How do I fit a JavaFX Pane to the size of its contents? - javafx

Question

In JavaFX, I see lots of examples of how to make a child component extend its size to fit the parent pane. But I can't see how to shrink the parent pane to fit the size of its child contents.
In the following example, I create a Stage with a Scene of size 500x500 pixels. Inside that Scene is a VBox that has one child, a single Label.
I'd like the VBox Pane to be the size of the Label, not the size of the whole Stage. (In a more complex application, I'm making the VBox a draggable Pane, so I want it to be just big enough to fit its contents).
How can I do that?
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class Sample extends Application {
public static void main(String[] args) {
launch(args);
}
#Override
public void start(Stage primaryStage) throws Exception {
VBox vbox = new VBox();
vbox.setStyle("-fx-background-color: #efecc2");
vbox.setPrefSize(100, 100);
Label label = new Label("Label");
label.setStyle("-fx-background-color: lightcyan");
vbox.getChildren().add(label);
Scene scene = new Scene(vbox, 500, 300);
primaryStage.setScene(scene);
primaryStage.show();
}
}
As you can see in the picture below, the label (with a blue background) is small, but the VBox (with a yellow background) fills the whole window. It doesn't seem to matter that I set the preferred size of the VBox to 100,100: it still fills up the whole 500 x 300 pixel Scene.
How can I tell the VBox to be only as big as the Label that is inside of it? (Or, when I add, say, 3 things inside it, to be as big as those?)

Answer 1

First problem here is a scene's root object. It will always be the same size as the scene. So you need to add the parent Pane as root element and then add VBox into it.
Second problem is a type of Pane. Some elements affect the size of children(BorderPane, StackPane), some not (Pane, AnchorPane). So you need to choose the right parent.
Here is a simple example:
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class Sample extends Application {
#Override
public void start(Stage primaryStage) {
Label label = new Label("Label");
label.setStyle("-fx-background-color: lightcyan");
VBox vBox = new VBox();
vBox.setStyle("-fx-background-color: #efecc2");
vBox.getChildren().add(label);
AnchorPane root = new AnchorPane();
root.getChildren().add(vBox);
Scene scene = new Scene(root, 500, 300);
primaryStage.setScene(scene);
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}