如何在 Java FX 中以相对单位设置类别差距？

Question

假设我想在条形之间设置一个与条形大小相同的间隙。如果单位是百分比，我会设置100。但这不起作用：

public class StackedBarChart_Horizontal_Try extends Application {

    final static String itemA = "A";
    final static String itemB = "B";
    final static String itemC = "C";
    @Override
    public void start(Stage stage) {
        final NumberAxis xAxis = new NumberAxis();
        final CategoryAxis yAxis = new CategoryAxis();

        final StackedBarChart<Number, String> bc = new StackedBarChart<Number, String>(xAxis, yAxis);

        //bc.setBarGap(0);
        bc.setCategoryGap(100);




        bc.setTitle("Summary");
        xAxis.setLabel("Value");
        xAxis.setTickLabelRotation(90);
        yAxis.setLabel("Item");

        XYChart.Series series1 = new XYChart.Series();
        series1.setName("2003");
        series1.getData().add(new XYChart.Data(2, itemA));


        XYChart.Series series2 = new XYChart.Series();
        series2.setName("2004");
        series2.getData().add(new XYChart.Data(41, itemB));

        XYChart.Series series3 = new XYChart.Series();
        series3.setName("2005");
        series3.getData().add(new XYChart.Data(18, itemC));

        Scene scene = new Scene(bc, 800, 600);
        bc.getData().addAll(series1, series2, series3);
        stage.setScene(scene);
        stage.show();
    }

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

给予

并且在窗口调整大小时间隙的大小保持不变：

这意味着间隙以屏幕像素为单位设置。

如何设置轴单元大小的差距？

Answer 1

条形图的布局与您在此处要实现的目标相反：给定绘图区域的高度，布局机制首先为间隙分配空间，然后计算条形的大小基于剩余可用空间。

因此，执行此操作的方法是将categoryGapProperty 绑定到给定条数和绘图区域高度（与 y 轴高度相同）的正确大小。要为间隙和条分配相同数量的空间，您需要将间隙等于总高度除以条数的两倍：

bc.categoryGapProperty().bind(Bindings.createDoubleBinding(() ->
    yAxis.getHeight() / (2 * bc.getData().size()), 
    Bindings.size(bc.getData()), yAxis.heightProperty()));

完整示例：

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.scene.Scene;
import javafx.scene.chart.CategoryAxis;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.StackedBarChart;
import javafx.scene.chart.XYChart;
import javafx.stage.Stage;

public class StackedBarChart_Horizontal_Try extends Application {

    final static String itemA = "A";
    final static String itemB = "B";
    final static String itemC = "C";
    @Override
    public void start(Stage stage) {
        final NumberAxis xAxis = new NumberAxis();
        final CategoryAxis yAxis = new CategoryAxis();

        final StackedBarChart<Number, String> bc = new StackedBarChart<Number, String>(xAxis, yAxis);

        //bc.setBarGap(0);
//        bc.setCategoryGap(100);

        bc.categoryGapProperty().bind(Bindings.createDoubleBinding(() ->
            yAxis.getHeight() / (2 * bc.getData().size()), 
            Bindings.size(bc.getData()), yAxis.heightProperty()));


        bc.setTitle("Summary");
        xAxis.setLabel("Value");
        xAxis.setTickLabelRotation(90);
        yAxis.setLabel("Item");

        XYChart.Series series1 = new XYChart.Series();
        series1.setName("2003");
        series1.getData().add(new XYChart.Data(2, itemA));


        XYChart.Series series2 = new XYChart.Series();
        series2.setName("2004");
        series2.getData().add(new XYChart.Data(41, itemB));

        XYChart.Series series3 = new XYChart.Series();
        series3.setName("2005");
        series3.getData().add(new XYChart.Data(18, itemC));

        Scene scene = new Scene(bc, 800, 600);
        bc.getData().addAll(series1, series2, series3);
        stage.setScene(scene);
        stage.show();
    }

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

在不同的窗口大小下呈现：