在工具提示代码中无限触发两个鼠标事件的奇怪行为

Question

I am trying to implement a custom tooltip using the javafx.stage.Popup . The sample demo code is:

public class PopupDemo extends Application {

    private Popup tooltip;
    private final SepiaTone sepiaTone = new SepiaTone();

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

    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("PopupDemo");

        Label content = new Label();
        content.setStyle("-fx-background-color:#FCFBBD; -fx-padding: 5; -fx-border-color: #BFBD3B");

        tooltip = new Popup();
        tooltip.getContent().add(content);

        VBox vbox = new VBox(10);
        for (int i = 0; i < 5; i++) {
            final Label lbl = new Label("item " + i);
            lbl.setStyle("-fx-border-color:darkgray; -fx-background-color:lightgray");
            lbl.setMaxSize(80, 60);
            lbl.setMinSize(80, 60);
            lbl.setAlignment(Pos.CENTER);

            lbl.setOnMouseEntered(new EventHandler<MouseEvent>() {

                @Override
                public void handle(final MouseEvent e) {
                    lbl.setEffect(sepiaTone);
                    lbl.setStyle("-fx-cursor: hand");
                    Label content = (Label) tooltip.getContent().get(0);
                    content.setText(lbl.getText());
                    tooltip.show(lbl, e.getScreenX(), e.getScreenY());
                }
            });
            lbl.setOnMouseExited(new EventHandler<MouseEvent>() {

                @Override
                public void handle(MouseEvent e) {
                    lbl.setEffect(null);
                    lbl.setStyle("-fx-cursor: default");
                    tooltip.hide();
                }
            });

            vbox.getChildren().add(lbl);
        }

        StackPane root = new StackPane();
        root.setPadding(new Insets(20));
        root.getChildren().add(vbox);
        primaryStage.setScene(new Scene(root, 600, 400));
        primaryStage.show();
    }
}

When I move the mouse over the labels the popup shows up and it is working great. But in some cases the two mouse event handlers OnMouseEntered and OnMouseExited are being called continuously one after another. One can reproduce this by running provided example, maximising a window and hovering labels continuously.

Is there a way to avoid this? I'm using JavaFX 2.0.1. Thanks.

Answer 1

It's a classic problem: you put mouse at a point, node receives MouseEntered — tooltip appears under the mouse and covers the node triggering MouseExited .

To avoid that you can change tooltip.show(lbl, e.getScreenX(), e.getScreenY()) call to

tooltip.show(lbl, e.getScreenX() + 1, e.getScreenY() + 1);

Answer 2

This is not really an answer, so much as pointers to things you might try or investigate further.

You could look at the implementation of Tooltip Skin and Behavior to see how it handles some of these cases.

The easiest way to implement a custom popup is just to use a Tooltip, style it the way you need using css and use the Tooltip's setGraphic method to add any custom Node content you want.

If you prefer to use your own implementation, I think you need to keep track of whether the popup has been displayed or not, so you don't try to show it if it is already showing, etc. You may also need invoke the hiding of the popup by having a mouse exit handler installed on the popup itself. You also might want a click to dismiss function for the popup by implementing a mouse click handler on the popup. You should also consider whether you should do a straight subclass of Popup or PopupControl , though using Popup as you have is likely more straightforward.