JavaFX 2.0 + FXML. Updating scene values from a different Task

fxmljavajavafx-2

I want to get the controller from a scene that i've loaded with FXMLoader. The use case is:

My JSON manager receives a JSON object

The task I've launched shows a new Scene using

Parent p = FXMLLoader.load(getClass().getResource("foo.fxml"));
Scene scene = new Scene(p);
stage.setScene(scene);

After that, i have the empty scene.

Now I do this to fill the components

AnchorPane pane = (AnchorPane)((AnchorPane) scene.getRoot()).getChildren().get(0);
for(Node node : pane.getChildren()){
    String id = node.getId();
    if(id.equals(NAME)){
         ((TextField)node).setText(value);
    }
}

My question, is there an easier way to do this? I have a controller specified in FXML

<AnchorPane id="AnchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="526.0" minWidth="356.0" prefHeight="526.0" prefWidth="356.0" 
xmlns:fx="http://javafx.com/fxml" fx:controller="bar.foo">

I want to get the instance with the bind values (TextField called name in this case)

Thanks in advance

Best Answer

1) You can get the controller from the FXMLLoader but don't know is it possible from Scene :

FXMLLoader fxmlLoader = new FXMLLoader();
Pane p = fxmlLoader.load(getClass().getResource("foo.fxml").openStream());
bar.foo fooController = (bar.foo) fxmlLoader.getController();

To use the fooController later in a different part of your code, you can use Node#setUserData(). For example after the code above:

p.setUserData(fooController);
...
// after a while of app logic and code
bar.foo controller_of_p = (bar.foo) p.getUserData();

This gives a workaround and a shortcut to achieve your goal.

2) If your node has an id then you can directly Node#lookup() it rather than constructing a for-loop :

TextField txt = (TextField) pane.lookup("#nodeId");

Related Solutions

How to create custom components in JavaFX 2.0 using FXML

Update: For an up-to-date tutorial, please, consult the official documentation. There was a lot of new stuff that was added in 2.2. Also, the Introduction to FXML covers pretty much everything you need to know about FXML. Finally, Hendrik Ebbers made an extremely helpful blog post about custom UI controls.

After a few days of looking around the API and reading through some docs (Intro to FXML, Getting started with FXML Property binding, Future of FXML) I've come up with a fairly sensible solution. The least straight-forward piece of information I learned from this little experiment was that the instance of a controller (declared with fx:controller in FXML) is held by the FXMLLoader that loaded the FXML file... Worst of all, this important fact is only mentioned in one place in all the docs I saw:

a controller is generally only visible to the FXML loader that creates it

So, remember, in order to programmatically (from Java code) obtain a reference to the instance of a controller that was declared in FXML with fx:controller use FXMLLoader.getController() (refer to the implementation of the ChoiceCell class below for a complete example).

Another thing to note is that Property.bindBiderctional() will set the value of the calling property to the value of the property passed in as the argument. Given two boolean properties target (originally set to false) and source (initially set to true) calling target.bindBidirectional(source) will set the value of target to true. Obviously, any subsequent changes to either property will change the other property's value (target.set(false) will cause the value of source to be set to false):

BooleanProperty target = new SimpleBooleanProperty();//value is false
BooleanProperty source = new SimpleBooleanProperty(true);//value is true
target.bindBidirectional(source);//target.get() will now return true
target.set(false);//both values are now false
source.set(true);//both values are now true

Anyway, here is the complete code that demonstrates how FXML and Java can work together (as well as a few other useful things)

Package structure:

com.example.javafx.choice
  ChoiceCell.java
  ChoiceController.java
  ChoiceModel.java
  ChoiceView.fxml
com.example.javafx.mvc
  FxmlMvcPatternDemo.java
  MainController.java
  MainView.fxml
  MainView.properties

FxmlMvcPatternDemo.java

package com.example.javafx.mvc;

import java.util.ResourceBundle;
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class FxmlMvcPatternDemo extends Application
{
    public static void main(String[] args) throws ClassNotFoundException
    {
        Application.launch(FxmlMvcPatternDemo.class, args);
    }

