An Activity in Android is a fundamental application component that represents a single screen with which a user can interact. It provides the window or UI where the app draws its content, similar to a window or frame in desktop applications
Key Points about Activity in Android:
- Role : An activity is essentially one screen of an app. For example, a login screen, home screen, or settings screen in an app are typically implemented as separate activities
- Lifecycle : Activities have a lifecycle managed by the Android system with specific callback methods such as
onCreate(),onStart(),onResume(),onPause(),onStop(), andonDestroy(). These callbacks allow the app to handle transitions between different states, like when the activity is created, becomes visible, or is destroyed
- Entry Point : When an app is launched, the system starts a designated main activity. Activities can also start other activities within the same or different apps, enabling navigation and interaction between different screens or apps
- Implementation : Activities are implemented as subclasses of the
Activityclass in Java or Kotlin. The UI design is typically defined in XML files, while the behavior and logic are coded in the corresponding Java/Kotlin files
- Interaction : Activities serve as the presentation layer of an Android app. They handle user input and display UI elements. They are loosely coupled, meaning one activity can start another without tight dependencies
- Modern Usage : Traditionally, apps had one activity per screen, but with newer architectures like Jetpack Compose, apps often use a single activity hosting multiple composable UI screens
Summary
An Android activity is a core building block that represents a screen in an app, managing UI and user interaction through a well-defined lifecycle, and serving as the entry point for user engagement with the app
