Moving controls in a gridpanel with Delphi - delphi

In a previous question here I asked about drag n drop within the gridpanel.
Drag N Drop controls in a GridPanel
The question I have next is that I am having weird behavior whenever I try to move controls diagonally when they are near other controls. Controls that not suppose to move are shifting cells. Up and down, sideways it is fine. But diagonal moves, when the moved cell contents are on the same row/column with other cells which hold controls will cause unexpected shifts. I have tried beginupdate/endupdate the shifts still happen. There is a LOCK function for the gridpanel but lock anything. It happens when the drop is on an empty cell, and even cells that already have contents.
here is the test project (Delphi 2010 w/o exe)
http://www.mediafire.com/?xmrgm7ydhygfw2r
type
TForm1 = class(TForm)
GridPanel1: TGridPanel;
btn1: TButton;
btn3: TButton;
btn2: TButton;
lbl1: TLabel;
procedure FormCreate(Sender: TObject);
private
{ Private declarations }
procedure GridPanelDragDrop(Sender, Source: TObject; X, Y: Integer);
procedure btnDragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
procedure btnDragDrop(Sender, Source: TObject; X, Y: Integer);
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure SetColumnWidths(aGridPanel: TGridPanel);
var
i,pct: Integer;
begin
aGridPanel.ColumnCollection.BeginUpdate;
pct:=Round(aGridPanel.ColumnCollection.Count/100);
for i := 0 to aGridPanel.ColumnCollection.Count - 1 do begin
aGridPanel.ColumnCollection[i].SizeStyle := ssPercent;
aGridPanel.ColumnCollection[i].Value := pct;
end;
aGridPanel.ColumnCollection.EndUpdate;
end;
procedure SetRowWidths(aGridPanel: TGridPanel);
var
i,pct: Integer;
begin
aGridPanel.RowCollection.BeginUpdate;
pct:=Round(aGridPanel.RowCollection.Count/100);
for i := 0 to aGridPanel.RowCollection.Count - 1 do begin
aGridPanel.RowCollection[i].SizeStyle := ssPercent;
aGridPanel.RowCollection[i].Value := pct;
end;
aGridPanel.RowCollection.EndUpdate;
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
btn1.OnDragOver := btnDragOver;
btn2.OnDragOver := btnDragOver;
btn3.OnDragOver := btnDragOver;
GridPanel1.OnDragOver := btnDragOver;
GridPanel1.OnDragDrop := GridPanelDragDrop;
btn1.OnDragDrop := btnDragDrop;
btn2.OnDragDrop := btnDragDrop;
btn3.OnDragDrop := btnDragDrop;
SetColumnWidths(GridPanel1);