    @Override
    public void start(Stage stage) throws Exception
    {
        Parent root = FXMLLoader.load
        (
            FxmlMvcPatternDemo.class.getResource("MainView.fxml"),
            ResourceBundle.getBundle(FxmlMvcPatternDemo.class.getPackage().getName()+".MainView")/*properties file*/
        );

        stage.setScene(new Scene(root));
        stage.show();
    }
}

MainView.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<VBox
    xmlns:fx="http://javafx.com/fxml"
    fx:controller="com.example.javafx.mvc.MainController"

    prefWidth="300"
    prefHeight="400"
    fillWidth="false"
>
    <children>
        <Label text="%title" />
        <ListView fx:id="choicesView" />
        <Button text="Force Change" onAction="#handleForceChange" />
    </children>
</VBox>

MainView.properties

title=JavaFX 2.0 FXML MVC demo

MainController.java

package com.example.javafx.mvc;

import com.example.javafx.choice.ChoiceCell;
import com.example.javafx.choice.ChoiceModel;
import java.net.URL;
import java.util.ResourceBundle;
import javafx.collections.FXCollections;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ListCell;
import javafx.scene.control.ListView;
import javafx.util.Callback;

public class MainController implements Initializable
{
    @FXML
    private ListView<ChoiceModel> choicesView;

    @Override
    public void initialize(URL url, ResourceBundle rb)
    {
        choicesView.setCellFactory(new Callback<ListView<ChoiceModel>, ListCell<ChoiceModel>>()
        {
            public ListCell<ChoiceModel> call(ListView<ChoiceModel> p)
            {
                return new ChoiceCell();
            }
        });
        choicesView.setItems(FXCollections.observableArrayList
        (
            new ChoiceModel("Tiger", true),
            new ChoiceModel("Shark", false),
            new ChoiceModel("Bear", false),
            new ChoiceModel("Wolf", true)
        ));
    }

    @FXML
    private void handleForceChange(ActionEvent event)
    {
        if(choicesView != null && choicesView.getItems().size() > 0)
        {
            boolean isSelected = choicesView.getItems().get(0).isSelected();
            choicesView.getItems().get(0).setSelected(!isSelected);
        }
    }
}

ChoiceView.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import java.lang.*?>
<?import javafx.scene.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>

<HBox
    xmlns:fx="http://javafx.com/fxml"

    fx:controller="com.example.javafx.choice.ChoiceController"
>
    <children>
        <CheckBox fx:id="isSelectedView" />
        <Label fx:id="labelView" />
    </children>
</HBox>

ChoiceController.java

package com.example.javafx.choice;

import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.CheckBox;
import javafx.scene.control.Label;

public class ChoiceController
{
    private final ChangeListener<String> LABEL_CHANGE_LISTENER = new ChangeListener<String>()
    {
        public void changed(ObservableValue<? extends String> property, String oldValue, String newValue)
        {
            updateLabelView(newValue);
        }
    };

    private final ChangeListener<Boolean> IS_SELECTED_CHANGE_LISTENER = new ChangeListener<Boolean>()
    {
        public void changed(ObservableValue<? extends Boolean> property, Boolean oldValue, Boolean newValue)
        {
            updateIsSelectedView(newValue);
        }
    };

    @FXML
    private Label labelView;

    @FXML
    private CheckBox isSelectedView;

    private ChoiceModel model;

    public ChoiceModel getModel()
    {
        return model;
    }

    public void setModel(ChoiceModel model)
    {
        if(this.model != null)
            removeModelListeners();
        this.model = model;
        setupModelListeners();
        updateView();
    }

    private void removeModelListeners()
    {
        model.labelProperty().removeListener(LABEL_CHANGE_LISTENER);
        model.isSelectedProperty().removeListener(IS_SELECTED_CHANGE_LISTENER);
        isSelectedView.selectedProperty().unbindBidirectional(model.isSelectedProperty())
    }

