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Coordinates of dynamically created items

Posted on 2001-06-18
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Last Modified: 2010-04-06
I wonder if anyone knows how to figure out what coordinates the controls have when they are dynamically created.
I want to create a number of buttons on the canvas and then connect them to each other with lines.
The number of buttons is dynamic and the positions of them are also dynamic and varies with screen size and so on.

Below is a light example of what i want to achieve.

procedure TForm1.Button1Click(Sender: TObject);
Begin
  Vname := Edit1.text;
  Vleft := StrToInt(Edit2.text);
  VTop := StrToInt(Edit3.text);
 
  with TspeedButton.Create(Self) do
  begin
    Parent := Self;
    Left := Vleft;
    Top := Vtop;
    font.Name := 'Arial';
    font.Size := 7;
    Height := 25;
    Width := 42;
    Caption := copy(VName,1,3) + #13 + copy(Vname,4,5);
    Name := Vname;
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  // draw line between the buttons.
  moveto("button with name X".left,"button with name X".top);
  canvas.lineto("button with name Y".left,"button with name Y".top);
  canvas.lineto("button with name Z".left,"button with name Z".top);
  {"And so on"}
end;


Please suggest a good way to do this.
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Question by:samone
  • 3
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6 Comments
 
LVL 5

Expert Comment

by:TheNeil
ID: 6202139
Can't you access the Left and Top properties of the dynamically created objects?

Searching for the component you just created by name isn't really advisable but here goes:

Result := -1;
FOR iCount := 0 TO (Form1.ComponentCount - 1)
DO
  IF Form1.Components[iCount] IS TSpeedButton
  THEN
  BEGIN
    IF (Form1.Components AS TSpeedButton).Name = sSearchName
    THEN
      Result := iCount;
  END;
...

Then you simply need to access the component selected ie:

IF result <> -1
THEN
  Left := (Form1.Components[Result] AS TSpeedButton).Left;
...

The Neil =:)
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LVL 5

Accepted Solution

by:
TheNeil earned 100 total points
ID: 6202158
Oops. Sorry. What you need to do is simply supply the name of the component to the sSearchName variable (type String) and it should search through all of the components on the form (Form1 in this case) looking for a speedbutton with the name required. If you want to search for other component types (e.g.TButton) then you simply need to add additional IF's to check if the component is of the correct type, and then typecast it as that type (Similarly when you get you result value back, typecast the component as the correct type)

The Neil =:)
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Author Comment

by:samone
ID: 6202497
Is there an other way than searching for them to access the left and top values since you say it's not advisable ?
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LVL 5

Expert Comment

by:TheNeil
ID: 6202506
The searching approach is fine, it's just searching by name that isn't ideal. Unfortuneatly in this situation I can't think of a better solution so all I'd say is make extra sure that all of your components are named uniquely and you should have no problems

The Neil =:)
0
 
LVL 9

Expert Comment

by:ITugay
ID: 6202515
Hi samone,

may be easy to put dynamically generated buttons into TList? Then you can easy access those buttons. Here is sample how to draw lines between buttons which is in TList.

type
  TForm1 = class(TForm)
...
  private
  public
    BtnList: TList;
    procedure Paint; override;
  end;

.....

procedure TForm1.FormCreate(Sender: TObject);
begin
  BtnList := TList.Create;
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  BtnList.Free;
end;

// paint lines between buttons
procedure TForm1.Paint;
var
  B: TSpeedButton;
  I: Integer;
begin
  Inherited;
  for I := 0 to BtnList.Count-1 do
  begin
    B := BtnList[I];
    if I <> 0 then
      Canvas.LineTo(B.Left, B.Top);

    Canvas.MoveTo(B.Left + B.Width, B.Top + B.Height);
  end;
end;

// generate random button
procedure TForm1.Button1Click(Sender: TObject);
var
  B: TSpeedButton;
begin
  B := TSpeedButton.Create(Self);
  B.Parent := Self;
  B.Left := Random(10) * (Width div 11);
  B.Top := Random(10) * (Height div 11);
  BtnList.Add(B);
  Invalidate;
end;

------
Igor.

0
 

Author Comment

by:samone
ID: 6202696
Thanks ! for the quick response.
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