SetRowWidths(GridPanel1);
end;
procedure TForm1.btnDragOver(Sender, Source: TObject; X, Y: Integer;
State: TDragState; var Accept: Boolean);
begin
Accept := (Source is TButton);
end;
procedure TForm1.btnDragDrop(Sender, Source: TObject; X, Y: Integer);
var
src_x,src_y, dest_x, dest_y: Integer;
btnNameSrc,btnNameDest: string;
src_ctrlindex,dest_ctrlindex:integer;
begin
if Source IS tBUTTON then
begin
//GridPanel1.ColumnCollection.BeginUpdate;
btnNameSrc := (Source as TButton).Name;
btnNameDest := (Sender as TButton).Name;
src_ctrlindex := GridPanel1.ControlCollection.IndexOf(Source as tbutton);
src_x := GridPanel1.ControlCollection.Items[src_ctrlindex].Column;
src_y := GridPanel1.ControlCollection.Items[src_ctrlindex].Row;
dest_ctrlindex := GridPanel1.ControlCollection.IndexOf(Sender as tbutton);
dest_x := GridPanel1.ControlCollection.Items[dest_ctrlindex].Column;
dest_y := GridPanel1.ControlCollection.Items[dest_ctrlindex].Row;
GridPanel1.ControlCollection[src_ctrlindex].Column := dest_x;
GridPanel1.ControlCollection[src_ctrlindex].Row := dest_y;
//GridPanel1.ColumnCollection.EndUpdate;
lbl1.Caption := Format('"%s" from cell %d:%d to Cell %s=%d:%d', [btnNameSrc,src_x,src_y,btnNameDest,dest_x,dest_y]);
end;
end;
procedure TForm1.GridPanelDragDrop(Sender, Source: TObject; X, Y: Integer);
var
DropPoint: TPoint;
CellRect: TRect;
i_col, i_row, src_x,src_y, dest_x, dest_y: Integer;
btnNameSrc,btnNameDest: string;
src_ctrlindex:integer;
begin
if Source is tbutton then
begin
btnNameSrc := (Source as TButton).Name;
btnNameDest := '';
src_ctrlindex := GridPanel1.ControlCollection.IndexOf(Source as tbutton);
src_x := GridPanel1.ControlCollection.Items[src_ctrlindex].Column;
src_y := GridPanel1.ControlCollection.Items[src_ctrlindex].Row;
DropPoint := Point(X, Y);
for i_col := 0 to GridPanel1.ColumnCollection.Count-1 do
for i_row := 0 to GridPanel1.RowCollection.Count-1 do
begin
CellRect := GridPanel1.CellRect[i_col, i_row];
if PtInRect(CellRect, DropPoint) then
begin
// Button was dropped over Cell[i_col, i_row]
dest_x := i_col;
dest_y := i_row;
Break;
end;
end;
lbl1.Caption := Format('"%s" from cell %d:%d to Cell %s=%d:%d', [btnNameSrc,src_x,src_y,btnNameDest,dest_x,dest_y]);
GridPanel1.ControlCollection[src_ctrlindex].Column := dest_x;
GridPanel1.ControlCollection[src_ctrlindex].Row := dest_y;
end;
end;

