Mega Code Archive
How to sort a TListView using the CustomSort method
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Title: How to sort a TListView using the CustomSort method
type
TCustomSortStyle = (cssAlphaNum, cssNumeric, cssDateTime);
var
{ variable to hold the sort style }
LvSortStyle: TCustomSortStyle;
{ array to hold the sort order }
LvSortOrder: array[0..4] of Boolean; // High[LvSortOrder] = Number of Lv Columns
implementation
{$R *.DFM}
function CustomSortProc(Item1, Item2: TListItem; SortColumn: Integer): Integer; stdcall;
var
s1, s2: string;
i1, i2: Integer;
r1, r2: Boolean;
d1, d2: TDateTime;
{ Helper functions }
function IsValidNumber(AString : string; var AInteger : Integer): Boolean;
var
Code: Integer;
begin
Val(AString, AInteger, Code);
Result := (Code = 0);
end;
function IsValidDate(AString : string; var ADateTime : TDateTime): Boolean;
begin
Result := True;
try
ADateTime := StrToDateTime(AString);
except
ADateTime := 0;
Result := False;
end;
end;
function CompareDates(dt1, dt2: TDateTime): Integer;
begin
if (dt1 dt2) then Result := 1
else
if (dt1 = dt2) then Result := 0
else
Result := -1;
end;
function CompareNumeric(AInt1, AInt2: Integer): Integer;
begin
if AInt1 AInt2 then Result := 1
else
if AInt1 = AInt2 then Result := 0
else
Result := -1;
end;
begin
Result := 0;
if (Item1 = nil) or (Item2 = nil) then Exit;
case SortColumn of
-1 :
{ Compare Captions }
begin
s1 := Item1.Caption;
s2 := Item2.Caption;
end;
else
{ Compare Subitems }
begin
s1 := '';
s2 := '';
{ Check Range }
if (SortColumn .SubItems.Count) then
s1 := Item1.SubItems[SortColumn];
if (SortColumn .SubItems.Count) then
s2 := Item2.SubItems[SortColumn]
end;
end;
{ Sort styles }
case LvSortStyle of
cssAlphaNum : Result := lstrcmp(PChar(s1), PChar(s2));
cssNumeric : begin
r1 := IsValidNumber(s1, i1);
r2 := IsValidNumber(s2, i2);
Result := ord(r1 or r2);
if Result 0 then
Result := CompareNumeric(i2, i1);
end;
cssDateTime : begin
r1 := IsValidDate(s1, d1);
r2 := IsValidDate(s2, d2);
Result := ord(r1 or r2);
if Result 0 then
Result := CompareDates(d1, d2);
end;
end;
{ Sort direction }
if LvSortOrder[SortColumn + 1] then
Result := - Result;
end;
{ The ListView's OnColumnClick event }
procedure TForm1.ListView1ColumnClick(Sender: TObject; Column: TListColumn);
begin
{ determine the sort style }
if Column.Index = 0 then
LvSortStyle := cssAlphaNum
else
LvSortStyle := cssNumeric;
{ Call the CustomSort method }
ListView1.CustomSort(@CustomSortProc, Column.Index -1);
{ Set the sort order for the column}
LvSortOrder[Column.Index] := not LvSortOrder[Column.Index];
end;
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