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Event-driven programming •An event is an object created from an event source •You can write code to process events such as a button click, mouse movement, and keystrokes CSE 8B, Spring 2022 3
Event-Driven Programming in Java: • The JVM receives event messages from the OS, and then sends messages to (invokes implemented interface methods of) objects registered for each event.
Event Handlers. An EventHandler<T> is an object that handles events of type T: Event handlers can be registered with nodes that generate events: Note: there can only one. interface EventHandler<T> { void handle(T event); } Scrollbar s = new Scrollbar(); s.setOnScroll(myScrollEventHandler);
event-driven programming: programming paradigm in which the flow of the program is determined by events (e.g. mouse clicks, key presses) event handler: function that is called when a. 5. particular event occurs.
Unlike sequential programs, event-driven programs must work correctly in an environment in which unexpected, dynamic, external stimuli come from sources such as users, hardware, or other processes.
Our simple GUITemperature example has a single event source: myCelsiusField. The GUI Temperature example in Section 7.5 has three event sources: a Celsius field, a Fahrenheit field, a Kelvin field. (The program converts a temp. on any of these scales to the corresponding temperature in the others.) 8.
Classes—or really any code we write (modules, libraries, etc.)—can be thought of from two perspectives. The code for the class itself is called the implementation. For example, all the code we’ve written inside the BubbleGraphics class Slide adapted from Jerry Cain
