On Jul 1, 2009, at 00:26, Peter Zegelin wrote:
I need to draw the background of a single row in a tableview. This
row is not the selected row, and it changes often. I have more or
less got it working but it seems like a bit of a hack so I'm
wondering if there is a better way. I've also checked various
examples but most want to draw the selected rows differently, not an
arbitrary row.
At the moment I subclass the cell for each of the columns of the
view ( same subclass). In my delegates objectValueForTableColumn I
set a variable 'shouldDrawRow' to true if that is the 'special' row
I want to draw myself.
In the cell subclass I override drawInteriorWithFrame and check to
see if this value is set in my delegate and if so call a delegate
method to draw the background first.
This seems like a real hack as it assumes that drawInteriorWithFrame
will be called straight after objectValueForTableColumn. This is
sort of reasonable because the cell is reused all the time so it
'works'. The other problem though is I want to draw the ends of the
rows differently to the middle ( thin rounded rectangle ) and
drawInteriorWithFrame only gives me the rectangle to draw in. I've
got no way of finding out which column it is. Again it will work
because the columns won't change so I can hard code some values.
However I'm thinking there must be a better way. What I really need
is some way of finding out the column and row of the cell about to
be drawn, but I can't see it. Am I missing something?
Such questions are hard to answer intelligently, because too much
depends on the details of your implementation, but that's never
stopped me from answering unintelligently before ...
I think it is a hack, and what you *really need* is to use your actual
data model.
That is, the objectValue for the columns in your special row need to
be recognizable as something different from the object values in the
non-special rows. Then your custom cell subclass, you test to see
whether its current objectValue is special, and draw it specially if
so. No fuss, no hacks, no hard-coded column assumptions.
For example, if the regular object values were NSNumber objects, and
the special row values were column totals, I'd wrap the NSNumber
totals inside a custom object and put those in the data model instead.
If that would mess up your data model for other purposes, I'd have
objectValueForTableColumn detect the special row index and return the
wrapped NSNumber when the row index dictates.
FWIW.
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