How to increment variable to count headlines, titles? - variables

Question

I have a JasperReports template, where I need to count the headlines of different "detail bands".
Now, since the headlines can vary (some datasets can be empty and then the whole band is not rendered), I wanted to use a variable for that.
The build-in variables does not suite, since they don't have a "detail_band_count" or something.
Moreover there is not always a headline in one detail band, there can be 1 or 10 following detail bands, where band 2 - 10 shares the same headline declared in band 1.
However, I managed to create a variable in this manner; but it only counts the pages.
Is there a possibility to call the Variable Expression on Variable access? So it would always increment, as soon as I write $V{headline_COUNT}?

Answer 1

It's hard for me to see how you can use variables, you would probably need to restructure report, find a grouping strategy, since you need to set incrementType to one of the available values and you are correct you can't select "header line" or similar.
However, there is a workaround that you can use to count how many time a specific element is showed using the parameter map $P{REPORT_PARAMETERS_MAP}
Define your counting parameter with a default value (avoid it starting as null)
<parameter name="countReportElement" class="java.lang.Integer" isForPrompting="false">
<defaultValueExpression><![CDATA[0]]></defaultValueExpression>
</parameter>
Now on any text field or other element in the band you like to count, you can use a fake printWhenExpression, to increment this parameter
<reportElement x="0" y="262" width="320" height="25" uuid="8fa62997-ffa2-4777-923b-999d372ce09e">
<printWhenExpression><![CDATA[($P{REPORT_PARAMETERS_MAP}.put("countReportElement",((Integer)$P{REPORT_PARAMETERS_MAP}.get("countReportElement"))+1))!=null?true:false]]></printWhenExpression>
</reportElement>
Note the ternary operation will always evaluate true (since Map.put(K key, V value) will return previous object) and put into the parameter map the value incremented by one every time element is evaluated.
To display the value of your count you access the parameter map directly.
<textField>
<reportElement x="57" y="13" width="100" height="20" uuid="7ca30577-0ca9-47c2-91ae-c7002fbbfbf7"/>
<textFieldExpression><![CDATA[$P{REPORT_PARAMETERS_MAP}.get("countReportElement")]]></textFieldExpression>
</textField>
be sure to set evaluationTime as need in report.