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Oundroni
Asked: 2020-02-17 06:44:25 +0800 CST 2020-02-17 06:44:25 +0800 CST

Get the background color of a JavaFX control

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I want to read the background color of a control from javaFX code and then apply a transparency to it. I have been looking for information but I am not clear. There is no method getBackgroundColor()but if getBackground()although I'm lost, any idea?

javafx

2 Answers

  1. See if this is what you need in this link: window with shaded edges

    The part to watch carefully is:

    stage.initStyle(StageStyle.TRANSPARENT);

    Y

    // Establecer el color de relleno del Scene a transparente
scene.setFill(Color.TRANSPARENT);
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  2. Best Answer

    Sorry for the kilometric answer, I hadn't used JavaFX for a long time and for that reason I investigated a little more thoroughly.

    Short answer:

    You can get the colors used for the background from the method getBackground, which itself has a list of the colors used inside, and unless you're using a gradient or something similar, the first fill should be the unique background color of your object.

    Color color = (Color) boton.getBackground().getFills().get(0).getFill();
System.out.println("color:"+color);

    Long answer:

    It is important that you differentiate between the color that is set programmatically and the one that is set from the style , since the styles have a higher preference than the normal background colors and can produce subtle errors, which may or may not work in our favor and I always suggest using programmatic colors instead of javafx css styles.

    Let's see a simple example, if you have an fxml with a button like this:

    <Button fx:id="btnrojillo" layoutX="16.0" layoutY="128.0" mnemonicParsing="false" onAction="#handleSubmitButtonAction" style="-fx-background-color: blue;" text="Button" />

    and in your button handles you poes something like:

    @FXML
protected void handleSubmitButtonAction(ActionEvent event) {
    String style = btnrojillo.getStyle();

    System.out.println(style);
    btnrojillo.setStyle("-fx-background-color: red;");
    String colorDesdeEstilo = style.replaceAll(".*(-fx-background-color:\\s?([a-zA-Z0-9]+)).*", "$2");


    System.out.println("color detectado desde hoja de estilos:" +
            colorDesdeEstilo
    );

    Color color = (Color) btnrojillo.getBackground().getFills().get(0).getFill();
    System.out.println("color detectado desde configuración de componente:" + color.toString().substring(2));
}

    The first time you run it you will get a very horrible NPE (Not what you think naughty ;) ) like this:

    Caused by: java.lang.NullPointerException

    at swinginterop.Model.handleSubmitButtonAction

    Now if we add a color selector to our 

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ColorPicker?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane prefHeight="400.0" prefWidth="250.0" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="swinginterop.Model">
   <children>
      <AnchorPane layoutX="36.0" layoutY="47.0" prefHeight="266.0" prefWidth="258.0">
         <children>
            <ColorPicker fx:id="colorchooser" layoutX="11.0" layoutY="40.0" onAction="#handleColorSelectedAction" />
            <Button fx:id="btnrojillo" layoutX="16.0" layoutY="128.0" mnemonicParsing="false" onAction="#handleSubmitButtonAction" style="-fx-background-color: blue;" text="Button" />
         </children></AnchorPane>
   </children>
</AnchorPane>

    And in our Java code

    @FXML
protected void handleSubmitButtonAction(ActionEvent event) {
    String style = btnrojillo.getStyle();

    System.out.println(style);
    String colorDesdeEstilo = style.replaceAll(".*(-fx-background-color:\\s?([a-zA-Z0-9]+)).*", "$2");


    System.out.println("color detectado desde hoja de estilos:" +
            colorDesdeEstilo
    );

    Color color = (Color) btnrojillo.getBackground().getFills().get(0).getFill();
    System.out.println("color detectado desde configuración de componente:" + color.toString().substring(2));
}


@FXML
protected void handleColorSelectedAction(ActionEvent event) {
    String value = colorchooser.getValue().toString().substring(2);
    btnrojillo.setBackground(new Background(new BackgroundFill(
                    colorchooser.getValue(), null, null
            )
            )
    );

}

    We will notice that the color only changes temporarily and returns to the color defined in the style.

    That is why I recommend that if you need to modify the color, do it directly in the style property.

    FXML:

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ColorPicker?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane prefHeight="400.0" prefWidth="250.0" xmlns="http://javafx.com/javafx/8.0.172-ea" xmlns:fx="http://javafx.com/fxml/1" fx:controller="swinginterop.Model">
   <children>
      <AnchorPane layoutX="36.0" layoutY="47.0" prefHeight="266.0" prefWidth="258.0">
         <children>
            <ColorPicker fx:id="colorchooser" layoutX="11.0" layoutY="40.0" onAction="#handleColorSelectedAction" />
            <Button fx:id="btnrojillo" layoutX="16.0" layoutY="128.0" mnemonicParsing="false" onAction="#handleSubmitButtonAction" style="-fx-background-color: blue;" text="Button" />
         </children></AnchorPane>
   </children>
</AnchorPane>

    Java:

    package swinginterop;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ColorPicker;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.paint.Color;
import javafx.scene.paint.Paint;
import javafx.stage.Stage;

public class Model extends Application {
    @FXML
    private Button btnrojillo;

    @FXML
    ColorPicker colorchooser;

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FórmulasGrasa.fxml"));
        Scene scene = new Scene(root, 300, 275);

        stage.setTitle("FXML Welcome");
        stage.setScene(scene);
        stage.show();
    }

    @FXML
    protected void handleSubmitButtonAction(ActionEvent event) {
        String style = btnrojillo.getStyle();

        System.out.println(style);
        String colorDesdeEstilo = style.replaceAll(".*(-fx-background-color:\\s?([a-zA-Z0-9]+)).*", "$2");


        System.out.println("color detectado desde hoja de estilos:" +
                colorDesdeEstilo
        );

        Color color = (Color) btnrojillo.getBackground().getFills().get(0).getFill();
        System.out.println("color detectado desde configuración de componente:" + color.toString().substring(2));
    }

    @FXML
    protected void handleColorSelectedAction(ActionEvent event) {
        String value = colorchooser.getValue().toString().substring(2);
        Paint red = Paint.valueOf(value);
        btnrojillo.setBackground(new Background(new BackgroundFill(
                        colorchooser.getValue(), null, null
                )
                )
        );

        btnrojillo.setStyle("-fx-background-color: #"+value+';');

    }

    public static void main(String args[]) {
        launch(args);
    }
}

    If you happen to be doing color binding, I recommend you read this question in English .

    If you use transparency you can try in the css with something like:

    -fx-background-color: none;

    or if you are directly modifying the Background from code by setting the fills to null.

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