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In this article, we explored the concepts of composition and recomposition in Android Jetpack Compose. We learned that composition involves combining smaller UI components using composable functions to create complex user interfaces in a modular and reusable manner.

Recomposition is when Jetpack Compose re-executes the composables that may have changed in response to state changes, and then updates the Composition to reflect any changes. A Composition can only be produced by an initial composition and updated by recomposition.

A Compose app is made up of composable functions - just regular functions marked with @Composable , which can call other composable functions. A function is all you need to create a new UI component. The annotation tells Compose to add special support to the function for updating and maintaining your UI over time.

The solution here is to provide item keys. Providing a stable key for each item lets Compose avoid unnecessary recompositions. In this case, Compose can see that the item now at spot 3 is the same item that used to be at spot 2. Since none of the data for that item has changed, Compose doesn't have to recompose it.

The state variable is used to trigger recomposition. Recomposition is essential in Jetpack Compose because Kotlin files are prioritized over XML files. Many Android developers compare the recomposition process to a donut to simplify how it works; a donut has a hole in the center, which is seen as the scope.

Jetpack Compose is a modern declarative UI Toolkit for Android. Compose makes it easier to write and maintain your app UI by providing a declarative API that allows you to render your app UI without imperatively mutating frontend views.

Like most other UI toolkits, Compose renders a frame through several distinct phases. If we look at the Android View system, it has three main phases: measure, layout, and drawing. Compose is very similar but has an important additional phase called composition at the start.

Recomposition is when Jetpack Compose re-executes the composables that may have changed in response to state changes, and then updates the Composition to reflect any changes. A Composition can only be produced by an initial composition and updated by recomposition.