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Calculated data on group footer

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By: yan orel - yanorel

Calculated data on group footer

2002-07-01 07:18

I have to put a custom calculated image on a group footer.

I didn't find the right event to handle the computing of the image.

I continue getting a java.lang.NullPointerException

at java.awt.Toolkit.createImage(Toolkit.java:705)


This is a part of xml:

<variable name="ImageVar" class="java.awt.Image" calculation="System"></variable>


--- This in the group footer (the only)

<image scaleImage="Clip" evaluationTime="Group" evaluationGroup="HourGroup"><reportElement x="190" y="3" width="300" height="5"/><graphicElement/> <imageExpression class="java.awt.Image"><![CDATA[$V{ImageVar}]]></imageExpression></image>







By: Teodor Danciu - teodord

RE: Calculated data on group footer

2002-07-04 08:38




Unfortunately, there is no event handler for group,

column or page footers in scriptlets.

In fact, what happens is that footers are always

printed before headers, so they don't have an event

for themselves. There are event callbacks only

when groups, columns or pages start.


I'll study this issues more thoroughly,

but is not a simple problem.


You have to treat every row in the data source like

it would be the last on the page, on the group,

or whatever.

This would imply that you recalculate your image

with every new detail hoping that the group end will

be reached and thus the current image used

on the group footer.

I know this will pose performance problems,

but the only thing I can promise is that I'll look

into this to come up with a better solution.


Thank you,





By: yan orel - yanorel

RE: Calculated data on group footer

2002-07-05 04:06

Thank you for the reply.


I solved my problem handling the groups in a better way working with the group footers.

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