JFreeChart 实现全图tooptip
之前也没有接触过JFreeChart，如有错误或更简单的实现恳请指出， 谢谢。JFreeChart的默认只有鼠标在数据点上的时候才显示tooltip；两点之间的数据就不能显示tooptip，如果数据是滚动变化的就更难使用。 所以决定干脆鼠标放哪，就显示鼠标点的数据。
最终效果如下图：
http://dl.iteye.com/upload/attachment/164345/ad464b2e-6342-31e7-897c-6bc4c61d3817.png
查了下Api，JFreeChart好像没有这样的功能，只好自己实现了.
JFreeChart中画图的面板是ChartPanel, tooltip的文字内容也是由这个类产生的.只要继承ChartPanel并重载getToolTipText方法就行了。下面是代码实现：
package com.straw;public class ToolTipChartPanel extends ChartPanel{ private ValueAxis xAxis; private ValueAxis yAxis; private SimpleDateFormat sdf = new SimpleDateFormat("hh:mm:ss"); public ToolTipChartPanel(JFreeChart chart, XYPlot xyplot) { super(chart); this.xAxis = xyplot.getDomainAxis(); this.yAxis = xyplot.getRangeAxis(); } @Override public String getToolTipText(MouseEvent e) { Rectangle2D dataArea = getScaledDataArea(); // 不在区域内的直接返回 if (!dataArea.contains(e.getX(), e.getY() )) { return null; } long x = getValueX(dataArea, e.getX()); double y = getValueY(dataArea, e.getY()); return sdf.format(new Date(x)) + ", " + 100*y + "%"; } private long getValueX(Rectangle2D dataArea, int mouseX) { // 1 获得像素值 long x = (long) (mouseX - dataArea.getMinX()); // 2 转化成时间毫秒 double lowerBound = xAxis.getLowerBound(); double upperBound = xAxis.getUpperBound(); x = (long) (x*(upperBound - lowerBound)/dataArea.getWidth() + lowerBound); return x; } private double getValueY(Rectangle2D dataArea, int mouseY) { // 1 获得像素值 double y = (dataArea.getHeight() - (mouseY - dataArea.getMinY())); // 2 转化成数值 double lowerBound = yAxis.getLowerBound(); double upperBound = yAxis.getUpperBound(); y =(y*(upperBound - lowerBound)/dataArea.getHeight() + lowerBound); return y; }}
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