JAVAFX BASICS - Introduction to Java Programming: Comprehensive Version - page 540

L ISTING 14.3

ButtonInPane.java
1 import javafx.application.Application;
2 import javafx.scene.Scene;
3 import javafx.scene.control.Button;
4 import javafx.stage.Stage;
5 import javafx.scene.layout.StackPane;
6
7 public class ButtonInPane extends Application {
8 @Override // Override the start method in the Application class
9 public void start(Stage primaryStage) {
10 // Create a scene and place a button in the scene
11 StackPane pane = new StackPane();
12 pane.getChildren().add( new Button( " OK " ));
13 Scene scene = new Scene(pane, 200 , 50 );
14 primaryStage.setTitle( " Button in a pane " ); // Set the stage title
15 primaryStage.setScene(scene); // Place the scene in the stage
16

create a pane
add a button
add pane to scene

primaryStage.show(); // Display the stage display stage

17 }
18 }

main method omitted

F IGURE 14.4

A button is placed in the center of the pane.

The program creates a StackPane (line 11) and adds a button as a child of the pane (line 12).
The getChildren() method returns an instance of javafx.collections.ObservableList .
ObservableList behaves very much like an ArrayList for storing a collection of elements.
Invoking add(e) adds an element to the list. The StackPane places the nodes in the center
of the pane on top of each other. Here, there is only one node in the pane. The StackPane
respects a node's preferred size. So you see the button displayed in its preferred size.
Listing 14.4 gives an example that displays a circle in the center of the pane, as shown in
Figure 14.5a.

ObservableList

L ISTING 14.4

ShowCircle.java
1 import javafx.application.Application;
2 import javafx.scene.Scene;
3 import javafx.scene.layout.Pane;
4 import javafx.scene.paint.Color;
5 import javafx.scene.shape.Circle;
6 import javafx.stage.Stage;
7
8 public class ShowCircle extends Application {
9 @Override // Override the start method in the Application class
10 public void start(Stage primaryStage) {
11 // Create a circle and set its properties
12 Circle circle = new Circle();
13 circle.setCenterX( 100 );
14 circle.setCenterY( 100 );
15 circle.setRadius( 50 );
16 circle.setStroke(Color.BLACK);
17 circle.setFill(Color.WHITE);
18
19

create a circle
set circle properties

// Create a pane to hold the circle

20 Pane pane = new Pane();

create a pane