Mega Code Archive
Sort a TListView using the CustomSort method
<![CDATA[
Title: sort a TListView using the CustomSort method?
{
This example shows how to use the TListView's CustomSort method to
sort the items in the list using a ordering function.
This allows you to sort custom data in the correct order you want.
When the user clicks on a column header, the ListView will be sorted
by that column.
If the user clicks on the same column again, the sort order will be toggled.
(***)
Dieses Beispiel zeigt die Verwendung der CustomSort Methode einer TListView.
Damit kann man z.B Zahlen korrekt (d.h nach ihrer Grösse) sortieren lassen.
Wenn der Anwender auf den Kopf einer Spalte klickt, wird die ensprechende
Spalte sortiert. Bei nochmaligem Klicken auf dieselbe Spalte wird die
Sortierreihenfolge umgekehrt.
}
{ custom sort styles }
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 then
s1 := Item1.SubItems[SortColumn];
if (SortColumn 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;
]]>