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Graphical User Interfaces ​

Java toolkits for GUIS ​

  • Abstract Windowing Toolkit (AWT)

    • In principle portable
    • java wrappers around native platform libraries.
    • too much original behavior -> protability was lost.

  • Swing

    • Part of JFC java foundation classes.
    • Complete java GUI ues only native canvas, and draws java components onto it.

  • JavaFX

    • software platform for creating and delivering desktop applications
    • brings desktop applications closer to IRAs (Internet Rich Applications) which run on different devices.
    • Developed to replace Swing.
    • Not distributed with JDK 11.

JavaFX ​

Application ​

A class to represent a program with a GUI.

programs should extend Application and implement main() method. In the main method, the application is launched.

Stage and Scene ​

Application gets a Stage with the start() method, which represents a window on the screen (main window of a program)

new windows can be created be creating more Stage objects.

Application needs to fill in and show the main window.

A Stage shows a Scene which is a container for GUI components

Usage:

java
// Pass the scene to the stage and show it
stage.setScene(scene);
stage.setTitle("JavaFX Test");
stage.show();

Visual Example ​

GUI Containers ​

A scene is a container for GUI components. the components placed in scene can themselves be containers, this forms a scene graph

for Example:

null
java
HBox buttonBar = new HBox(20, button1, button2, button3);
buttonBar.setAlignment(Pos.CENTER);

BorderPane root = new BorderPane();
root.setCenter(message);
root.setBottom(buttonBar);

Scene scene = new Scene(root, 450, 200);

JavaFX layouts ​

Event-Driven Programming ​

Events like pressing a button have to be handled. An Event contains information on what happened. An EventHandler handles an Event.

java
Button helloButton = new Button("Say Hello");
helloButton.setOnAction((new EventHandler<ActionEvent>() {
    public void handle(ActionEvent event) {
        System.out.println("Hello World");
    }
}));

EventHandler ​

An EventHandler is a functional interface (defines a single function). handle(Event e), so it can be ued as a target for a lambda expression

java
// lambda expressions
Button helloButton = new Button("Say Hello");
helloButton.setOnAction(e -> System.out.println("Hello World!"));