This is not about dragging, when an item's both column and row are changing the change occurs in two steps. With your code, first the column, then the row. If in the column change, f.i., there happens to be already an other control, this other control is pushed aside, even if its cell is not the ultimate location of the target cell of the moving control.
Begin/EndUpdate will not work, the control collection never checks the update count. What can you do is to use a protected hack to access the control item's InternalSetLocation method. This method has a 'MoveExisting' parameter which you can pass 'False'.
type
THackControlItem = class(TControlItem);
procedure TForm1.GridPanelDragDrop(Sender, Source: TObject; X, Y: Integer);
var
[...]
begin
if Source is tbutton then
begin
[...]
lbl1.Caption := Format('"%s" from cell %d:%d to Cell %s=%d:%d', [btnNameSrc,src_x,src_y,btnNameDest,dest_x,dest_y]);
THackControlItem(GridPanel1.ControlCollection[src_ctrlindex]).
InternalSetLocation(dest_x, dest_y, False, False);
// GridPanel1.ControlCollection[src_ctrlindex].Column := dest_x;
// GridPanel1.ControlCollection[src_ctrlindex].Row := dest_y;
end;
end;
You might need to test if the target cell is empty or not before calling 'InternalSetLocation' depending on what you expect to be the correct control movement.

I use a quite different way to do the Job... Create a whole unit just to add a method to ExtCtrls.TControlCollection without touching unit ExtCtrls (first hack) and make such method use InternalSetLocation (second hack). I also explain both hacks on this post.
Then i only need to add such unit to implementation uses section (before gridpanel declaration) and call the method i created... very simple to use.
Here is how i do it, step by step:
I include such unit i maded for such job to the project (add file)
I add to my TForm interface uses section such unit (or where i need it)
I use my method AddControlAtCell instead of ExtCtrls.TControlCollection.AddControl
Here is the unit i had created for such job, save it as unitTGridPanel_WithAddControlAtCell:
unit unitTGridPanel_WithAddControlAtCell;
interface
uses
Controls
,ExtCtrls
;
type TGridPanel=class(ExtCtrls.TGridPanel)
private
public
procedure AddControlAtCell(AControl:TControl;AColumn:Integer;ARow:Integer); // Add Control on specifed cell, if there already exists a Control it will be deleted
end;
implementation
uses
SysUtils
;
type
THackControlItem=class(TControlItem); // To get internal access to InternalSetLocation procedure
procedure TGridPanel.AddControlAtCell(AControl:TControl;AColumn:Integer;ARow:Integer);
var
TheControlItem:TControlItem; // To let it be added in a specified cell, since ExtCtrls.TControlCollection.AddControl contains multiply BUGs
begin // Add Control on specifed cell, if there already exists a Control it will be deleted
if (-1<AColumn)and(AColumn<ColumnCollection.Count) // Cell with valid Column
and // Cell inside valid range
(-1<ARow)and(ARow<RowCollection.Count) // Cell with valid Row
then begin // Valid cell, must check if there is already a control
if (Nil<>ControlCollection.ControlItems[AColumn,ARow]) // Check if there are any controls
and // A control is already on the cell
(Nil<>ControlCollection.ControlItems[AColumn,ARow].Control) // Check if cell has a control
then begin // There is already a control, must be deleted
ControlCollection.Delete(ControlCollection.IndexOf(ControlCollection.ControlItems[AColumn,ARow].Control)); // Delete the control
end;
TheControlItem:=ControlCollection.Add; // Create the TControlItem
TheControlItem.Control:=TControl(AControl); // Put the Control in the specified cell without altering any other cell
THackControlItem(ControlCollection.Items[ControlCollection.IndexOf(AControl)]).InternalSetLocation(AColumn,ARow,False,False); // Put the ControlItem in the cell without altering any other cell
end
else begin // Cell is out of range
raise Exception.CreateFmt('Cell [%d,%d] out of range on ''%s''.',[AColumn,ARow,Name]);
end;
end;
end.
I hope the comments are enough clear, please read them to understand why and how i do it.
Then, when i need to add a control to the gridpanel at a specified cell i do the next simple call:
TheGridPanel.AddControlAtCell(TheControl,ACloumn,ARow); // Add it at desired cell without affecting other cells
A very, very basic example of adding a runtime newly created TCheckBox at a specific cell could be like this:
// AColumn is of Type Integer
// ARow is of Type Integer
// ACheckBox is of Type TCheckBox
// TheGridPanel is of Type TGridPanel
ACheckBox:=TCheckBox.Create(TheGridPanel); // Create the Control to be added (a CheckBox)
ACheckBox.Visible:=False; // Set it to not visible, for now (optimization on speed, e tc)
ACheckBox.Color:=TheGridPanel.Color; // Just to use same background as on the gridpanel
ACheckBox.Parent:=TheGridPanel; // Set the parent of the control as the gridpanel (mandatory)
TheGridPanel.AddControlAtCell(ElCheckBox,ACloumn,ARow); // Add it at desired cell without affecting other cells
ElCheckBox.Visible:=True; // Now it is added, make it visible
ElCheckBox.Enabled:=True; // And of course, ensure it is enabled if needed
Please Note that i use this two Hacks:
type THackControlItem let me access the method InternalSetLocation.
type TGridPanel=class(ExtCtrls.TGridPanel) let me add a method to ExtCtrls.TGridPanel without even touching (neither needing source of ExtCtrls)
Important: Also note that i mention it requieres to add the unit to the uses of the interface of each form where you want to use the method AddControlAtCell; that is for normal people, advanced people could also create another unit, etc... the 'concept' is to have the unit on the uses before the declaration of the GridPanel where you wnat to use it... example: if GridPanel is putted at design time on a form... it must go on implementation uses of such form unit.
Hope this helps some one else.

