JavaFX : Adding a new node to Scene in java code when Scene is initially loaded from FXML

Question

How can I add a new node to the Scene in java code when Scene is initially loaded from FXML ? I have loaded from FXML as shown below

Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));

Scene scene = new Scene(root, 1000, 600, Color.DODGERBLUE);

Now say for example how do I add button to the scene in Java code?

Answer 1

I do not know the reason behind your question. If what you want is to insert some nodes dynamically during the application or scene initialization, I suggest you use a initialize method at your controller.

This method must be annotated with @FXML and have the following signature:

void initialize()

Then, you can inject the container where the button must be inserted on the controller and add the button to it:

@FXML
HBox buttonBox // assuming your button container is a HBox
...

@FXML
protected void initialize() {
    buttonBox.getChildren().add(new Button("Click me!"));
}

The method initialize is called after the components defined at the FXML file were built.

Answer 2

Here is one way to do this:

((VBox) root).getChildren().add(new Button("Java Button"));

The snippet above assumes that the top container defined in your FXML is a VBox, if it is not a VBox, just cast it to whatever type you have chosen.

I wonder how I can determine the type of the container at runtime, so I can write a more generic code.

The type is likely a Pane, so casting to a Pane will work in most cases. Using a layout Pane as a Parent is usually recommended for most layout tasks in JavaFX.