Lesson 19: JavaFX

JavaFX Basics and Hello World:

• Isn’t part of the Java Standard Library
  • Must be included when running a JavaFX program
• The window of the GUI is called the stage
• The data inside of the window is called the scene
• Must extend the application class
• Must have the start method
  • Preforms the setup needed to create the JavaFX application
• The start method is then called by launch, which organizes the stage and scene
  • Must be created and passes in a Stage parameter
• A main method is not needed
  • Java automatically creates a state to pass into start
• Hello World:

  //Imports
  import javafx.application.Application;
  import javafx.event.ActionEvent;
  import javafx.event.EventHandler;
  import javafx.scene.Scene;
  import javafx.scene.control.Button;
  import javafx.scene.layout.StackPane;
  import javafx.stage.Stage;
   
  //Extends Application
  public class HelloWorld extends Application {
   
      public static void main(String[] args) {
          launch(args); //Runs start method
      }
   
      public void start(Stage mainStage) {
          mainStage.setTitle("Hello World Program"); //Title of window
   
          Button btn = new Button(); //Creating button
          btn.setText("Print Hello World!"); //Setting text of button
          btn.setOnAction(new CustomEventHandler()); //Runs CustomEventHandler() method
   
          StackPane root = new StackPane(); //Creates new StackPane
          root.getChildren().add(btn); //Add button to the StackPane
   
          Scene scene = new Scene(root, 300, 300); //Creating new Scene
          mainStage.setScene(scene); //Sets the created scene to the stage
          mainStage.show(); //Displays the stage
      }
   
      
      private class CustomEventHandler implements EventHandler<ActionEvent> {
          public void handle(ActionEvent event) {
              System.out.println("Hello World!"); //Prints to terminal
          }
      }
  } 

The Stage and Scenes:

• Stage
  • Only one
  • The window of the app
  • Contains all of the displayed data
• Scenes
  • Multiple
  • The content being displayed on stage

Event Handling:

• Clicking a button creates an ActionEvent object that contains the actions of the user
• ActionEvent is a child class of Event
• ActionEvent fires an EventHandler object that has a handle method which runs the expected behavior
• Every EventHandler class must implement EventHandler
• Functional Interface: An interface with only one abstract method
• Some other events:
  • WindowEvent
  • InputEvent
    • KeyEvent
    • MouseEvent
    • TouchEvent

List of Node Types:

• Layouts: FlowPlane, GridPlane, BorderPlane, HBox, StackPlane, VBox
• Shapes: Circle, Rectangle
• Images: Imageview
• Controls: Button, CheckBox, TextField, Label
• Root Node: The node at the top of the scene graph
• Leaf Node: Any Nodes that are below the root node

Scene Graph and Stack Pane:

• The scene graph is used to show the hierarchy of nodes inside of the stack pane

Anonymous Inner Classes:

• Classes that are used for one specific case
• More concise then writing an entire class
• Don’t have a name

// Can remove eventname if used directly
EventHandler<ActionEvent> eventName = new EventHandler<>() {
  public void handle(ActionEvent event) {
    //Action
  }
}

Lambda Expressions:

• Even more concise then Anonymous Inner Classes

//Same as code above
((ActionEvent event) -> {
  //Action
}
 
//Another example
event -> //Action