Error when you change the order of columns in Dbgrid - delphi

Question

I wrote the code for the form rendering settings database table Dbgrid in another form. It depends on the selected items are defined Chetsklistboks visible columns in Dbgrid. I also wrote the code to move with drag & drop items and columns Chetsklistbox Dbgrid conformity. But start at some point (and in my opinion with an attempt to change the item with the lowest index in the item with a large index) errors when drag & drop from the Argument out of range and when you close the Invalid Pointer Operation. Help resolve the error.
unit SettingOfShowData;
interface
uses
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.CheckLst, Vcl.ExtCtrls,
VirtualTrees, DatabaseClasses, MainForm, ListOfTables;
type
TNodeField=record
NameField : string;
end;
PNodeField=^TNodeField;
type
TfmSettings = class(TForm)
Panel1: TPanel;
VT: TVirtualStringTree;
Edit1: TEdit;
Edit2: TEdit;
Edit3: TEdit;
CheckListBox1: TCheckListBox;
procedure VTGetNodeDataSize(Sender: TBaseVirtualTree;
var NodeDataSize: Integer);
procedure VTGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
Column: TColumnIndex; TextType: TVSTTextType; var CellText: string);
procedure FormCreate(Sender: TObject);
procedure VTFreeNode(Sender: TBaseVirtualTree; Node: PVirtualNode);
procedure FormActivate(Sender: TObject);
function IsPrimaryKey(InputTableName : string; InputFieldName : string) : Boolean;
procedure VTNodeClick(Sender: TBaseVirtualTree; const HitInfo: THitInfo);
procedure VTNodeDblClick(Sender: TBaseVirtualTree; const HitInfo: THitInfo);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
procedure CheckListBox1ClickCheck(Sender: TObject);
procedure CheckListBox1DragDrop(Sender, Source: TObject; X, Y: Integer);
procedure CheckListBox1DragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
procedure CheckListBox1MouseDown(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
private
{ Private declarations }
public
{ Public declarations }
end;
var
fmSettings: TfmSettings;
NumX, NumY : Integer;
implementation
{$R *.dfm}
procedure TfmSettings.CheckListBox1ClickCheck(Sender: TObject);
begin
fmShowData.DBGrid1.Columns[CheckListBox1.ItemIndex].Visible :=
not(fmShowData.DBGrid1.Columns[CheckListBox1.ItemIndex].Visible);
end;
procedure TfmSettings.CheckListBox1DragDrop(Sender, Source: TObject; X,
Y: Integer);
var
Num1, Num2, temp: Integer;
Point1, Point2: TPoint;
begin
Point1.X:=NumX;
Point1.Y:=NumY;
Point2.X:=X;
Point2.Y:=Y;
with Source as TCheckListBox do
begin
Num2:=CheckListBox1.ItemAtPos(Point1,True);
Num1:=CheckListBox1.ItemAtPos(Point2,True);
CheckListBox1.Items.Move(Num2, Num1);
if Num2>Num1 then
begin
temp:=Num2;
Num2:=Num1;
Num1:=temp;
end;
fmShowData.DBGrid1.Columns[Num1].Index:=Num2;
fmShowData.DBGrid1.Columns[Num2+1].Index:=Num1;
end;
end;
procedure TfmSettings.CheckListBox1DragOver(Sender, Source: TObject; X,
Y: Integer; State: TDragState; var Accept: Boolean);
begin
if Source=CheckListBox1 then Accept:=True;
end;
procedure TfmSettings.CheckListBox1MouseDown(Sender: TObject;
Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
NumY:=Y;
NumX:=X;
end;
procedure TfmSettings.FormActivate(Sender: TObject);
var
Index, i: Integer;
VTNodeField : PNodeField;
begin
VT.BeginUpdate();
//TableSpec:=TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable));
for Index := 0 to TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Fields.ComponentCount-1 do
begin
if TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Fields.Components[Index] is TFieldSpec then
begin
VTNodeField:=VT.GetNodeData(VT.AddChild(nil, nil));
VTNodeField^.NameField:=(TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Fields.Components[Index] as TFieldSpec).name;
end;
end;
VT.EndUpdate();
for i := 0 to TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Fields.ComponentCount-1 do
begin
if (TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Fields.Components[i] is TFieldSpec) then
begin
CheckListBox1.Items.Add(TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Fields.Components[i].Name);
CheckListBox1.Checked[i]:=true;
end;
end;
end;
procedure TfmSettings.FormClose(Sender: TObject; var Action: TCloseAction);
var i: integer;
begin
{ while VT.ComponentCount>0 do
begin
VT.DeleteNode(VT.Nodes.GetEnumerator.Current);
VT.DeleteChildren(VT.Nodes.GetEnumerator.Current);
VT.Nodes.GetEnumerator.MoveNext();
end; }
VT.Clear();
//fmTableData.DBGrid1.Columns
CheckListBox1.Clear;
end;
procedure TfmSettings.FormCreate(Sender: TObject);
var
Index: Integer;
VTNodeField : PNodeField;
//TableSpec : TTableSpec;
begin
{ VT.BeginUpdate();
//TableSpec:=TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable));
