Problem in extending DateAxis

[shehriih]

Hi all i am trying to extends DateAxis to cutomize draw method

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public class MyDateAxis extends DateAxis

and when creating JfreeChart

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JFreeChart jfreechart = ChartFactory.createGanttChart("Gantt Chart Demo", "Task", "Date", intervalcategorydataset, true, true, false);

CategoryPlot categoryplot = (CategoryPlot)jfreechart.getPlot();

MyDateAxis da = (MyDateAxis )categoryplot.getRangeAxis(); // causes ClassCastException 
// org.jfree.chart.axis.DateAxis cannot be cast to MyDateAxis 

please help on that !

[paradoxoff]

Hi,
I assume it is quite easy: since you can´t specify the type of the RangeAxis in the factory method, the factory has to guess the type of the range axis and is creating a NumberAxis by default. This, of course, can´t be cast to a DateAxis or any subclass of it! Instead of using the getter, simply use a setter:

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categoryplot.setRangeAxis(new (MyDateAxis))

That is one reason why I avoid the factory methods, because in that case you can never be sure what is really created.
Regards, paradoxoff

[shehriih]

sorry,

but it works if you cast it to DateAxis

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DateAxis da = (DateAxis)categoryplot.getRangeAxis(); 

[david.gilbert]

Of course it does, because it IS a DateAxis. But it will never be a MyDateAxis until you call setRangeAxis() and make it so.

[paradoxoff]

Yep, sorry, of course David is right. I should think better before I post.

[shehriih]

thanks all

of course , you can not assign DateAxis to MyDateAxis


i have just checked the code

sorry..