    private void setupModelListeners()
    {
        model.labelProperty().addListener(LABEL_CHANGE_LISTENER);
        model.isSelectedProperty().addListener(IS_SELECTED_CHANGE_LISTENER);
        isSelectedView.selectedProperty().bindBidirectional(model.isSelectedProperty());
    }

    private void updateView()
    {
        updateLabelView();
        updateIsSelectedView();
    }

    private void updateLabelView(){ updateLabelView(model.getLabel()); }
    private void updateLabelView(String newValue)
    {
        labelView.setText(newValue);
    }

    private void updateIsSelectedView(){ updateIsSelectedView(model.isSelected()); }
    private void updateIsSelectedView(boolean newValue)
    {
        isSelectedView.setSelected(newValue);
    }
}

ChoiceModel.java

package com.example.javafx.choice;

import javafx.beans.property.BooleanProperty;
import javafx.beans.property.SimpleBooleanProperty;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;

public class ChoiceModel
{
    private final StringProperty label;
    private final BooleanProperty isSelected;

    public ChoiceModel()
    {
        this(null, false);
    }

    public ChoiceModel(String label)
    {
        this(label, false);
    }

    public ChoiceModel(String label, boolean isSelected)
    {
        this.label = new SimpleStringProperty(label);
        this.isSelected = new SimpleBooleanProperty(isSelected);
    }

    public String getLabel(){ return label.get(); }
    public void setLabel(String label){ this.label.set(label); }
    public StringProperty labelProperty(){ return label; }

    public boolean isSelected(){ return isSelected.get(); }
    public void setSelected(boolean isSelected){ this.isSelected.set(isSelected); }
    public BooleanProperty isSelectedProperty(){ return isSelected; }
}

ChoiceCell.java

package com.example.javafx.choice;

import java.io.IOException;
import java.net.URL;
import javafx.fxml.FXMLLoader;
import javafx.fxml.JavaFXBuilderFactory;
import javafx.scene.Node;
import javafx.scene.control.ListCell;

public class ChoiceCell extends ListCell<ChoiceModel>
{
    @Override
    protected void updateItem(ChoiceModel model, boolean bln)
    {
        super.updateItem(model, bln);

        if(model != null)
        {
            URL location = ChoiceController.class.getResource("ChoiceView.fxml");

            FXMLLoader fxmlLoader = new FXMLLoader();
            fxmlLoader.setLocation(location);
            fxmlLoader.setBuilderFactory(new JavaFXBuilderFactory());

            try
            {
                Node root = (Node)fxmlLoader.load(location.openStream());
                ChoiceController controller = (ChoiceController)fxmlLoader.getController();
                controller.setModel(model);
                setGraphic(root);
            }
            catch(IOException ioe)
            {
                throw new IllegalStateException(ioe);
            }
        }
    }
}

Passing Parameters JavaFX FXML

Using MVC

Most of this answer focuses on a direct call to pass a parameter from a calling class to the controller.

If instead, you want to decouple the caller and controller and use a more general architecture involving a model class with settable and listenable properties to achieve inter-controller communication, see the following basic overview:

Applying MVC With JavaFx

Recommended Approach

This answer enumerates different mechanisms for passing parameters to FXML controllers.

For small applications I highly recommend passing parameters directly from the caller to the controller - it's simple, straightforward and requires no extra frameworks.

For larger, more complicated applications, it would be worthwhile investigating if you want to use Dependency Injection or Event Bus mechanisms within your application.

Passing Parameters Directly From the Caller to the Controller

Pass custom data to an FXML controller by retrieving the controller from the FXML loader instance and calling a method on the controller to initialize it with the required data values.

