As launch() cannot be called more than once, how do I call, say, a class
public class Graphs extends Application {
more than once? My program runs from a GUI and calls the JavaFX utility with Graph.launch(), and I would like to be able to call the program more than once. How can I do this?
Assuming that you are using Swing in your Java application, to make use of JavaFX, you would not use the application class itself, but rather do the things you do in the Applications start method to construct a JavaFX scenegraph and embed this scene graph inside a Swing JFXPanel.
I made a small example:
import javafx.animation.FadeTransition;
import javafx.animation.RotateTransition;
import javafx.animation.Timeline;
import javafx.application.Platform;
import javafx.embed.swing.JFXPanel;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.util.Duration;
import javax.swing.JButton;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Swing2Test extends JFrame {
public Swing2Test() {
setTitle("Simple example");
JPanel panel = new JPanel();
getContentPane().add(panel);
JButton button = new JButton("Show JavaFX Dialog");
button.setBounds(50, 60, 80, 30);
button.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent event) {
final JDialog dialog = new JDialog(Swing2Test.this,
"JavaFX Dialog",
true);
final JFXPanel contentPane = new JFXPanel();
dialog.setContentPane(contentPane);
dialog.setDefaultCloseOperation(
JDialog.HIDE_ON_CLOSE);
// building the scene graph must be done on the javafx thread
Platform.runLater(new Runnable() {
@Override
public void run() {
contentPane.setScene(createScene());
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
dialog.pack();
dialog.setVisible(true);
}
});
}
});
}
private Scene createScene() {
System.out.println("creating scene");
StackPane root = new StackPane();
Rectangle rect1 = new Rectangle(10, 10, 50, 50);
rect1.setFill(Color.BLUE);
Rectangle rect2 = new Rectangle(0, 0, 30, 30);
rect2.setFill(Color.ORANGE);
root.getChildren().addAll(rect1, rect2);
FadeTransition ft = new FadeTransition(Duration.millis(1800), rect1);
ft.setFromValue(1.0);
ft.setToValue(0.1);
ft.setCycleCount(Timeline.INDEFINITE);
ft.setAutoReverse(true);
ft.play();
RotateTransition rt = new RotateTransition(Duration.millis(1500), rect2);;
rt.setByAngle(180f);
rt.setCycleCount(Timeline.INDEFINITE);
rt.setAutoReverse(true);
rt.play();
return new Scene(root, 150, 150);
}
});
panel.add(button);
setSize(300, 200);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
Swing2Test ex = new Swing2Test();
ex.setVisible(true);
}
});
}
}
You can only launch a single application in a Java Virtual Machine. The Javadoc for the Application::launch() method specifies:
It must not be called more than once or an exception will be thrown.
If your application is a Swing application, you can instead use the technique outlined in Sebastian's answer, similarly a SWT application can use an FXCanvas.
If your application is a JavaFX application that you want to use as a "launcher" for other applications, your launcher could create a new Stage on some signal (e.g. a launch application X button pressed), create a new instance of the target application (using new), and invoke the start method on the target application, passing in the target stage.
