Delphi L03 Forms and Input

Intro to Event-driven Programming
and Forms with Delphi
L03 – Forms and Input

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

“Unit”s
Dividing your programs into district “unit”s is useful for
organizing your project

Peek on our “Delphi code area”

Peek on our “Delphi code area”
unit Unit1;

interface

Name of the “unit” we are working in
Libraries we can take functions &
procedures from it

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;
type
TForm1 = class(TForm)
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
implementation
{$R *.dfm}
end.

Types & classes

Public Variables
Here begins the “unit”
implementation

unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs;

type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
end;
end.

Switching between forms
• Create a new “form” in our “current” project:
– File (Menu) > new > form

• Select the main application form:
– Project (Menu) > Options > Forms > Main Form
– select the “main” application form.

• Linking forms:
– Every form has its own “unit”:
• Form1 > unit1.pas
• Form2 > unit2.pas

– If we want:
• form1 to use form2, we add to unit1 (NOT THE CONTRARY):
– uses unit2

• form2 to use form1, we add to unit2 (NOT THE CONTRARY):
– uses unit1

– Watch out
• for “Circular declaration” in interfaces
– i.e: uses unit1 & uses unit2 at the same time in unit

“Events & Properties”
• Some Events:
–
–
–
–
–

Form1.hide;
Form1.show;
Form1.OnClose;
Form1.OnCreate;
Form1.Refresh;

// imp.
// imp.
// imp.

• Some Properties:
– Design time:
• Visible, Enabled, etc.

// Design time

– Runtime:
• Form1.Visibe:= True/False;
• Form1.Enabled:= True/False;

// Runtime
// Runtime

Test it live

KeyBoard Response “Event”s
• Event (Code Sample):
procedure TForm1.FormKeyDown(Sender: TObject; var Key:
Word;Shift: TShiftState);
Begin
if (key = VK_Right) then
// code
else
if (key = VK_Left) then
//code
end;

• Event (1st Code Example): (KeyDown: Down)
procedure TForm2.FormKeyDown(Sender: TObject; var Key: Word;
Shift: TShiftState);
begin
Label1.Caption:='0';
if (key = VK_RIGHT) then
label1.Caption:='1'
else
if (key=VK_LEFT) then
Label1.Caption:='2'
else
if (key=VK_DOWN) then
end;

• Event (2nd Code Example): (KeyDown: UP)
begin
if (key = VK_RIGHT) then
label1.Caption:='1'
else
Label1.Caption:='2'
else
end;

• Event (3rd Code Example): (KeyDown: Left)
var bool1:boolean;
begin
bool1:=false;
if ((key = VK_RIGHT) and (bool1=not(false))) then
label1.Caption:='1'
else
if (bool1=false) then
Label1.Caption:='2'
else
end;

• Event (4th Code Example): (KeyDown: Down)
var bool1:boolean;
begin
bool1:=true;
if ((key = VK_RIGHT) or (bool1=not(false))) then
label1.Caption:='1'
else
Label1.Caption:='2'
else
end;

• Event (5th Code Example): (KeyDown: Down)
var bool1:boolean;
begin
bool1:=true;
if ((key = VK_RIGHT) and (bool1=not(false))) then
label1.Caption:='1'
else
Label1.Caption:='2'
else
end;

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