Something like the following code:

public Stage showCustomerDialog(Customer customer) {
  FXMLLoader loader = new FXMLLoader(
    getClass().getResource(
      "customerDialog.fxml"
    )
  );

  Stage stage = new Stage(StageStyle.DECORATED);
  stage.setScene(
    new Scene(loader.load())
  );

  CustomerDialogController controller = loader.getController();
  controller.initData(customer);

  stage.show();

  return stage;
}

...

class CustomerDialogController {
  @FXML private Label customerName;
  void initialize() {}
  void initData(Customer customer) {
    customerName.setText(customer.getName());
  }
}

A new FXMLLoader is constructed as shown in the sample code i.e. new FXMLLoader(location). The location is a URL and you can generate such a URL from an FXML resource by:

new FXMLLoader(getClass().getResource("sample.fxml"));

Be careful NOT to use a static load function on the FXMLLoader, or you will not be able to get your controller from your loader instance.

FXMLLoader instances themselves never know anything about domain objects. You do not directly pass application specific domain objects into the FXMLLoader constructor, instead you:

Construct an FXMLLoader based upon fxml markup at a specified location
Get a controller from the FXMLLoader instance.
Invoke methods on the retrieved controller to provide the controller with references to the domain objects.

This blog (by another writer) provides an alternate, but similar, example.

Setting a Controller on the FXMLLoader

CustomerDialogController dialogController = 
    new CustomerDialogController(param1, param2);

FXMLLoader loader = new FXMLLoader(
    getClass().getResource(
        "customerDialog.fxml"
    )
);
loader.setController(dialogController);

Pane mainPane = loader.load();

You can construct a new controller in code, passing any parameters you want from your caller into the controller constructor. Once you have constructed a controller, you can set it on an FXMLLoader instance before you invoke the load() instance method.

To set a controller on a loader (in JavaFX 2.x) you CANNOT also define a fx:controller attribute in your fxml file.

Due to the limitation on the fx:controller definition in FXML, I personally prefer getting the controller from the FXMLLoader rather than setting the controller into the FXMLLoader.

Having the Controller Retrieve Parameters from an External Static Method

This method is exemplified by Sergey's answer to Javafx 2.0 How-to Application.getParameters() in a Controller.java file.

Use Dependency Injection

FXMLLoader supports dependency injection systems like Guice, Spring or Java EE CDI by allowing you to set a custom controller factory on the FXMLLoader. This provides a callback that you can use to create the controller instance with dependent values injected by the respective dependency injection system.

An example of JavaFX application and controller dependency injection with Spring is provided in the answer to:

Adding Spring Dependency Injection in JavaFX (JPA Repo, Service)

A really nice, clean dependency injection approach is exemplified by the afterburner.fx framework with a sample air-hacks application that uses it. afterburner.fx relies on JEE6 javax.inject to perform the dependency injection.

Use an Event Bus

Greg Brown, the original FXML specification creator and implementor, often suggests considering use of an event bus, such as the Guava EventBus, for communication between FXML instantiated controllers and other application logic.

The EventBus is a simple but powerful publish/subscribe API with annotations that allows POJOs to communicate with each other anywhere in a JVM without having to refer to each other.

Follow-up Q&A

on first method, why do you return Stage? The method can be void as well because you already giving the command show(); just before return stage;. How do you plan usage by returning the Stage

It is a functional solution to a problem. A stage is returned from the showCustomerDialog function so that a reference to it can be stored by an external class which may wish to do something, such as hide the stage based on a button click in the main window, at a later time. An alternate, object-oriented solution could encapsulate the functionality and stage reference inside a CustomerDialog object or have a CustomerDialog extend Stage. A full example for an object-oriented interface to a custom dialog encapsulating FXML, controller and model data is beyond the scope of this answer, but may make a worthwhile blog post for anybody inclined to create one.

Additional information supplied by StackOverflow user named @dzim

Example for Spring Boot Dependency Injection

The question of how to do it "The Spring Boot Way", there was a discussion about JavaFX 2, which I anserwered in the attached permalink. The approach is still valid and tested in March 2016, on Spring Boot v1.3.3.RELEASE: https://stackoverflow.com/a/36310391/1281217

Sometimes, you might want to pass results back to the caller, in which case you can check out the answer to the related question:

JavaFX FXML Parameter passing from Controller A to B and back

Best Answer

Related Solutions

How to create custom components in JavaFX 2.0 using FXML

Passing Parameters JavaFX FXML

Related Topic