Adding Pre-Selected Z-Axis Values to the Simple Scatter Graph
This morning I read an email from a developer asking me if it would be possible to extend the functionality of the pseudo z-axis on the BKSimpleScatterGraph to allow for the pre-selection of certain values so that if these values were on an applet tag, then only those values would be selected on the initial view of the graph. After that, the graph would function normally, allowing them to show more, or less, as they wished.
The key to this was to be able to easily encode a list (Vector) of objects on a single applet PARAM tag. Since I'd already done something like this for the CKit Variant list, it seemed reasonable to extend it and then make it easy for the user to generate the encoded value and easy for me to decode it.
The format for the encoding of the list is pretty simple:
;value_1;value_2;...;value_n;
where each of the value_i is an encoded value itself. This allows for lists of lists and list of tables, etc. For this particular instance, it's going to be z-axis values, specifically, String values, and the encoding for a string is simply: S:value. So the encoded list of some strings looks like:
;S:one;S:two;S:three;
would be the Java Vector with string values 'one', 'two', and 'three' in it. Simple.
But I wanted to make it even easier for the developers. So easy that they don't have to know the encoding scheme. That's where the refactoring work on the BKTable comes into play. With this, it's as easy as saying:
Vector v = new Vector(); v.add("one"); v.add("two"); v.add("three"); String encoded = BKTable.generateCodeFromValues(v);
and then put encoded as the VALUE part of the PARAM tag. The NAME is going to be 'zvisible' and we're off to the races! On the applet side of things a simple call:
Vector v = BKTable.parseVectorFromCode(code);
gets me the Vector back from the code previously generated. Not bad at all.
When I put all this into the code, there were just a few little loose ends to clean up. Where would this list be read, and how would it default the graph? It took me an hour or so to wire it all up, but the hard part of refactoring the BKTable's encoding and decoding was done and it was pretty fast work after that. In the end, we have a wonderful way to pre-select the z-axis values on a SimpleScatterGraph. Not bad.