The solution below works without any kind of hacking.
My code is in C++ Builder but i think it is simply to understand for Delphi users because it rely only on VCL functions.
PS: note that I drag TPanels instead of TButtons (a very minor change).
void TfrmVCL::ButtonDragDrop(TObject *Sender, TObject *Source, int X, int Y)
{
TRect CurCellRect;
TRect DestCellRect;
int Col;
int Row;
int destCol; int destRow;
int srcIndex; int destIndex;
TPanel *SrcBtn;
TPanel *DestBtn;
SrcBtn = dynamic_cast<TPanel *>(Source);
if (SrcBtn)
{
int ColCount = GridPnl->ColumnCollection->Count ;
int RowCount = GridPnl->RowCollection->Count ;
// SOURCE
srcIndex = GridPnl->ControlCollection->IndexOf( SrcBtn );
// DESTINATION
// we get coordinates of the button I drag onto
DestBtn= dynamic_cast<TPanel *>(Sender);
if (!DestBtn) return;
destIndex = GridPnl->ControlCollection->IndexOf( DestBtn );
destCol = GridPnl->ControlCollection->Items[ destIndex ]->Column; // the column for the dragged button
destRow = GridPnl->ControlCollection->Items[ destIndex ]->Row;
DestCellRect = GridPnl->CellRect[ destCol ][ destRow ];
// Check all cells
for ( Col = 0 ; Col < ColCount ; Col++ )
{
for ( Row = 0 ; Row < RowCount ; Row++ )
{
// Get the bounding rect for this cell
CurCellRect = GridPnl->CellRect[ Col ][ Row ];
if (IntersectRect_ForReal(DestCellRect, CurCellRect))
{
GridPnl->ControlCollection->Items[srcIndex]->SetLocation(Col, Row, false);
return;
}
}
}
}
}

Related

Update corresponding label depending on which combobox fired the event

I have a program with n ComboBoxes and n Labels and I want to update the corresponding Label depending on the selection from the adjacent ComboBox i.e ComboBox2 would update Label2.
I am using the same event handler for every ComboBox and currently checking if Combobox1 or Combobox2 has fired the event handler. Is there a way to use the ItemIndex of the ComboBox passed to the procedure, such as Sender.ItemIndex? This is not currently an option and gives the error 'TObject' does not contain a member named 'ItemIndex'.
procedure TForm2.ComboBoxChange(Sender: TObject);
begin
if Sender = ComboBox1 then
Label1.Caption := ComboBox1.Items.Strings[ComboBox1.ItemIndex]
else
Label2.Caption := ComboBox2.Items.Strings[ComboBox2.ItemIndex];
end;
This code has the desired behavior but is obviously not scale-able.
Every component has a Tag property inherited from TComponent, where the Tag is a pointer-sized integer. As such, you can store each TLabel pointer directly in the corresponding TComboBox.Tag, eg:
procedure TForm2.FormCreate(Sender: TObject);
begin
ComboBox1.Tag := NativeInt(Label1);
ComboBox2.Tag := NativeInt(Label2);
end;
This way, ComboBoxChange() can then directly access the TLabel of the changed TComboBox, eg:
procedure TForm2.ComboBoxChange(Sender: TObject);
var
CB: TComboBox;
begin
CB := TComboBox(Sender);
if CB.Tag <> 0 then
TLabel(CB.Tag).Caption := CB.Items.Strings[CB.ItemIndex];
end;
Option 1
This is the most robust one.
Let your form have private members
private
FControlPairs: TArray<TPair<TComboBox, TLabel>>;
procedure InitControlPairs;
and call InitControlPairs when the form is created (either in its constructor, or in its OnCreate handler):
procedure TForm1.InitControlPairs;
begin
FControlPairs :=
[
TPair<TComboBox, TLabel>.Create(ComboBox1, Label1),
TPair<TComboBox, TLabel>.Create(ComboBox2, Label2),
TPair<TComboBox, TLabel>.Create(ComboBox3, Label3)
]
end;
You need to add the controls to this array manually. That's the downside of this approach. But you only need to do this once, right here. Then everything else can be done automagically.
Now, this is where it gets really nice: Let all your comboboxes share this OnChange handler:
procedure TForm1.ComboBoxChanged(Sender: TObject);
var
i: Integer;
begin
for i := 0 to High(FControlPairs) do
if FControlPairs[i].Key = Sender then
FControlPairs[i].Value.Caption := FControlPairs[i].Key.Text;
end;
Option 2
Forget about any private fields. Now instead make sure that each pair has a unique Tag. So the first combo box and label both have Tag = 1, the second pair has Tag = 2, and so on. Then you can do simply
procedure TForm1.ComboBoxChanged(Sender: TObject);
var
TargetTag: Integer;
CB: TComboBox;
i: Integer;
begin
if Sender is TComboBox then
begin
CB := TComboBox(Sender);
TargetTag := CB.Tag;
for i := 0 to ControlCount - 1 do
if (Controls[i].Tag = TargetTag) and (Controls[i] is TLabel) then
begin
TLabel(Controls[i]).Caption := CB.Text;
Break;
end;
end;
end;
as the shared combo-box event handler. The downside here is that you must be sure that you control the Tag properties of all your controls on the form (at least with the same parent as your labels). Also, they must all have the same parent control.

