An activity in Android is a fundamental application component that represents a single screen with which users can interact, similar to a window or frame in desktop applications
. It combines both the user interface design (usually defined in XML files) and the code logic (typically written in Java or Kotlin files) to create a complete screen experience
. Each activity provides a window where the app draws its UI, typically filling the entire screen but can also be smaller or float on top of other windows
. For example, an app might have separate activities for the login screen, home screen, or settings screen
. Activities have a lifecycle managed by the Android system, which includes
states such as creation, start, resume, pause, stop, and destruction.
Developers override lifecycle callback methods like onCreate(), onStart(),
and onResume() to control what happens during these states
. In summary:
- An activity is a screen in an Android app where users interact.
- It is implemented as a subclass of the
Activityclass. - It consists of UI layout files (XML) and code files (Java/Kotlin).
- Activities are declared in the app's manifest file to be recognized by the system.
- Activities manage user interaction and app navigation through lifecycle methods.
- Multiple activities can exist in an app, loosely connected to provide a complete user experience
Thus, an activity is essentially the building block of the user interface in Android apps, managing both what the user sees and how the app responds to user actions.