for Index := 0 to TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).ComponentCount-1 do
begin
if TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Components[Index] is TFieldSpec then
begin
VTNodeField:=VT.GetNodeData(VT.AddChild(nil, nil));
VTNodeField.NameField:=(TTableSpec(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable)).Components[Index] as TFieldSpec).FieldName;
end;
end;
VT.EndUpdate();}
end;
procedure TfmSettings.VTFreeNode(Sender: TBaseVirtualTree; Node: PVirtualNode);
var
Data: PNodeField;
begin
Data:=Sender.GetNodeData(Node);
if Assigned(Data) then
begin
Finalize(Data^);
end;
end;
procedure TfmSettings.VTGetNodeDataSize(Sender: TBaseVirtualTree;
var NodeDataSize: Integer);
begin
NodeDataSize:=SizeOf(TNodeField);
end;
procedure TfmSettings.VTGetText(Sender: TBaseVirtualTree; Node: PVirtualNode;
Column: TColumnIndex; TextType: TVSTTextType; var CellText: string);
var
Index: Integer;
VTNodeField : PNodeField;
begin
VTNodeField:=Sender.GetNodeData(Node);
for Index := 0 to DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable).ComponentCount-1 do
begin
if DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable).Components[Index] is TFieldSpec then
begin
VTNodeField:=Sender.GetNodeData(Sender.AddChild(nil, nil));
VTNodeField^.NameField:=(DBSchema.Tables.FindComponent(fmListOfTables.DisplayTable).Components[Index] as TFieldSpec).name;
end;
end;
CellText:=VTNodeField^.NameField;
end;
procedure TfmSettings.VTNodeClick(Sender: TBaseVirtualTree;
const HitInfo: THitInfo);
var
NewVTNodeField : PNodeField;
NewNode : PVirtualNode;
begin
{NewNode:=VT.AddChild(VT.FocusedNode);
NewVTNodeField:=VT.GetNodeData(NewNode); }
end;
procedure TfmSettings.VTNodeDblClick(Sender: TBaseVirtualTree;
const HitInfo: THitInfo);
var
NewVTNodeField, CurrentNode: PNodeField;
NewNode : PVirtualNode;
//CurrentNode : PDataNode;
i, j : integer;
begin
{ NewNode:=VT.AddChild(VT.FocusedNode);
NewVTNodeField:=VT.GetNodeData(NewNode); }
CurrentNode:=VT.GetNodeData(VT.FocusedNode);
if IsPrimaryKey(fmListOfTables.DisplayTable, {VT.Text[VT.FocusedNode, 0]} CurrentNode^.NameField) then
begin
for i:= 0 to DBSchema.Tables.ComponentCount-1 do
for j:=0 to TTableSpec(DBSchema.Tables.Components[i]).Constraints.ComponentCount-1 do
begin
if (TConstraintSpec(TTableSpec(DBSchema.Tables.Components[i]).Constraints.Components[j]).Reference=fmListOfTables.DisplayTable) then
begin
NewNode:=VT.AddChild(VT.FocusedNode);
NewVTNodeField:=VT.GetNodeData(NewNode);
NewVTNodeField^.NameField:=(TTableSpec(DBSchema.Tables.Components[i])).Name;
end;
end;
end;
end;
function TfmSettings.IsPrimaryKey(InputTableName : string; InputFieldName: string):Boolean;
var
i : integer;
flag: boolean;
begin
flag:=False;
for i:=0 to TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Constraints.ComponentCount-1 do
begin
if ((TConstraintSpec(TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Constraints.Components[i]).ConstraintType='PRIMARY') and (TFieldSpec(TConstraintDetailSpec(TConstraintSpec(TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Constraints.Components[i]).DetailList).FieldSpec).FieldName=InputFieldName){(TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Fields.FindComponent(InputFieldName).Name=TConstraintDetailSpec(TConstraintSpec(TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Constraints.Components[i]).DetailList).FieldName)}) then
flag:=True;
Edit1.Text:=TConstraintSpec(TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Constraints.Components[i]).Name;
Edit2.Text:=AnsiToUtf8(TFieldSpec(TConstraintDetailSpec(TConstraintSpec(TTableSpec(DBSchema.Tables.FindComponent(InputTableName)).Constraints.Components[i]).DetailList).FieldSpec).FieldName);
Edit3.Text:=InputFieldName;
end;
Result:=flag;
end;
end.
Select the code of procedure that changes the order of the columns
procedure TfmSettings.CheckListBox1DragDrop(Sender, Source: TObject; X,
Y: Integer);
var
Num1, Num2, temp: Integer;
Point1, Point2: TPoint;
begin
Point1.X:=NumX;
Point1.Y:=NumY;
Point2.X:=X;
Point2.Y:=Y;
with Source as TCheckListBox do
begin
Num2:=CheckListBox1.ItemAtPos(Point1,True);
Num1:=CheckListBox1.ItemAtPos(Point2,True);
CheckListBox1.Items.Move(Num2, Num1);
if Num2>Num1 then
begin
temp:=Num2;
Num2:=Num1;
Num1:=temp;
end;
fmShowData.DBGrid1.Columns[Num1].Index:=Num2;
fmShowData.DBGrid1.Columns[Num2+1].Index:=Num1;
end;
end;

Answer 1

If then checklistbox is a representation of the fields the corresponding Action for
CheckListBox1.Items.Move(Num2, Num1);
would be
DBGrid1.Columns[num2].Index := DBGrid1.Columns[num1].Index;
nothing more or less.
// Removed comment thx to jachguate