StringGrid Cells Delphi

I've written some code which colours individual cells on my stringgrid, within my delphi application, according to a list of data.
I now need to write some code in the OnDblClick event on my stringgrid which deduces whether or not a cell is coloured and then proceeds according to the result found. For instance:
DOUBLE CLICK CELL
IS CELL COLOURED
YES > PROCEED A
NO > PROCEED B
Store the color at the time you draw it into the predefined TStringGrid.Objects property. When you need to retrieve it, you can get it back from the Column and Row coordinates. Here's a trivial example that stores either clWhite or clBlack in the Objects for the cell based on whether or not it's an odd-numbered column, and simply displays the stored value as a string when the cell is selected. It should get you started.
procedure TForm1.FormCreate(Sender: TObject);
var
r, c: Integer;
const
ColorSel: array[Boolean] of TColor = (clWhite, clBlack);
begin
StringGrid1.RowCount := 10;
StringGrid1.ColCount := 6;
for c := 1 to StringGrid1.ColCount - 1 do
for r := 1 to StringGrid1.RowCount - 1 do
begin
StringGrid1.Cells[c, r] := Format('C: %d R: %d', [c, r]);
StringGrid1.Objects[c, r] := TObject(ColorSel[Odd(c)]);
end;
end;
procedure TForm1.StringGrid1SelectCell(Sender: TObject; ACol, ARow: Integer;
var CanSelect: Boolean);
begin
ShowMessage(ColorToString(TColor(StringGrid1.Objects[ACol, ARow])));
end;
You can use this in the OnMouseUp event easily to detect what color is in the cell. Remove the StringGrid1SelectCell (using the Object Inspector, just remove the value for the event) and add this as the OnMouseUp event for the grid instead:
procedure TForm1.StringGrid1MouseUp(Sender: TObject; Button: TMouseButton;
Shift: TShiftState; X, Y: Integer);
var
Col, Row: Integer;
begin
StringGrid1.MouseToCell(X, Y, Col, Row);
if (Col > -1) and (Row > -1) then
ShowMessage(ColorToString(TColor(StringGrid1.Objects[Col, Row])));
end;
Handling the double-click then becomes pretty easy (thanks to #TLama for a big assist):
procedure TForm1.StringGrid1DblClick(Sender: TObject);
var
IsDefaultColor: Boolean;
CurrCellColor: TColor;
CurrCol, CurrRow: Integer;
begin
// Save typing by grabbing the currently selected cell col/row
CurrCol := StringGrid1.Col;
CurrRow := StringGrid1.Row;
// Get the stored color for the selected cell
CurrCellColor := TColor(StringGrid1.Objects[CurrCol, CurrRow]);
// See if it's been painted a different color than the default
IsDefaultColor := (CurrCellColor = StringGrid1.Color);
if not IsDefaultColor then
HandleDifferentColorCell
else
HandleNormalColorCell;
end;
Note that if you're choosing not to change the color for a cell, you should still assign the default color of the cell to the Objects[Column, Row] so that there's something meaningful there in order to avoid an improper conversion when retrieving the value.

