Label not showing on mouse event JavaFx

问题

I have a pie chart where i have added a mouse listener using this guide:

Oracle guide to pie chart

However when i run my program and click on the chart it doesnt do anything.

I have tried to System.out.println(caption.getText()); and the text of the label is correct however the label is just not showing up.

My code is as following:

public void start(Stage stage) {
        Scene scene = new Scene(new Group());
        stage.setTitle("Imported Fruits");
        stage.setWidth(500);
        stage.setHeight(500);

        ObservableList<PieChart.Data> pieChartData =
                FXCollections.observableArrayList(
                new PieChart.Data("Grapefruit", 13),
                new PieChart.Data("Oranges", 25),
                new PieChart.Data("Plums", 10),
                new PieChart.Data("Pears", 22),
                new PieChart.Data("Apples", 30));
        final PieChart chart = new PieChart(pieChartData);
        chart.setTitle("Imported Fruits");

        ((Group) scene.getRoot()).getChildren().add(chart);

        final Label caption = new Label("");
        caption.setTextFill(Color.DARKORANGE);
        caption.setStyle("-fx-font: 24 arial;");

        for (final PieChart.Data data : chart.getData()) {
            data.getNode().addEventHandler(MouseEvent.MOUSE_PRESSED,
                new EventHandler<MouseEvent>() {
                    @Override public void handle(MouseEvent e) {
                        caption.setTranslateX(e.getSceneX());
                        caption.setTranslateY(e.getSceneY());
                        caption.setText(String.valueOf(data.getPieValue()) + "%");
                        caption.setVisible(true);
                     }
                });
        }

        stage.setScene(scene);
        stage.show();
    }

}

Can anyone tell me what i did wrong?

回答1:

You forgot to add the label 'caption' to the list of children in your root node :-)

public void start(Stage stage) {
        Scene scene = new Scene(new Group());
        stage.setTitle("Imported Fruits");
        stage.setWidth(500);
        stage.setHeight(500);

        ObservableList<PieChart.Data> pieChartData =
                FXCollections.observableArrayList(
                new PieChart.Data("Grapefruit", 13),
                new PieChart.Data("Oranges", 25),
                new PieChart.Data("Plums", 10),
                new PieChart.Data("Pears", 22),
                new PieChart.Data("Apples", 30));
        final PieChart chart = new PieChart(pieChartData);
        chart.setTitle("Imported Fruits");
        final ObservableList<Node> children = ((Group) scene.getRoot()).getChildren();

        children.add(chart);

        final Label caption = new Label("");
        caption.setTextFill(Color.DARKORANGE);
        caption.setStyle("-fx-font: 24 arial;");
        children.add(caption);

        for (final PieChart.Data data : chart.getData()) {
            data.getNode().addEventHandler(MouseEvent.MOUSE_PRESSED,
                new EventHandler<MouseEvent>() {
                    @Override public void handle(MouseEvent e) {
                        caption.setTranslateX(e.getSceneX());
                        caption.setTranslateY(e.getSceneY());
                        caption.setText(String.valueOf(data.getPieValue()) + "%");
                        caption.setVisible(true);
                     }
                });
        }

        stage.setScene(scene);
        stage.show();
    }

I have made the above change and can verify that it works (as depicted by the image below)

回答2:

no need for that, you just have to add caption, here: Change this line :((Group) scene.getRoot()).getChildren().addAll(chart); to :((Group) scene.getRoot()).getChildren().addAll(chart,caption);

来源：https://stackoverflow.com/questions/13880356/label-not-showing-on-mouse-event-javafx