Delphi L07 Controls at Runtime P1

Intro to Event-driven Programming
and Forms with Delphi
L07 - Creating Controls at Runtime
Part 1

Mohammad Shaker
mohammadshakergtr.wordpress.com
Intro to Event-driven Programming and Forms with Delphi
@ZGTRShaker
2010, 2011, 2012

Creating Controls at Runtime
• Let’s have the following form design

•We declare the “control” like any other variable
var i: Integer;
var TempShape:TShape;

procedure TForm2.Button1Click(Sender: TObject);
begin
// Now we initialize the shape to use it as a NORMAL
// one
TempShape:= TShape.Create(self);
End;

• Compiler Error
– Tshape is undeclared type

• So don’t forget to add ExtCtrls.
uses
Windows, Messages, SysUtils, Variants, Classes,
Graphics, Controls, Forms, Dialogs, StdCtrls,
ExtCtrls;

•Compile and Run but no shape outputted after writing the

following code.
– What’s messing?
Var TempShape:Tshape;
begin
// Now we initialize the shape to use it as a NORMAL
// one
TempShape:= Tshape.Create(self);
End;

begin
TempShape.Parent:= Panel1;
end;

begin
TempShape.Parent:= Panel1;
TempShape.Shape:= stEllipse;
TempShape.Height:= 100;
TempShape.Width:= 50;
TempShape.Left:= 100;
TempShape.Top:= 50;
TempShape.Brush.Color:= 255;
end;

var i: integer;
ShapeArr: Array [1..5] of TShape;
begin
for i:= 1 to 5 do
Begin
ShapeArr[i]:= TShape.Create(self);
ShapeArr[i].Parent:= Panel1;
ShapeArr[i].Brush.Color:= i*100;
ShapeArr[i].Left:= 100;
ShapeArr[i].Top:= i*40;
End;
end;

var
ButtonPtr: ^TButton;
var i: integer;
begin
for i:= 1 to StrToInt(Edit1.Text) do
Begin
new(ButtonPtr);
ButtonPtr^:= TButton.Create(self);
ButtonPtr^.Parent:= Panel1;
ButtonPtr^.Left:= 100;
ButtonPtr^.Top:= i*40;
End;
end;

var i: integer;
myButton: ^TButton;
begin
for i:= 1 to StrToInt(Edit1.Text) do
Begin
new(ButtonPtr);
ButtonPtr^:= TButton.Create(self);
ButtonPtr^.Caption:= 'Button' + IntToStr(i);
ButtonPtr^.Parent:= Panel1;
ButtonPtr^.Left:= 100;
ButtonPtr^.Top:= i*40;
End;
end;

Type TempPtr = ^ TForm;
TempArr = array [1..Cst] of TempPtr;
Var Arr:TempArr;
Var i:integer;
begin
for i:=1 to Cst do
Begin
new(Arr[i]); // as he have said we need to New the ptr
Arr[i]^:= TForm.Create(self);
Arr[i]^.Show();// Now in every count a new form will be
// created and showed
End;
End;

Type TempPtr = ^ TForm;
TempArr = array [1..Cst] of TempPtr;
Var Arr:TempArr;
Var i:integer;
begin
for i:=1 to Cst do
Begin
// new(Arr[i]);
Arr[i]^:= TForm.Create(self);
Arr[i]^.Show();// Now in every count a new form will be
// created and showed
End;
End;


Type
PtrTemp=^Rcd;
Rcd=record
ShapePtr:^Tshape;
Next:PtrTemp;
end;
Var ls,s,Cruiser:PtrTemp;
// we assume that we have the procedure INSERT already

procedure TForm1.Timer1Timer(Sender: TObject);
Begin
new(s);
new(s^.ShapePtr);
s^.ShapePtr^:= TShape.Create(self);
s^.ShapePtr^.Parent:= Panel1;
s^.ShapePtr^.Show();
s^.ShapePtr^.width:=10;
insert(ls,s);
end;

procedure TForm1.Timer1Timer(Sender: TObject);
Begin
new(s);
insert(ls,s);
new(s^.ShapePtr);
s^.ShapePtr^:= TShape.Create(self);
s^.ShapePtr^.Parent:= Panel1;
s^.ShapePtr^.Show();
s^.ShapePtr^.width:=10;
End;

Begin
Cruiser:=ls;
While (Cruiser<>nil) do
begin
Cruiser^.ShapePtr:= Shape1;
// Compile Errorincompatible types
Cruiser:= Cruiser^.Next;
end;
end;

Begin
new(Cruiser);
Cruiser:=ls;
While Cruiser<>nil do
begin
Cruiser^.ShapePtr^:= Shape1;
end;
end;
// This will result in all the list (ShapePtr) pointers to be
pointing to the static shape(Shape1).

Begin
new(Cruiser);
Cruiser:=ls;
begin
Cruiser^.ShapePtr^:= Button1;
end;
end;
// Compiler Error. incompatible types
// TButton and Tshape are different from each other

Begin
new(Cruiser);
Cruiser:=ls;
begin
Cruiser^.ShapePtr^.Width:= Cruiser^.ShapePtr^.Width+10;
end;
end;
// This will result in increase of the width of all
// shapes of the list by 10 Cool

Delphi L07 Controls at Runtime P1

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Delphi L07 Controls at Runtime P1