Delphi TGridPanel - dynamically hide some rows

I have grid panel 16 x 4 like this one:
Sometimes i want to hide some rows and to move bottom rows up. When I set component visible property to false the layout is not updated:
Nevertheless the row size type is set to auto:
Why the component don't set row height to zero when there is nothing to display?
Why the component don't set row height to zero when there is nothing to display ?
Because the row is considered as empty only if there are no components in all columns in that row, not if they're visible or not. So the same returns the IsRowEmpty method. To workaround this, you'd need to be notified by the cell component about its visibility change. When this notification is generated, you can check the row just like the IsRowEmpty method does, except you'll check if the controls are visible, not if they're assigned. Based on the result of such method, you can then set the size of the Value to 0 to hide the row.
With a help of interposed class, the method for checking if all controls in a row or column are visible, you might write something like this. Those methods return True, when all existing controls in a certain row or column are visible, False otherwise:
uses
ExtCtrls, Consts;
type
TGridPanel = class(ExtCtrls.TGridPanel)
public
function IsColContentVisible(ACol: Integer): Boolean;
function IsRowContentVisible(ARow: Integer): Boolean;
end;
implementation
function TGridPanel.IsColContentVisible(ACol: Integer): Boolean;
var
I: Integer;
Control: TControl;
begin
Result := False;
if (ACol > -1) and (ACol < ColumnCollection.Count) then
begin
for I := 0 to ColumnCollection.Count -1 do
begin
Control := ControlCollection.Controls[I, ACol];
if Assigned(Control) and not Control.Visible then
Exit;
end;
Result := True;
end
else
raise EGridPanelException.CreateFmt(sInvalidColumnIndex, [ACol]);
end;
function TGridPanel.IsRowContentVisible(ARow: Integer): Boolean;
var
I: Integer;
Control: TControl;
begin
Result := False;
if (ARow > -1) and (ARow < RowCollection.Count) then
begin
for I := 0 to ColumnCollection.Count -1 do
begin
Control := ControlCollection.Controls[I, ARow];
if Assigned(Control) and not Control.Visible then
Exit;
end;
Result := True;
end
else
raise EGridPanelException.CreateFmt(sInvalidRowIndex, [ARow]);
end;
And the usage shown for the first row:
procedure TForm1.Button1Click(Sender: TObject);
begin
// after you update visibility of controls in the first row...
// if any of the controls in the first row is not visible, change the
// row's height to 0, what makes it hidden, otherwise set certain height
if not GridPanel1.IsRowContentVisible(0) then
GridPanel1.RowCollection[0].Value := 0
else
GridPanel1.RowCollection[0].Value := 50;
end;
I've got a hacky solution ... keeping the Autosizing
Procedure ShowHideControlFromGrid(C:TControl);
begin
if C.Parent = nil then
begin
c.Parent := TWinControl(c.Tag)
end
else
begin
c.Tag := NativeInt(C.Parent);
c.Parent := nil;
end;
end;
procedure TForm4.Button1Click(Sender: TObject);
begin // e.g. Call
ShowHideControlFromGrid(Edit5);
ShowHideControlFromGrid(Edit6);
ShowHideControlFromGrid(Edit7);
ShowHideControlFromGrid(Label1);
end;

