Explain the concept and purpose of widget controllers in user interface development.

In Flutter, widget controllers (e.g., TextEditingController) are used to manage the state and behavior of input widgets such as text fields. They allow:

• To get and set the current input value programmatically.
• To monitor text changes via listeners.
• To control focus and other interaction aspects.

Example of using TextEditingController:

final controller = TextEditingController();

TextField(
  controller: controller,
  onChanged: (text) {
    print('Text changed: $text');
  },
);

// Later, you can get the text:
String currentText = controller.text;

Thus, controllers provide a link between the UI and the application logic, simplifying widget state management.