app’s initial screen.

When you open the starter project, you’ll see some structure already in place: Select Open an Existing Project and then select the name of the starter project. Open your project in Android Studio 4.1 or higher. Getting Startedĭownload the starter project by clicking the Download Materials button at the top or bottom of the tutorial. If you’d like to revisit the basics of Kotlin, consider reading Kotlin for Android: An Introduction.

Note: This tutorial assumes familiarity with Kotlin for Android development.

Kotlin weak reference