creating checkbox

I am trying to create a few checkboxes, how many is decided by the recordcount of a query. Also i need to set the loction of the check box +38 from the previous location. Anyone give me some help with this? not sure how to create the checkboxes, The rest i should be able to do...anyhow he is what i have so far.
var
i, top,left : integer;
begin
......
left := 81;
top := 119;
while i < qry.RecordCount do
begin
// create check box
// set caption of checkbox to i
// set checkbox loction to left + 38, top
// left = left+38??
end;
After clarifying your needs, I would recommend you to use TObjectList as a container for your check boxes. This list can own the objects, what allows you to release them by a simple removing the item from the list either by Clear or by Delete. It also provides a simple access to each element by typecasting the obtained indexed item object to your known class type. More in the following untested pseudo-code:
uses
Contnrs;
type
TForm1 = class(TForm)
procedure FormCreate(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
CheckList: TObjectList;
public
{ Public declarations }
end;
procedure TForm1.FormCreate(Sender: TObject);
begin
CheckList := TObjectList.Create;
// setting OwnsObjects to True will ensure you, that the objects
// stored in a list will be freed when you delete them from list
CheckList.OwnsObjects := True;
end;
procedure TForm1.FormDestroy(Sender: TObject);
begin
// this will also release all check boxes thanks to OwnsObjects
CheckList.Free;
end;
procedure TForm1.Button1Click(Sender: TObject);
var
I: Integer;
CheckBox: TCheckBox;
begin
...
CheckList.Clear; // this will free all check boxes
for I := 0 to RecordCount - 1 do // iterate over your recordset
begin
CheckBox := TCheckBox.Create(nil); // be sure to use nil as an owner
CheckBox.Parent := Self; // where will be laying (Self = Form)
CheckBox.Caption := IntToStr(I); // caption by the iterator value
CheckBox.Top := 8; // fixed top position
CheckBox.Left := (I * 38) + 8; // iterator value * 38 shifted by 8
CheckBox.Width := 30; // fixed width
CheckList.Add(CheckBox); // add the check box to the list
end;
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
// this will check the first check box from the list (be careful to indexes)
TCheckBox(CheckList.Items[0]).Checked := True;
// this will delete 3rd check box from the list (using Clear will delete all)
CheckList.Delete(2);
end;
Your pseudo code translates almost literally into Delphi code although it's better to use a for loop here:
for I := 0 to qry.RecordCount-1 do
begin
CheckBox := TCheckBox.Create (Self); // the form owns the checkbox
CheckBox.Parent := Self; // checkbox is displayed on the form
CheckBox.Caption := IntToStr (I);
CheckBox.Top := Top;
CheckBox.Left := 81 + I*38;
end;
BTW, you don't have to free the created checkbox thanks to the ownership mechanism built into the VCL.

Finding out position of a control inside TGridPanel

How I can find out the position (row and column index) of controls inside TGridPanel? I'd like to use common OnClick event for number of buttons and need to know the X,Y position of the button.
I'm using Delphi 2007.
Unfortunately, because of the magic of TGridPanel, it is a little more complicated than just getting the Top and Left properties...
This should do it for any Control, adapt it to your needs:
procedure GetRowColumn(const AControl: TControl; var ARow, AColumn: Integer);
var
I: Integer;
begin
if AControl.Parent is TGridPanel then
begin
I := TGridPanel(AControl.Parent).ControlCollection.IndexOf(AControl);
if I > -1 then
begin
ARow := TGridPanel(AControl.Parent).ControlCollection[I].Row;
AColumn := TGridPanel(AControl.Parent).ControlCollection[I].Column;
end;
end;
end;
procedure TForm1.ButtonClick(Sender: TObject);
var
Row, Column : Integer;
begin
GetRowColumn(Sender as TControl, Row, Column);
// do something with Row and Column
ShowMessage( Format('row=%d - col=%d',[Row, Column]));
end;
You can use Sender cast as a tButton and then ask it for its top and left for example:
Procedure TForm1.OnClick(Sender:tObject);
var
X,Y : Integer;
begin
if Sender is TButton then
begin
X := TButton(Sender).Top;
Y := TButton(Sender).Left;
// do something with X & Y
end;
end;
Or if your just wanting to know what button was pressed, you can also use the TAG property to insert a number into each button, and then retrieve the tag value in your onclick event. Just remember to first set the Tag property to something. You can do this in the form designer if your just dropping buttons into the grid panel or in the routine your using to create and insert your buttons.
Procedure TForm1.OnClick(Sender:tObject);
var
iButton : integer;
begin
if Sender is TComponent then
begin
iButton := TComponent(Sender).Tag;
// do something with iButton
end;
end;
You can also use the tag property to store more than just an integer, since a pointer currently uses the same memory size as the integer you can cast a pointer to an integer and insert that value into the tag property. Just be aware that any pointer you place in this field is still treated as an integer. You are responsible for the memory it points to, it will not be managed by the component.

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