相对于原点的鼠标位置

Question

如何计算鼠标相对于折线图原点的位置？

下面的代码获取鼠标光标相对于图表布局原点的x位置。我想知道相对于笛卡尔原点的鼠标位置。

public class Chart extends Application { 

    private NumberAxis xAxis; 
    private NumberAxis yAxis; 
    private LineChart<Number,Number> lineChart; 
    private Label cursorPosition; 
    private Label xAxisPosition; 

    @Override 
    public void start(Stage primaryStage) { 
     VBox root = new VBox(); 

     xAxis = new NumberAxis("Date", 0.f, 100.f, 10.f); 
     yAxis = new NumberAxis("Value", 0.f, 100.f, 10.f); 
     lineChart = new LineChart<>(xAxis, yAxis); 

    Series series = new Series(); 
    for (int ii = 1; ii <= 100; ii++) { 
     series.getData().add(new Data(ii, Math.random()*20.)); 
    } 
    lineChart.getData().add(series); 

    lineChart.setOnMouseMoved(new EventHandler<MouseEvent>() { 
     @Override 
     public void handle(MouseEvent event) { 
      lineChart.setCursor(Cursor.CROSSHAIR); 
      cursorPosition.setText(String.valueOf(event.getX())); 
     } 
    }); 

    lineChart.setOnMouseExited(new EventHandler<MouseEvent>() { 
     @Override 
     public void handle(MouseEvent event) { 
      lineChart.setCursor(Cursor.DEFAULT); 
     } 
    }); 

    cursorPosition = new Label(); 
    root.getChildren().addAll(lineChart, cursorPosition,); 

    Scene scene = new Scene(root, 300, 250); 
    primaryStage.setScene(scene); 
    primaryStage.show(); 
} 

Answer 1

您必须使用图表的轴在显示坐标和笛卡尔坐标（值）之间进行转换。例如，xAxis.getDisplayPosition(0)会为您提供值为0的x坐标。您还可以使用它将当前鼠标位置转换为“值”。