Can I use multiple classes to control one FXML file?

Question

I made an application in Scene Builder on one FXML. I am making a server with JavaFX so I can learn JavaFX and get more familiar with Java's networking libraries.

I have a server terminal Tab and additional tabs within a TabPane. I wanted to make classes that extend upon the main controller class to handle components in each tab.

While trying to implement this I found that the FXMLLoader won't be able to read things if the @FXML annotated variables are static. And the @FXML annotated event listener method won't be read if that is static either.

And if I try any kind of workaround I get nullpointerexceptions when trying to change text in the TextArea. I really don't want to have to use multiple FXML files but it's seeming like I'll have to because if I can't make these static then it just won't work.

Within the Server Terminal Tab there is a TextArea, a TextField, and a Button. Here's my working code:

 package me.Cronin.Keith.JavaServer;

 import java.io.IOException;
 import javafx.application.Application;
 import javafx.fxml.FXML;
 import javafx.fxml.FXMLLoader;
 import javafx.scene.Parent;
 import javafx.scene.Scene;
 import javafx.scene.control.Button;
 import javafx.scene.control.TextArea;
 import javafx.scene.control.TextField;
 import javafx.scene.input.MouseEvent;
 import javafx.stage.Stage;


public class JavaServer extends Application {

@FXML 
public Button btnSendCommand;
@FXML 
public TextField consoleInputField;
@FXML 
public TextArea serverTerminal;

public static FXMLLoader fxmlLoader = new FXMLLoader(JavaServer.class.getResource("JavaServer.fxml"));

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

@Override
public void start(Stage stage) throws IOException
{
    Parent p = fxmlLoader.load();
    Scene scene = new Scene(p);
    stage.setTitle("Java Server v1.0");
    stage.setScene(scene);
    stage.show();
}

@FXML
public void clickSendCommand(MouseEvent event)
{
    serverTerminal.setText("I got clicked..");
}


}

Here's the other class that I don't know what to do with yet:

    package me.Cronin.Keith.JavaServer.Terminal;

    import me.Cronin.Keith.JavaServer.JavaServer;

  public class Terminal extends JavaServer {


  public static void logTerminal(String msg) 
  {

}

}

Is there anything I can do to change this to support what I want to do? I want to be able to control the variables (JavaFX Components from FXML) in JavaServer.class with my other classes that extend upon it.

I have seen this question here: Multiple controller for one FXML file

But it doesn't answer my question.

It's seeming like I'd have to put everything in the main controller class or have multiple Fxml files.

It's not really clear what you're trying to do. The `Application` class should not be a controller. There should be one controller class for each FXML file. If you want different components in different tabs, define an FXML file for each, with a controller class for each FXML file. I don't really see a scenario where the some controller classes would be subclasses of other controller classes. — James_D, Nov 05 '17 at 00:41

Keith Cronin · Answer 1 · 2017-11-05T01:12:55.990

I was able to make this work by replacing my Terminal class with this:

Terminal.java

   package me.Cronin.Keith.JavaServer.Terminal;

   import me.Cronin.Keith.JavaServer.JavaServer;

  public class Terminal extends JavaServer {


      public static void logTerminal(String msg) 
       {
         JavaServer mainController = fxmlLoader.getController();
         mainController.serverTerminal.setText(msg + "\n");
       }

}

So the answer is YES you can.

In JavaServer.java I just called Terminal.class statically and then used the static method logTerminal() within it which worked. I extended JavaServer.java in Terminal.java so I could statically call the controller's FXMLLoader.

Can I use multiple classes to control one FXML file?

1 Answers1