JavaFX - Style first and last tab only - javafx

Question

Is there a way (CSS or Java) to style first and last tab only in a dynamic TabPane?
Example :
Thanks!

Answer 1

You can observe the ObservableList<Tab> returned by TabPane#getTabs() and update the style class of each Tab as appropriate. For example:
App.java:
import javafx.application.Application;
import javafx.collections.ListChangeListener.Change;
import javafx.collections.ObservableList;
import javafx.css.Styleable;
import javafx.scene.Scene;
import javafx.scene.control.Label;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;
import javafx.scene.control.TabPane.TabClosingPolicy;
import javafx.scene.control.TabPane.TabDragPolicy;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
public class App extends Application {
#Override
public void start(Stage primaryStage) {
TabPane pane = new TabPane();
pane.setTabClosingPolicy(TabClosingPolicy.ALL_TABS);
pane.setTabDragPolicy(TabDragPolicy.REORDER); // requires JavaFX 10+
pane.getTabs().addListener(App::tabsChanged);
pane.getTabs() // add tabs **after** adding ListChangeListener
.addAll(
new Tab("Test Tab #1", new StackPane(new Label("Content #1"))),
new Tab("Test Tab #2", new StackPane(new Label("Content #2"))),
new Tab("Test Tab #3", new StackPane(new Label("Content #3"))),
new Tab("Test Tab #4", new StackPane(new Label("Content #4"))),
new Tab("Test Tab #5", new StackPane(new Label("Content #5"))));
Scene scene = new Scene(pane, 600, 400);
scene.getStylesheets().add(getClass().getResource("/App.css").toExternalForm());
primaryStage.setScene(scene);
primaryStage.show();
}
private static void tabsChanged(Change<? extends Tab> c) {
while (c.next()) {
if (c.wasRemoved()) {
for (Tab removed : c.getRemoved()) {
removed.getStyleClass().removeAll("first-tab", "last-tab");
}
}
}
ObservableList<? extends Tab> tabs = c.getList();
if (tabs.size() == 1) {
Tab tab = tabs.get(0);
addStyleClassIfAbsent(tab, "first-tab");
addStyleClassIfAbsent(tab, "last-tab");
} else if (!tabs.isEmpty()) {
Tab first = tabs.get(0);
addStyleClassIfAbsent(first, "first-tab");
first.getStyleClass().remove("last-tab");
Tab last = tabs.get(tabs.size() - 1);
addStyleClassIfAbsent(last, "last-tab");
last.getStyleClass().remove("first-tab");
for (Tab middle : tabs.subList(1, tabs.size() - 1)) {
middle.getStyleClass().removeAll("first-tab", "last-tab");
}
}
}
private static void addStyleClassIfAbsent(Styleable styleable, String styleClass) {
ObservableList<String> styleClasses = styleable.getStyleClass();
if (!styleClasses.contains(styleClass)) {
styleClasses.add(styleClass);
}
}
}
App.css:
.first-tab,
.last-tab {
-fx-base: pink;
}
The -fx-base is a looked-up color added by modena.css (i.e. the default user-agent stylesheet in JavaFX 8+). I set that instead of the -fx-background-color property in order to hook into the "theming" provided by modena.css. In the above example you can see the styles change dynamically by reordering the tabs via mouse-dragging (JavaFX 10+) or by closing tabs.
Note I would have preferred to use PseudoClass for this. However, from what I can tell, the Tab class does not allow you to (de)activate pseudo-classes directly. The way it handles the :selected pseudo-class is internal to the TabPane's default skin, meaning we can't access that same functionality reliably for our purposes from the outside.