Hi,
OK, I have been struggling along on this now for 3 days… time to get
an example from DevExpress to show me how this should really be done…
Here is what I am attempting to do: I want to have an unbound checkbox
column be the "surrogate" to populate a date field. When checked,
today's date goes into the date column. when unchecked, the date is cleared.
This seems pretty straight forward right? It aught to be!
Here is the code that handles drawing the checkbox column:
procedure TfmDesignDB.viewDataSelectCheckBoxCustomDrawCell(Sender:
TcxCustomGridTableView; ACanvas: TcxCanvas; AViewInfo:
TcxGridTableDataCellViewInfo; var ADone: Boolean);
var v : variant;
begin
v := AViewInfo.GridRecord.Values[viewDataDefPublishDate.Index];
if VarIsNull(v) or (v = false) then
TcxCustomCheckBoxViewInfo(AViewInfo.EditViewInfo).State := cbsUnChecked
else
TcxCustomCheckBoxViewInfo(AViewInfo.EditViewInfo).State := cbsChecked;
end;
This code seems to work correctly, and handles null correctly.
Here is the code that is triggered when the user clicks on the checkbox
column:
procedure
TfmDesignDB.cxEditRepositoryDataDefSelectCheckBoxPropertiesEditValueChanged(
Sender:
TObject);
var bChecked : boolean;
iRecordIndex : integer;
focusedRecord : TcxCustomGridRecord;
begin
bChecked := TcxCheckBox(sender).EditingValue;
iRecordIndex := viewDataDef.DataController.FocusedRecordIndex;
focusedRecord :=
viewDataDef.ViewData.GetRecordByRecordIndex(iRecordIndex);
SelectedRowChange(focusedRecord, viewDataSelectCheckBox.Index, bChecked);
end;
SelectedRowchange changes the date column, and that also works correctly.
The problem happens when the user clicks on the checkbox column for a
record where there is already a date and the dataController cache has
just been loaded or reloaded via UpdateItems. In this case the
OnDrawCell code is working correctly and painting a checked checkbox.
But the underlying dataController (I am guessing) the checkbox column is
null. So on the first click, it must be looking back to the
dataController to know what the new value should be. Since it is null,
it returns true. It was already true! It should now be false.
Hmmm, wonder if that made sense… hope so. The bottom line is -
regardless if the column is drawn as checked or not, upon initial load
of the dataController, the value will *always* be null since the
checkbox column is not data-bound. So the first click will always
produce a "true" result even if it is already drawn as checked. So to
make it false, the user actually has to click it twice. The first to go
from null to true. then a second click to go from true to false.
So, can DevExpress please provide an example of an unbound checkbox
column that acts as a surrogate to control a date column? Seems to me,
the "fix" for this would be that I assign values to the DataController's
checkbox column when it loads its cache. But that in itself seems to
have other side effects. Is that even possible?
frustratingly your,
-randall
Ticket
Q34130
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Hi randall,
Please review the attached sample and inform me whether it meets your requirements.
Thanks,
Dimitros
Well, your example works. but if you turn SmartRefresh off, which it has to be in our grid (cannot recall why, but there was a reason) then it fails. I tried wrapping the calls to TcxCustomRow.values within a datacontroller.begin/endUpdate but that does not help since EndUpdate eventually calls TcxCustomDataController.Update which (I think) then re-pulls in the data and all the check-box columns revert to unchecked again.
I also cannot use Datacontroller.SetEditValue since that operates against the EditingRecordIndex. I could hack TcxCustomDataProvider and call its SetEditValue, but that seems to be a wrapper around the dataController.SetValue which brings us right back to where we started.
So, would you like to have another crack at it? :)
-rs
Hi rs,
Sorry, but it's impossible to use an unbound column in a data-aware View when the SmartRefresh option is disabled. This is how the DataController works.
Thanks,
Dimitros
Well, if ya tell me it cannot be done, then I'll accept that. But keep in mind, this isn't really a completely unbound checkbox column. It is simply based on a date field. I think a better approach on this problem is to tweak the code that is forcing us to have SmartRefresh turned off.
thanx
rs
Hi rs,
I discussed this problem with our developers and we came to the decision that the current DataController's architecture doesn't allow fixing this behavior. The cause of this is that when the SmartRefresh option is disabled, the Grid handles the underlying dataset's notifications. However, the dataset doesn't pass any information on what exactly was changed. That's why the DataController refreshes all data.
Thanks,
Dimitros