Delphi L08 Controls at Runtime P2

Mohammad Shakermohammadshakergtr.wordpress.com

Intro to Event-driven Programming and Forms with Delphi@ZGTRShaker

2010, 2011, 2012

Intro to Event-driven Programming and Forms with Delphi

L08 - Instantiate Controls at RuntimePart 2 and other things you need to

know

Instantiate Controls at Runtime


• Let’s look at the “OnClickButton”

procedure TForm2.Button1Click(Sender: TObject);

begin

end;


• Can we Create Our Own “OnClick” Event? – YES Sure we can – But watch out for defining the exact function header as original one

procedure TForm2.ZGTRClick(Sender: TObject);

Begin

End;

Write it yourself


• Let’s have the following Form


• And let’s have the following hand-made Event :D


var i: integer;

Begin

ShowMessage('In My Own Event ');

End;



Var myButton:TButton;

begin

myButton:= TButton.Create(Self);

myButton.Parent:= Panel1;

myButton.Height:= 35;

myButton.Width:= 100;

myButton.Caption:= 'MyCreatedButton';

myButton.OnClick:= ZGTRClick; // WOW:D

end;


Before Clicking the Dynamic Button


• Cool, right?

After Clicking the Dynamic Button


• Another Ex: Let’s Have The following Form


Var

i: integer; // Global Variable


begin

ShowMessage('Am in my own created EVENT (procedure) '

+ Sender.ClassName);

end;

procedure TForm2.FormCreate(Sender: TObject);

begin

i:= 0; // Initialize Variable

end;



begin

ShowMessage('Am in my own created EVENT (procedure) '

+ Sender.ClassName);

end;




myLabel:TLabel;

myEdit:TEdit;

begin



myButton.Height:= 35;

myButton.Width:= 100;

myButton.Caption:= 'MyCreatedButton';

myButton.Top:= i*20;

myButton.OnClick:= ZGTRClick;

i:=i+2;


myLabel:= TLabel.Create(Self);

myLabel.Parent:= Panel1;

myLabel.Caption:= 'MyCreatedLabel';

myLabel.Top:= i*20;

myLabel.OnClick:= ZGTRClick;

i:=i+2;

myEdit:= TEdit.Create(Self);

myEdit.Parent:= Panel1;

myEdit.Text:= 'MyCreatedEdit';

myEdit.Top:= i*20;

myEdit.OnClick:= ZGTRClick;

end;


Cool For Now


Clicking The Button


Clicking The Label


Clicking The Edit


• Another Ex: Let’s have the previous example with the following form and modified “ZGTRClick” is like this.



begin

ShowMessage('i = ' + IntToStr(i));

end;


var i: integer;

Begin

i:=i+1;

End;


• What will happen now when clicking 4 times on any ones of the 3 controls, and then clicking (Show”i”).

Nice Trick :D

• Another Ex:– Let’s see the following Example

Nice Trick :D

var i: integer; // Global Variable



begin

i:= i+1;



myButton.Top:= i*10;

myButton.Left:= 20;

myButton.OnClick:= Button1Click;

end;

procedure TForm2.FormCreate(Sender: TObject);

begin

i:= 0; // Initialize Variable

end;

Nice Trick :D

Clicking “Create” button two times

After ThatClicking any ones

of created buttons

Array of Objects

Array of Objects

• Declaration

X: Array of String;

M: Array of Array of Integer;

Array of Objects

Array of Objects

• Let’s have the following from design

Array of Objects


var ButtonArr: Array of TButton;

begin

try

SetLength(ButtonArr,StrToInt(Edit1.Text));

for I:= 0 to StrToInt(Edit1.Text)-1 do

Begin

ButtonArr[i]:= TButton.Create(Self);

ButtonArr[i].Parent:= Panel1;

ButtonArr[i].Top:= i*30;

ButtonArr[i].Left:= 10;

End;

except

on e: Exception do

ShowMessage('Re-Enter an Integer value.');

end;

end;

Array of Objects

• Controls created at Runtime!

Exception Handling

• Let’s have the following Example

Exception Handling


var Ptr: ^Integer;

begin

new(Ptr);

Edit1.Text:= IntToStr(Ptr^);

Ptr^:= 3;


end;

Exception Handling


var Ptr: ^Integer;

begin


Ptr^:= 3;


end;

Runtime Error

// Here’s The Error

Exception Handling


var Ptr: ^Integer;

begin


end;

No Runtime Error

Exception Handlingthe concept

Exception Handling

• The structure of exception handlingtry

// Code which may raise an exception.

except

on e:Exception do

begin

// Handle exception “e”

end;

finally

// Code which will be executed whether or not an exception is caught

end;

Exception Handling


var Ptr: ^Integer;

i: integer;

begin

try

// Note that there’s no need for Begin-End In try Statement


Ptr^:= 3;


except

on e: Exception do

ShowMessage('Go away , my program is right No bugs in my code:@

, ente el ajdab:D');

end;

end;

Exception Handling

Exception Handling


var Ptr: ^Integer;

i: integer;

begin

try


except

on e: Exception do



end;

end;

• No Msg

Exception Handling

• No Msg


var Ptr: ^Integer;

i: integer;

begin

try

i:= Ptr^;

except

on e: Exception do



end;

end;

Exception Handling

• Cool!procedure TForm2.Button1Click(Sender: TObject);

var i: integer;

begin

try

i:= StrToInt(Edit1.Text);

except

on e: Exception do

ShowMessage(‘ Re-Enter Integer value. ‘);

end;

end;

Delphi Console ApplicationCan be used for testing, checking algorithms, tracking

variables before deploying your project into forms.

Delphi Console Application


program Project2;

{$APPTYPE CONSOLE}

uses

SysUtils;

begin

try

{ TODO -oUser -cConsole Main: Insert code here }

except

on E:Exception do

Writeln(E.Classname, ': ', E.Message);

end;

end.

Delphi Console Applicationprogram Project2;

{$APPTYPE CONSOLE}

uses

SysUtils;

Var

x:integer;

begin

try

{ TODO -oUser -cConsole Main: Insert code here }

except

on E:Exception do

Writeln(E.Classname, ': ', E.Message);

end;

Readln(x);

Writeln('x = ', x);

Readln;

end.

And.. end of course

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Delphi L08 Controls at Runtime P2

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