How to have constructor with arguments for controller?

Question

I would like to have the controller have arguments so that they can be a precondition for the object being constructed and not in setters to be added later on. This will reduce errors.
Unfortunately, fxml only seems to take the no-arg constructor. Is there another way?
Edited by: likejiujitsu on Apr 20, 2013 10:30 AM

Answer 1

Here's perhaps a more realistic example. I have a Main.fxml file with a MainController. The event handler for a button in the Main.fxml file is going to load another fxml file (Dialog.fxml) and display the content in a dialog. The controller associated with Dialog.fxml (DialogController) is going to be initialized by passing a String into the constructor; that String value is retrieved from a text field in Main.fxml.
Main.java:
package example;
import java.io.IOException;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
  @Override
  public void start(Stage primaryStage) throws IOException {
    Parent root = FXMLLoader.load(getClass().getResource("Main.fxml"));
    primaryStage.setScene(new Scene(root, 400, 200));
    primaryStage.show();
  public static void main(String[] args) {
    launch(args);
}Main.fxml:
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.layout.HBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.control.Button?>
<VBox xmlns:fx="http://javafx.com/fxml" spacing="10"
     fx:controller="example.MainController" fx:id="mainRoot">
     <HBox>
          <Label text="Enter text:" />
          <TextField fx:id="textField" />
     </HBox>
     <Button text="Show Dialog" onAction="#showDialog" />
     <!-- TODO Add Nodes -->
</VBox>MainController.java:
package example;
import java.io.IOException;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.stage.Modality;
import javafx.stage.Stage;
import javafx.util.Callback;
public class MainController {
  @FXML
  private TextField textField;
  @FXML
  private Parent mainRoot;
  private final FXMLLoader dialogLoader;
  public MainController() {
    dialogLoader = new FXMLLoader(
        MainController.class.getResource("Dialog.fxml"));
    dialogLoader.setControllerFactory(new Callback<Class<?>, Object>() {
      @Override
      public Object call(Class<?> cls) {
        if (cls == DialogController.class) {
          return new DialogController(textField.getText());
        } else {
          try {
            return cls.newInstance();
          } catch (InstantiationException | IllegalAccessException e) {
            e.printStackTrace();
            throw new RuntimeException(e);
  @FXML
  private void showDialog() throws IOException {
    dialogLoader.setController(null);
    dialogLoader.setRoot(null);
    Parent dialogRoot = (Parent) dialogLoader.load();
    Scene scene = new Scene(dialogRoot, 300, 150);
    Stage dialog = new Stage();
    dialog.initModality(Modality.APPLICATION_MODAL);
    dialog.initOwner(mainRoot.getScene().getWindow());
    dialog.setScene(scene);
    dialog.show();
}Dialog.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.layout.VBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.HBox?>
<VBox xmlns:fx="http://javafx.com/fxml" fx:controller="example.DialogController"
     fx:id="dialogRoot">
     <Label fx:id="label" />
     <HBox>
          <Button text="Click Me" onAction="#click" />
          <Button text="Close" onAction="#close" />
     </HBox>
</VBox>DialogController.java
package example;
import javafx.fxml.FXML;
import javafx.scene.Parent;
import javafx.scene.control.Label;
public class DialogController {
  private final String text;
  @FXML
  private Label label;
  @FXML
  private Parent dialogRoot;
  public DialogController(String text) {
    this.text = text;
  public void initialize() {
    label.setText(text);
  @FXML
  private void click() {
    System.out.println("Text is " + text);
  @FXML
  private void close() {
    dialogRoot.getScene().getWindow().hide();
}Edited by: James_D on Apr 22, 2013 8:00 PM