Launch JavaFX application from another class

Question

I need to start a javafx Application from another "container" class and call functions on the Application, but there doesn't seem to be any way of getting hold of a reference to the Application started using the Application.launch() method. Is this possible? Thanks

Answer 1

Suppose this is our JavaFX class:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.stage.Stage;

public class OKButton extends Application {

    @Override
    public void start(Stage stage) {
        Button btn = new Button("OK");
        Scene scene = new Scene(btn, 200, 250);
        stage.setTitle("OK");
        stage.setScene(scene);
        stage.show();
    }
}

Then we may launch it from another class like this:

import javafx.application.Application;

public class Main {
    public static void main(String[] args) {
        Application.launch(OKButton.class, args);
    }
}

Answer 2

I had the same problem as this and got round it using this hack:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

import java.util.concurrent.CountDownLatch;

public class StartUpTest extends Application {
    public static final CountDownLatch latch = new CountDownLatch(1);
    public static StartUpTest startUpTest = null;

    public static StartUpTest waitForStartUpTest() {
        try {
            latch.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return startUpTest;
    }

    public static void setStartUpTest(StartUpTest startUpTest0) {
        startUpTest = startUpTest0;
        latch.countDown();
    }

    public StartUpTest() {
        setStartUpTest(this);
    }

    public void printSomething() {
        System.out.println("You called a method on the application");
    }

    @Override
    public void start(Stage stage) throws Exception {
        BorderPane pane = new BorderPane();
        Scene scene = new Scene(pane, 500, 500);
        stage.setScene(scene);

        Label label = new Label("Hello");
        pane.setCenter(label);

        stage.show();
    }

    public static void main(String[] args) {
        Application.launch(args);
    }
}

and then the class you are launching the application from:

public class StartUpStartUpTest {
    public static void main(String[] args) {
        new Thread() {
            @Override
            public void run() {
                javafx.application.Application.launch(StartUpTest.class);
            }
        }.start();
        StartUpTest startUpTest = StartUpTest.waitForStartUpTest();
        startUpTest.printSomething();
    }
}

Hope that helps you.

Answer 3

Launch JavaFX in other Class using Button:

    class Main extends Application{
      public void start(Stage s)throws Exception{
        event();
        s.show();
      }
      public void event(){
        btn.setOnAction(new EventHandler<ActionEvent>(){
          public void handle(ActionEvent ae){
            Stage s = new Stage();
            new SubClassName().start(s);
          }
        });
      }
      public static void main(String[] args) {
        launch(args);
      }
    }
    class SubClassName{
      public void start(Stage s){
        Pane pane = new Pane();
        Scene addFrame = new Scene(pane,280,450);
        s.setScene(addFrame);     
        s.show();
      }
    }

Answer 4

I'm not sure what you're trying to achieve, but note that you can e.g call from another class Application.launch to start the JavaFX Application thread and Platform.exit to stop it.

Answer 5

The above ways of invoking other javafx class from another sometimes work. Struggling to find an ultimate way to do this brought me to the following walk around:

Suppose this is the javafx class that exteds Application we wish to show from a different class, then we should add the following lines

class ClassToCall extends Application{

  //Create a class field of type Shape preferably static...

  static Stage classStage = new Stage();

  @Override
  public void start(Stage primaryStage){

  // Assign the class's stage object to 
  // the method's local Stage object:

   classStage = primaryStage ;

  // Here comes some more code that creates a nice GUI.....
   // ......
  } 

}

And now from the other place in the project, in order to open the window that the above class creates do the following:

    // Suppose we want to do it with a button clicked:

    btn1.setOnAction(new EventHandler<ActionEvent>() {
        @Override
        public void handle(ActionEvent event) {

           //create an object of the class you wish to invoke its   
            //start() method:

            ClassToCall ctc = new ClassToCall();

          // Then call its start() method in the following way:

            ctc.start(ClassToCall.classStage);


       }// End handle(ActionEvent event)
     });// End anonymous class