问JavaFX TitledPane更改的标题背景在鼠标输入时重置

EN

import javafx.application.Application;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.TitledPane;
import javafx.scene.control.ToggleButton;
import javafx.scene.layout.Background;
import javafx.scene.layout.BackgroundFill;
import javafx.scene.layout.Region;
import javafx.scene.layout.StackPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class TitledPaneApplication extends Application {

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

    @Override
    public void start(Stage primaryStage) throws Exception {
        final StackPane root = new StackPane();

        final TitledPane titledPane = new TitledPane();
        titledPane.setText("Title");
        root.getChildren().add(titledPane);

        final String titleBackgroundValue = "#00ff11";
        final ToggleButton button = new ToggleButton("Change");
        button.setOnAction(event -> {
            boolean selected = button.isSelected();

            final Node node = titledPane.lookup(".title");
            if (selected) {
                final Color color = Color.valueOf(titleBackgroundValue);
                ((Region) node).setBackground(new Background(new BackgroundFill(color, null, null)));
            } else {
                ((Region) node).setBackground(null);
                titledPane.applyCss();
            }
        });

        button.setSelected(false);
        titledPane.setContent(button);

        final Scene scene = new Scene(root, 400, 400);
        scene.getStylesheets().add(getClass().getResource("light.css").toExternalForm());
        primaryStage.setScene(scene);
        primaryStage.setTitle("TestApplication");
        primaryStage.show();
    }

}

.root {
    -fx-base: rgb(240, 240, 240);
    -fx-background: rgb(240, 240, 240);
    -fx-border-color: rgb(220, 220, 220);

    /* make controls (buttons, thumb, etc.) slightly lighter */
    -fx-color: derive(-fx-base, 10%);

    /* text fields and table rows background */
    -fx-control-inner-background: rgb(248, 248, 248);
    /* version of -fx-control-inner-background for alternative rows */
    -fx-control-inner-background-alt: derive(-fx-control-inner-background, -2.5%);

    /* text colors depending on background's brightness */
    -fx-light-text-color: rgb(220, 220, 220);
    -fx-mid-text-color: rgb(100, 100, 100);
    -fx-dark-text-color: rgb(20, 20, 20);

    /* A bright blue for highlighting/accenting objects.  For example: selected
     * text; selected items in menus, lists, trees, and tables; progress bars */
    -fx-accent: rgb(0, 80, 100);

    /* color of non-focused yet selected elements */
    -fx-selection-bar-non-focused: rgb(50, 50, 50);

    -fx-font-family: "Roboto"; /* "Segoe UI Semibold", "Roboto", "Monospaced" */
    -fx-font-size: 1em;

    -primary-border-color: rgb(220, 220, 220);
}

/* Fix derived prompt color for text fields */
.text-input {
    -fx-prompt-text-fill: derive(-fx-control-inner-background, -50%);
}

/* Keep prompt invisible when focused (above color fix overrides it) */
.text-input:focused {
    -fx-prompt-text-fill: transparent;
}

/* Fix scroll bar buttons arrows colors */
.scroll-bar > .increment-button > .increment-arrow,
.scroll-bar > .decrement-button > .decrement-arrow {
    -fx-background-color: -fx-mark-highlight-color, rgb(220, 220, 220);
}

.scroll-bar > .increment-button:hover > .increment-arrow,
.scroll-bar > .decrement-button:hover > .decrement-arrow {
    -fx-background-color: -fx-mark-highlight-color, rgb(240, 240, 240);
}

.scroll-bar > .increment-button:pressed > .increment-arrow,
.scroll-bar > .decrement-button:pressed > .decrement-arrow {
    -fx-background-color: -fx-mark-highlight-color, rgb(255, 255, 255);
}

.text-field {
    -fx-font-size: 10pt;
}

.combo-box {
    -fx-font-size: 10pt;
}

/* ScrollPane style. */
.scroll-pane {
    -fx-background-color: transparent;
}

.scroll-pane > .viewport {
    -fx-background-color: transparent;
}

/* TabPane style. */
.tab-pane > .tab-header-area {
    -fx-background-color: transparent;
}

/* TitledPane style. */
.titled-pane {
    -fx-border-width: 1;
    -fx-border-color: -primary-border-color;
    -fx-effect: dropshadow(three-pass-box, rgba(0,0,0,0.15), 5, 0.0, 0, 1);
}

.titled-pane > .content {
    -fx-border-width: 0;
}

.titled-pane .title .arrow-button {
    visibility: false;
}

.titled-pane > .title {
    -fx-background-color: -primary-border-color;
    -fx-background-insets: 0;
    -fx-background-radius: 0 0 0 0;
    -fx-padding: 0.2em 0.2em 0.2em 0.2em;
}

.titled-pane > .title .text {
    -fx-font-size: 10pt;
}