Question

How do I add event handlers? Specifically buttons

Answer 1

The lab includes this line of code:

btnD4.setOnMouseClicked(evt -> rollDie(4))

OnMouseClicked is an event, and we want to associate a "handler" for it -- i.e. some code that runs whenever the mouse gets clicked within the btnD4 UI widget.

To understand this deeper, Java is technically passing in a new object of a class that implements the EventHandler interface, and includes a method that looks like this:

    btnD4.setOnMouseClicked(new EventHandler<MouseEvent>() {

		@Override
		public void handle(MouseEvent evt) {
			rollDie(4);
			
		}
    });

However, this all gets hidden within the arrow "lambda expression"

(evt -> rollDie(4))

Answer 2

.setOnMouseClicked();