Call the UpdateItems
method after you've arranged the columns. E.g.:
..
col.Index := number;
listview.UpdateItems(0, MAXINT);
..
Update:
In my tests, I still seem to need the above call in some occasion. But the real problem is that "there is a bug in the Delphi list view control".
Duplicating the problem with a simple project:
- Place a
TListView
control on a VCL form, set its ViewStyle
to 'vsReport' and set FullDrag
to 'true'.
- Put the below code to the
OnCreate
handler of the form:
ListView1.Columns.Add.Caption := 'col 1';
ListView1.Columns.Add.Caption := 'col 2';
ListView1.Columns.Add.Caption := 'col 3';
ListView1.AddItem('cell 1', nil);
ListView1.Items[0].SubItems.Add('cell 2');
ListView1.Items[0].SubItems.Add('cell 3');
- Place a
TButton
on the form, and put the below code to its OnClick
handler:
ListView1.Columns.Add.Caption := 'col 4';
- Run the project and drag the column header of 'col 3' to in-between 'col 1' and 'col 2'. The below picture is what you'll see at this moment (everything is fine):
- Click the button to add a new column, now the list view becomes:
Notice that 'cell 2' has reclaimed its original position.
Bug:
The columns of a TListView
(TListColumn
) holds its ordering information in its FOrderTag
field. Whenever you change the order of a column (either by setting the Index
property or by dragging the header), this FOrderTag
gets updated accordingly.
Now, when you add a column to the TListColumns
collection, the collection first adds the new TListColumn
and then calls the UpdateCols
method. The below is the code of the UpdateCols
method of TListColumns
in D2007 VCL:
procedure TListColumns.UpdateCols;
var
I: Integer;
LVColumn: TLVColumn;
begin
if not Owner.HandleAllocated then Exit;
BeginUpdate;
try
for I := Count - 1 downto 0 do
ListView_DeleteColumn(Owner.Handle, I);
for I := 0 to Count - 1 do
begin
with LVColumn do
begin
mask := LVCF_FMT or LVCF_WIDTH;
fmt := LVCFMT_LEFT;
cx := Items[I].FWidth;
end;
ListView_InsertColumn(Owner.Handle, I, LVColumn);
Items[I].FOrderTag := I;
end;
Owner.UpdateColumns;
finally
EndUpdate;
end;
end;
The above code removes all columns from the underlying API list-view control and then inserts them anew. Notice how the code assigns each inserted column's FOrderTag
the index counter:
Items[I].FOrderTag := I;
This is the order of the columns from left to right at that point in time. If the method is called whenever the columns are ordered any different than at creation time, then that ordering is lost. And since items do not change their positions accordingly, it all gets mixed up.
Fix:
The below modification on the method seemed to work for as little as I tested, you need to carry out more tests (evidently this fix does not cover all possible cases, see 'torno's comments below for details):
procedure TListColumns.UpdateCols;
var
I: Integer;
LVColumn: TLVColumn;
ColumnOrder: array of Integer;
begin
if not Owner.HandleAllocated then Exit;
BeginUpdate;
try
SetLength(ColumnOrder, Count);
for I := Count - 1 downto 0 do begin
ColumnOrder[I] := Items[I].FOrderTag;
ListView_DeleteColumn(Owner.Handle, I);
end;
for I := 0 to Count - 1 do
begin
with LVColumn do
begin
mask := LVCF_FMT or LVCF_WIDTH;
fmt := LVCFMT_LEFT;
cx := Items[I].FWidth;
end;
ListView_InsertColumn(Owner.Handle, I, LVColumn);
end;
ListView_SetColumnOrderArray(Owner.Handle, Count, PInteger(ColumnOrder));
Owner.UpdateColumns;
finally
EndUpdate;
end;
end;
If you are not using packages you can put a modified copy of 'comctrls.pas' to your project folder. Otherwise you might pursue run-time code patching, or file a bug report and wait for a fix.
Best Answer
I fixed it... after 3 hours of struggling with this.. not understanding why.. I finally saw the light.. CompareFloat was asking if two integers were greater or less than each other.
(Copied and modified from EFG's Delphi site)