Jetpack Compose
Google's declarative UI toolkit for Android — describe what the view should look like for a given state, not how to change it.
Traditional Android development meant XML layouts plus code that looked up elements and mutated them. Compose inverts this: the interface is Kotlin functions taking state and returning views. When state changes, the framework re-runs the affected functions and works out what actually needs redrawing.
The model is the same as in React and SwiftUI, and the resemblance is no accident. Compose went stable in 2021 and is now Google's recommended path. Compose Multiplatform, driven by JetBrains, additionally takes the same code to iOS and the desktop.