What is BuildContext in Flutter and how is it used?

BuildContext is a handle that points to the location of a widget in the widget tree. Each widget has its own BuildContext.

It is used:

• To access data from ancestors: For example, Theme.of(context) to get the current theme.
• To find ancestor widgets: Navigator.of(context) for navigation.
• To perform context-dependent actions: Displaying a SnackBar via ScaffoldMessenger.of(context).
• To get the size and position of a widget: Using BuildContext.size or BuildContext.findRenderObject().

Example:

// Accessing ThemeData
ThemeData theme = Theme.of(context);

// Navigation
Navigator.push(
  context,
  MaterialPageRoute(builder: (context) => NextScreen()),
);

// Displaying SnackBar
ScaffoldMessenger.of(context).showSnackBar(
  SnackBar(content: Text('Hello')),
);

BuildContext is only valid during the lifecycle of the corresponding widget.