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:
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:
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:
Best Answer
The replacement code you are using via
FXMLLoaderrather than theWebViewcreated scene sample code is fine, you don't need to modify it.Your code will display the main scene for your primary stage based on an fxml document (for my sample I was using a WebView as my main scene, which you don't need, so you don't need any of the WebView related code from the gist).
What you need is some trigger in your controller at the time you want to display a dialog. As a simple example, you can setup an fxml for your main scene which just includes a button, and then supply an ActionHandler for the button in your controller (just like in the Introduction to FXML document).
Now, instead of just doing a println when the button is pressed as Introduction to FXML has, call the
dialog.show()method like the gist did at the time of WebView document load. What should happen is that the dialog will now be displayed on top of your fxml generated scene.You will notice that the dialog itself contains a Scene. If you wanted (and this is optional), you could define the scene contents using fxml. To do this, at the time of dialog construction, you set up a new fxml and new controller for the dialog contents and load the fxml created scene for the dialog into the dialog's stage. The code to do this is pretty much identical code to what you used to load the main scene's fxml into the primaryStage.
Try the above and see if it works for you. If you are still stuck I can probably create an fxml specific example of the gist along the lines of this answer.
Also note that the referenced gist was written a while ago, and there is a now a showAndWait method in JavaFX which facilitates blocking execution of code when making a dialog call and then allowing to process the result of the dialog without using some of the event handler mechanisms from the gist example. Strategies both with and without showAndWait are perfectly acceptable solutions though.