JavaFX 如何使节点始终位于最前面并完全可见？

Question

此程序生成图表并在鼠标进入绘制点时显示坐标值，将点替换为标签。

但问题是如果点在图表的边框中，标签不会完全显示。

我无法使用 toFront() 和 toBack() 函数解决此问题。

我的代码改编自这个问题的答案 JavaFX LineChart Hover Values，它有同样的错误。

Chart.java

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;

public class Chart extends Application {

@Override
public void start(Stage stage) {

    // Random chart
    // Defining the Axis
    final NumberAxis xAxis = new NumberAxis();
    final NumberAxis yAxis = new NumberAxis();
    // Creating the chart
    LineChart<Number, Number> lineChart = new LineChart(xAxis, yAxis);

    // This didn't solve the bug
    xAxis.toBack();
    yAxis.toBack();

    // Preparing the series
    XYChart.Series series = new XYChart.Series();
    series.setName("Chart");

    for (double x = 0; x <= 10; x++) {
        double y = Math.random() * 100;
        XYChart.Data chartData;
        chartData = new XYChart.Data(x, y);
        chartData.setNode(new ShowCoordinatesNode(x, y));
        series.getData().add(chartData);
    }

    // Adding series to chart
    lineChart.getData().add(series);

    Scene scene = new Scene(lineChart, 800, 600);
    stage.setScene(scene);
    stage.show();
}

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

ShowCoordinatesNode.java

import java.text.DecimalFormat;
import javafx.event.EventHandler;
import javafx.scene.Cursor;
import javafx.scene.control.Label;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.StackPane;

public class ShowCoordinatesNode extends StackPane {

public ShowCoordinatesNode(double x, double y) {

    final Label label = createDataThresholdLabel(x, y);

    setOnMouseEntered(new EventHandler<MouseEvent>() {
        @Override
        public void handle(MouseEvent mouseEvent) {
                setScaleX(1);
                setScaleY(1);
                getChildren().setAll(label);
                setCursor(Cursor.NONE);
                toFront(); // This didn't solve the bug
        }
    });
    setOnMouseExited(new EventHandler<MouseEvent>() {
        @Override
        public void handle(MouseEvent mouseEvent) {
                getChildren().clear();
                setCursor(Cursor.CROSSHAIR);
        }
    });
}

private Label createDataThresholdLabel(double x, double y) {
    DecimalFormat df = new DecimalFormat("0.##");
    final Label label = new Label("(" + df.format(x) + "; " + df.format(y) + ")");
    label.getStyleClass().addAll("default-color0", "chart-line-symbol", "chart-series-line");
    label.setStyle("-fx-font-size: 10; -fx-font-weight: bold;");
    label.setMinSize(Label.USE_PREF_SIZE, Label.USE_PREF_SIZE);
    label.setId("show-coord-label");
    return label;
}
}

Answer 1

我进行了一些搜索，试图使这项工作正常进行，toFront 无法像 Javadoc 所述那样工作的原因

Moves this Node to the front of its sibling nodes in terms of z-order. This is accomplished by moving this Node to the last position in its parent's content ObservableList. This function has no effect if this Node is not part of a group.

所以我无法让它在任何意义上发挥作用。这是我能想到的唯一解决方案，它涉及找出 label/2 的 width/height 并移动标签（如果它在 X 或 Y 轴上）以便您可以看到它

除了硬编码测试值和删除 toFront 调用外，我在 Main 中没有做任何更改

public class Main extends Application {

    @Override
    public void start(Stage stage) throws Exception{
        // Random chart
        // Defining the Axis
        final NumberAxis xAxis = new NumberAxis();
        final NumberAxis yAxis = new NumberAxis();
        // Creating the chart
        LineChart<Number, Number> lineChart = new LineChart<>(xAxis, yAxis);

        // Preparing the series
        XYChart.Series series = new XYChart.Series();
        series.setName("Chart");

        boolean firstRun = true;//First point at 0,0 to test
        for (double x = 0; x <= 10; x++) {
            double y;
            if(firstRun) {
                y = 0.0;
                firstRun = false;
            }else
                y = Math.random() * 100;
            XYChart.Data chartData;
            chartData = new XYChart.Data<>(x, y);
            chartData.setNode(new ShowCoordinatesNode(x, y));
            series.getData().add(chartData);
        }

        // Adding series to chart
        lineChart.getData().add(series);

        Scene scene = new Scene(lineChart, 800, 600);
        stage.setScene(scene);
        stage.show();
    }

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

}

我在此处添加了 2 个 If 语句以在其中一个轴上翻译标签 if

public class ShowCoordinatesNode extends StackPane {


    public ShowCoordinatesNode(double x, double y) {

        final Label label = createDataThresholdLabel(x, y);

        setOnMouseEntered(mouseEvent -> {
            setScaleX(1);
            setScaleY(1);
            getChildren().setAll(label);

            if(x == 0.0) {
                applyCss();
                layout();
                label.setTranslateX(label.getWidth()/2);
            }
            if(y == 0.0){
                applyCss();
                layout();
                label.setTranslateY(-label.getHeight()/2);
            }

            setCursor(Cursor.NONE);
        });
        setOnMouseExited(mouseEvent -> {
            getChildren().clear();
            setCursor(Cursor.CROSSHAIR);
        });
    }

    private Label createDataThresholdLabel(double x, double y) {
        DecimalFormat df = new DecimalFormat("0.##");
        final Label label = new Label("(" + df.format(x) + "; " + df.format(y) + ")");
        label.getStyleClass().addAll("default-color0", "chart-line-symbol", "chart-series-line");
        label.setStyle("-fx-font-size: 10; -fx-font-weight: bold;");
        label.setMinSize(Label.USE_PREF_SIZE, Label.USE_PREF_SIZE);
        label.setId("show-coord-label");
        return label;
    }
}

我使用 applyCSS() 来计算标签的大小，然后再添加到 window JavaDoc 指出：

If required, apply styles to this Node and its children, if any. This method does not normally need to be invoked directly but may be used in conjunction with Parent.layout() to size a Node before the next pulse, or if the Scene is not in a Stage.

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