Here's what I had in mind about keeping support for
SXSSFSheet.autoSizeColumn(int) and autoSizeColumn(int, bool):
int rowAccessWindowSize = 1;
SXSSFWorkbook wb = new SXSSFWorkbook(rowAccessWindowSize);
SXSSFSheet sh = wb.createSheet();
AutosizeColumnTracker tracker = sh.getAutosizeColumnTracker(); //this
probably needs to be a singleton. Can be lazily-created.
// tell workbook to keep track of column widths as they *might* be
auto-sized at the end of the sheet
boolean useMergedCells = false;
tracker.monitorColumn(0, useMergedCells);
tracker.monitorColumn(2, useMergedCells);
tracker.monitorColumn(4); // equivalent to monitorColumn(4, true);
// create a bunch of rows and cells, write some values to the cells, merge
some cells across columns and rows so auto-size has something meaningful to
do
Row row;
Cell cell;
for (int r=0; r<=10; r++) {
row = sh.createRow(r);
for (int c=0; c<=10; c++) {
cell = row.createCell(0);
cell.setCellValue("row=" + r + ", column=" + c + ",
somethingToMakeColumnsHaveDifferentWidth=" + ((int) Math.pow(r, c)));
}
}
// ... etc
sh.autoSizeColumn(0); // okay
sh.autoSizeColumn(0, false); // okay
sh.autoSizeColumn(0, true); // throws exception: column widths were
calculated using merged cell widths, but this pre-requisite is no longer
valid.
sh.autoSizeColumn(1); // throws exception: column was not monitored for
auto-sizing
sh.autoSizeColumn(2); // okay
// and if we want to allow a user to auto-size a column that wasn't
previously monitored, we might need to add an extra method that will
indicate that the user understands that auto-sizing is computed solely from
the row access window, and not to throw an UnmonitoredColumnForAutosize
(insert your favorite name here) exception.
autoSizeRowAccessWindowOnly = true;
sh.autoSizeColumn(0, false, autoSizeRowAccessWindowOnly); // okay: makes
existing functionality available
// alternatively, if you want to allow the user to determine if a column
gets autosized using merged cells or not at the time autoSizeColumn is
called, the AutosizeColumnTracker would need to calculate and remember the
widths for both cases (useMergedCells=true and useMergedCell=false).
// finish up
// ... etc
wb.write(new FileOutputStream('example.xlsx'));
I think the relationship between the tracker object and the SXSSFSheet
warrants more discussion, as there are several ways to do this.
Considerations:
* extensibility: how can the AutosizeColumnTracker class be subclassed by
users of POI? how can the SXSSFSheet be subclassed by users of POI? Should
AutosizeColumnTracker be final or @Internal to avoid this question?
* reusability: is there a need to create one autosize column tracker object
that can be applied to multiple sheets (whether this is just the index of
the monitored columns or also the column widths)?
* if sh.autoSizeColumn uses the tracker, either the tracker needs to be
passed in as a third argument or the sheet needs to know what tracker it is
associated with. Every time a column goes outside the window, the
SXSSFSheet needs to know which tracker object its associated with so it can
update the column widths in the tracker (or maintain its own column
widths). In your code, you require the user to explicitly call trackRow,
but XSSFSheet and HSSFSheet don't have a similar construct: auto-sizing
applies to ALL rows and this is not user configurable.
* My vision of the AutosizeColumnTracker may be too tightly coupled with
the SXSSFSheet. At the tightly-coupled extreme, AutosizeColumnTracker may
be a private class (or just a private TreeMap member variable) inside of
SXSSFSheet that maintains a TreeMap of tracked columns and column widths;
all intents are registered directly on the SXSSFSheet:
sxssfSheet.monitorColumnForAutosizing(0);
Thoughts?
Javen
