CSC 2040 week 11

CSC 2040: More JavaFX and Events

• Objectives:
  • Describe the underlying architecture of how JavaFX events are processed.
  • Explain how to provide event handlers to manage user interactions.
  • Explain why lambda expressions are preferred over anonymous inner classes.
  • Explain functional interfaces and their use with lambda expressions.

Agenda: Week 11

• Processing Events:

  • Events notify GUI applications of user actions, enabling responses.
  • The JavaFX platform structures event capture, routing, and handling.
  • Each event has a source, target, and type.

• Overview Handling Events:

  • Event handling uses event filters and handlers (implementations of EventHandler interface).
  • Register filters or handlers to notify the application of events.
  • Operating systems capture events and notify listeners.
  • If no listener is registered for an event, it's ignored.

• Types of Events:

  • ActionEvent, MouseEvent, DragEvent, KeyEvent, ScrollEvent, TouchEvent (listed in a hierarchy chart).

• GUI Validation:

  • GUI applications validate user input after events (button clicks, etc.).
  • Avoid popup alerts; instead, use hidden elements (labels, image views) that display error messages or tooltips when an event triggers an error.

• Scene Builder and Event Handling:

  • The module describes common events in JavaFX controls.
  • Setting event handler properties to user-defined event handlers automatically registers them.

• Java Code and Event Handling:

  • ViewController (this): Method limitation for handling multiple events.
  • Private Inner Class: Separates event details into a nested class, explicitly.
  • Anonymous Inner Class: Handles events within registration instructions, but can be less readable for complex scenarios.
  • Lambda Expressions: Uses functional interfaces, developers must understand the underlying API specifics.
  • Delegation Class: Uses a helper class to manage events, separating concerns and providing public access methods.

• Event Handling with Code Example (ViewController): Provides an illustrated example of handling events within the ViewController class, encompassing Initializable and EventHandler interfaces. This includes handling ActionEvent within the class.

• Anonymous in Java:

  • Anonymous objects are nameless.
  • Their usage is limited to single-use scenarios.
  • Anonymous inner classes are nested classes without names, often used for single-instance scenarios.

• Private Inner Class Handles Event: Example of a private inner class inheriting EventHandler<ActionEvent>.

• Anonymous Inner Class Handles Event: Example of an anonymous inner class handling events.

• Lambda -> Event: Demonstrates lambda expressions for handling events with a concise example.

• Delegation Class Handles Event: Demonstrates delegation by passing the view controller object.

• Property Events / AddListener:

  • JavaFX properties have addListener methods for handling property changes.
  • ChangeListener handles recalculated property changes, with previous, current, and new values.
  • InvalidationListener triggers when a property's value becomes unknown.

• TODO: Complete Week 11 Content Module in D2L.

• Pre-work Grade: Post weekly discussion questions/research solutions to D2L.

• Help/Questions:

  • Student Office Hours: Schedule a meeting with Julie.
  • Email: [email protected]
  • RRCC On-Campus Tutoring: Visit the link in the slide.
  • 24/7 Online Tutoring: Utilize the D2L resources.