12 Matching Annotations
  1. Jan 2021
    1. “Once” handlers Say a button does something pretty darn important, like submitting a payment. It would be pretty scary if it was programmed such that clicking the button multiple times submitted multiple payment requests. It is situations like this where you would attach a click handler to a button that only runs once. To make that clear to the user, we’ll disable the button on click as well.
  2. Dec 2020
    1. A listener watches for an event to be fired. For example, a KeyListener waits for KeyEvents, a MessageListener waits for messages to arrive on a queue and so on. The handler is responsible for dealing with the event. Normally, listeners and handlers go hand-in-hand. For example, the KeyListener tells the ExitHandler that "the letter Q was pressed" and the handler performs logic such as cleaning up resources and exiting the application gracefully. Similary a ButtonClickListener would tell the same ExitHandler that the "Exit button was clicked". So, in this case you have two different events, two different listeners but a single handler.

      You can use the same handler for multiple events/listeners.

    2. The most basic difference is the association Listener is associated with Event Source (Ex: key board) Handler is associated with an Event (Ex: keydown)
  3. Nov 2020
  4. Oct 2020