JFreeChart蜘蛛网图添加刻度解决方案

JFreeChart是老牌Java开源图表工具包，也是JFreeReport的重要组成部分，在业界被广泛应用。当然，这个工具包依然有很多美中不足，确切的说，有很多具体的应用还需要我们拓展，比如蜘蛛网图（Spider Web）的刻度问题。

这是使用原来SpiderWebPlot时解决前的图示：

 

下面是使用MySpiderWebPlot解决后的图示：

MySpiderWebPlot代码如下：

public class MySpiderWebPlot extends SpiderWebPlot {
         private int ticks = DEFAULT_TICKS;
         private static final int DEFAULT_TICKS = 5;
         private NumberFormat format = NumberFormat.getInstance();
         private static final double PERPENDICULAR = 90;
         private static final double TICK_SCALE = 0.015;
         private int valueLabelGap = DEFAULT_GAP;
         private static final int DEFAULT_GAP = 10;
         private static final double THRESHOLD = 15;

        MySpiderWebPlot(CategoryDataset createCategoryDataset) {
                 super(createCategoryDataset);
        }

        @Override
         protected void drawLabel( final Graphics2D g2, final Rectangle2D plotArea, final double value,
                         final int cat, final double startAngle, final double extent) {
                 super.drawLabel(g2, plotArea, value, cat, startAngle, extent);
                 final FontRenderContext frc = g2.getFontRenderContext();
                 final double[] transformed = new double[2];
                 final double[] transformer = new double[2];
                 final Arc2D arc1 = new Arc2D.Double(plotArea, startAngle, 0, Arc2D.OPEN);

                 for ( int i = 1; i <= ticks; i++) {

                         final Point2D point1 = arc1.getEndPoint();

                         final double deltaX = plotArea.getCenterX();
                         final double deltaY = plotArea.getCenterY();
                         double labelX = point1.getX() - deltaX;
                         double labelY = point1.getY() - deltaY;

                         final double scale = (( double) i / ( double) ticks);
                         final AffineTransform tx = AffineTransform.getScaleInstance(scale, scale);
                         final AffineTransform pointTrans = AffineTransform.getScaleInstance(scale + TICK_SCALE, scale + TICK_SCALE);
                        transformer[0] = labelX;
                        transformer[1] = labelY;
                        pointTrans.transform(transformer, 0, transformed, 0, 1);
                         final double pointX = transformed[0] + deltaX;
                         final double pointY = transformed[1] + deltaY;
                        tx.transform(transformer, 0, transformed, 0, 1);
                        labelX = transformed[0] + deltaX;
                        labelY = transformed[1] + deltaY;



                         double rotated = (PERPENDICULAR);

                        AffineTransform rotateTrans = AffineTransform.getRotateInstance(Math.toRadians(rotated), labelX, labelY);
                        transformer[0] = pointX;
                        transformer[1] = pointY;
                        rotateTrans.transform(transformer, 0, transformed, 0, 1);
                         final double x1 = transformed[0];
                         final double y1 = transformed[1];

                        rotated = (-PERPENDICULAR);
                        rotateTrans = AffineTransform.getRotateInstance(Math.toRadians(rotated), labelX, labelY);

                        rotateTrans.transform(transformer, 0, transformed, 0, 1);

                         final Composite saveComposite = g2.getComposite();
                        g2.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER, 1.0f));

                        g2.draw( new Line2D.Double(transformed[0], transformed[1], x1, y1));

                         if (startAngle == this.getStartAngle()) {
                                 final String label = format.format((( double) i / ( double) ticks) * this.getMaxValue());
                                 final Rectangle2D labelBounds = getLabelFont().getStringBounds(label, frc);


                                 final LineMetrics lm = getLabelFont().getLineMetrics(label, frc);
                                 final double ascent = lm.getAscent();
                                 if (Math.abs(labelX - plotArea.getCenterX()) < THRESHOLD) {
                                        labelX += valueLabelGap;
                                        labelY += ascent / ( float) 2;
                                } else if (Math.abs(labelY - plotArea.getCenterY()) < THRESHOLD) {
                                        labelY += valueLabelGap;
                                } else if (labelX >= plotArea.getCenterX()) {
                                         if (labelY < plotArea.getCenterY()) {
                                                labelX += valueLabelGap;
                                                labelY += valueLabelGap;
                                        } else {
                                                labelX -= valueLabelGap;
                                                labelY += valueLabelGap;
                                        }
                                } else {
                                         if (labelY > plotArea.getCenterY()) {
                                                labelX -= valueLabelGap;
                                                labelY -= valueLabelGap;
                                        } else {
                                                labelX += valueLabelGap;
                                                labelY -= valueLabelGap;
                                        }
                                }
                                g2.setPaint(getLabelPaint());
                                g2.setFont(getLabelFont());
                                g2.drawString(label, ( float) labelX, ( float) labelY);
                        }
                        g2.setComposite(saveComposite);
                }
        }
}

有其它需要的朋友可以参考这个思路继续扩展。

遇到问题，不抱怨社会，不在一棵树上吊死。