Java Fx - Adding Styles to label programattically without overwriting

I want to add styles to a label depending on conditions. When i try this, it overwrites the previous style. Is there a better way to concat the styles ?

    Label lbl = new Label(labelDescription.getLabelText());

    if (labelDescription.getLabelStyling() == LabelStyling.BOLD) {
        lbl.setStyle("-fx-font-weight: bold;");
    }

    if (labelDescription.getLabelStyling() == LabelStyling.ITALIC) {
        lbl.setStyle("-fx-font-style: italic;");
    }

    if (labelDescription.getTextSize() != null) {
        lbl.setStyle("-fx-font-size: " + labelDescription.getTextSize() + "px;");
    }

I think it could be easier for your case to refactor a little the styling logic, like this:

Label lbl = new Label(labelDescription.getLabelText());

String style = "";
if (labelDescription.getLabelStyling() == LabelStyling.BOLD) {
    style += "-fx-font-weight: bold;";
}

if (labelDescription.getLabelStyling() == LabelStyling.ITALIC) {
    style += "-fx-font-style: italic;";
}

if (labelDescription.getTextSize() != null) {
    style += "-fx-font-size: " + labelDescription.getTextSize() + "px;";
}

lbl.setStyle(style);

Although this could be pretty inefficient if more than these 3 values are set, you should consider using StringBuilder

Hope it helped!

Note you can just set the font programmatically, without using CSS at all:

Label lbl = new Label(labelDescription.getLabelText());
// get defaults:
Font font = lbl.getFont();
String family = font.getFamily();
double size = font.getSize();
FontPosture posture = FontPosture.REGULAR ;
FontWeight weight = FontWeight.NORMAL ;
if (labelDescription.getLabelStyling() == LabelStyling.BOLD) {
weight = FontWeight.BOLD ;
}
if (labelDescription.getLabelStyling() == LabelStyling.ITALIC) {
posture = FontPosture.ITALIC ;
}
if (labelDescription.getTextSize() != null) {
size = labelDescription.getTextSize();
}
lbl.setFont(Font.font(family, weight, posture, size));

If you really want to use CSS, you can either build the style via string concatenation, or for the font weight and style use an external style sheet and custom CSS pseudoclasses.

E.g.:

label-style.css:

<!-- language: lang-css -->

/*
Note that you have to use a font which supports
bold, italic, and bold-italic on the system.
*/
#my-label {
-fx-font-family: "Arial" ;
}
#my-label:important {
-fx-font-weight: bold ;
}
#my-label:emphasized {
-fx-font-style: italic ;
}

I generally prefer this approach, as it makes it easier to programmatically change styles in responses to changes in state in the application in a logical way. For colors you can use "looked-up colors". The only downside is that I know of no way to change font sizes, so those still need to be done via inline styles.

Here's a complete example using this, which sets the pseudoclasses according to user input:

import javafx.application.Application;
import javafx.css.PseudoClass;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.CheckBox;
import javafx.scene.control.Label;
import javafx.scene.control.Spinner;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
public class LabelStyleTest extends Application {
public static void main(String[] args) {
Application.launch(args);
}
@Override
public void start(Stage primaryStage) throws Exception {
VBox root = new VBox(5);
root.setAlignment(Pos.CENTER);
CheckBox important = new CheckBox("Important");
CheckBox emphasized = new CheckBox("Emphasized");
Spinner<Integer> size = new Spinner<>(4, 36, 12);
HBox sizeBox = new HBox(2, new Label("Size:"), size);
sizeBox.setAlignment(Pos.CENTER);
Label label = new Label("A label");
label.setId("my-label");
PseudoClass importantPC = PseudoClass.getPseudoClass("important");
PseudoClass emphasizedPC = PseudoClass.getPseudoClass("emphasized");
important.selectedProperty().addListener((obs, wasSelected, isNowSelected) -> 
label.pseudoClassStateChanged(importantPC, isNowSelected));
emphasized.selectedProperty().addListener((obs, wasSelected, isNowSelected) -> 
label.pseudoClassStateChanged(emphasizedPC, isNowSelected));
size.valueProperty().addListener((obs, oldSize, newSize) -> 
label.setStyle("-fx-font-size: "+newSize+" px;"));
root.getChildren().addAll(important, emphasized, sizeBox, label);
Scene scene = new Scene(root, 800, 500);
scene.getStylesheets().add("label-style.css");
primaryStage.setScene(scene);
primaryStage.show();
}
}

In your sample you would do something like:

Label lbl = new Label(labelDescription.getLabelText());
lbl.setId("my-label");
PseudoClass importantPC = PseudoClass.getPseudoClass("important");
PseudoClass emphasizedPC = PseudoClass.getPseudoClass("emphasized");
lbl.pseudoClassStateChanged(importantPC, 
labelDescription.getLabelStyling() == LabelStyling.BOLD));
lbl.pseudoClassStateChanged(emphasizedPC, 
labelDescription.getLabelStyling() == LabelStyling.ITALIC);
if (labelDescription.getTextSize() != null) {
lbl.setStyle("-fx-font-size: " + labelDescription.getTextSize() + "px;");
}