JFreeChart蜘蛛網圖添加刻度解決方案

JFreeChart是老牌Java開源圖表工具包，也是JFreeReport的重要組成部分，在業界被廣泛應用。當然，這個工具包依然有很多美中不足，确切的說，有很多具體的應用還需要我們拓展，比如蜘蛛網圖（Spider Web）的刻度問題。

這是使用原來SpiderWebPlot時解決前的圖示：

下面是使用MySpiderWebPlot解決後的圖示：

MySpiderWebPlot代碼如下：

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); 

                        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; 

                                        } 

                                } else { 

                                        if (labelY > plotArea.getCenterY()) { 

                                                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參考這個思路繼續擴充。

遇到問題，不抱怨社會，不在一棵樹上吊死。

本文轉自 王傑瑞 51CTO部落格，原文連結：http://blog.51cto.com/wangjierui/116845，如需轉載請自行聯系原作者