Tooltip on Live LineChart

Question

I found many examples how to add Tooltip on a LineChart but no information or example how to add Tooltip on Live LineChart.

import java.util.concurrent.Concu         


        

Answer 1

First, use a regular AreaChart instead of the anonymous subclass you are using (i.e. don't override the dataAddedItem(...) method). That method creates a default node to display for the data point if none already exists (this is a huge violation of separating data from presentation, imho, but there's nothing we can do about that...); you obviously need a graphic there to attach the tooltip to.

Once the data point has a node, you don't need to listen to the changes, so in your addDataToSeries() method, remove the listener and just replace it with

        Tooltip t = new Tooltip(data.getYValue().toString() + '\n' + data.getXValue());
        Tooltip.install(data.getNode(), t);

Or, just create your own graphic, attach a tooltip to it, and pass it to data.setNode(...);.

You will still have a general usability problem; I don't see how the user is going to hover over a data point in the chart when everything is flying by at 5 units per second. And even if they could, by the time the tooltip appeared the points would have moved, so the values would be incorrect...

Update:

Just for fun, I tried this:

    ObjectProperty mouseLocationInScene = new SimpleObjectProperty<>();

    Tooltip tooltip = new Tooltip();

    sc.addEventHandler(MouseEvent.MOUSE_MOVED, evt -> {
        if (! tooltip.isShowing()) {
            mouseLocationInScene.set(new Point2D(evt.getSceneX(), evt.getSceneY()));
        }
    });

    tooltip.textProperty().bind(Bindings.createStringBinding(() -> {
        if (mouseLocationInScene.isNull().get()) {
            return "" ;
        }
        double xInXAxis = xAxis.sceneToLocal(mouseLocationInScene.get()).getX() ;
        double x = xAxis.getValueForDisplay(xInXAxis).doubleValue();
        double yInYAxis = yAxis.sceneToLocal(mouseLocationInScene.get()).getY() ;
        double y = yAxis.getValueForDisplay(yInYAxis).doubleValue() ;
        return String.format("[%.3f, %.3f]", x, y);
    }, mouseLocationInScene, xAxis.lowerBoundProperty(), xAxis.upperBoundProperty(),
    yAxis.lowerBoundProperty(), yAxis.upperBoundProperty()));

    Tooltip.install(sc, tooltip);

This sets a tooltip on the chart that updates both as you move the mouse and as the chart scrolls below. This combines ideas from this question and this one.