Question

My application should generate a random sum calculate the answer then put it in a edit box on a panel and then the panel should move down and repeat (I have done all of this). OK the problem is while the panel is moving down nothing else works it is as if everything is disabled.

unit Unit5;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, jpeg, ExtCtrls, StdCtrls, math, Buttons;

type
  TForm1 = class(TForm)
    Image1: TImage;
    Panel1: TPanel;
    Edit1: TEdit;
    Panel6: TPanel;
    Shape1: TShape;
    Panel7: TPanel;
    Label1: TLabel;
    Edit6: TEdit;
    Label2: TLabel;
    Button1: TButton;
    Image5: TImage;
    Edit7: TEdit;
    Image2: TImage;
    Label3: TLabel;
    Timer1: TTimer;
    procedure FormActivate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure Image2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation
 var hori : integer;
     vert : integer;
     back : integer;
     value1 : integer;
     value2 : integer;
     answer : integer;
     star: integer;
     stranswer: string;
     k : integer;
{$R *.dfm}

procedure TForm1.FormActivate(Sender: TObject);
begin
 panel1.hide;
 panel7.Hide;
 back:=0;
 star:=0;
 end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 stranswer:= inttostr(answer);
 if edit6.Text=stranswer then
 begin
  star:=star+1;
  edit7.text:=inttostr(star);

 end;
 button1.Caption:='Next';
 panel7.Show;
 edit6.SetFocus;
 panel1.show;
 randomize;
 hori:=random(840);
 value1:=random(10);
 value2:=random(10);
 panel1.Top:=0;
 panel1.Left:=hori;
 update;
 answer:=value1+value2;
 edit1.text:=('                '+inttostr(value1)+' + '+inttostr(value2));
 for k:= 1 to 512 do
  begin
   vert:= vert+1;
   panel1.Top:= vert;
   update;
   sleep(50)
  end;
end;

procedure TForm1.Image2Click(Sender: TObject);
begin
  back:=1;
  form5.Close;
  button1.show;
end;

end.

If you want I can send you a picture of the form.
If you can please help me.

Answer 1

You move the panel down in 512 single pixel steps with a 50ms sleep in between each step. Since you don’t process any messages in that time, your app will be unresponsive for the 25s it takes to animate the panel. The program hangs because you have failed to service the message queue.

The solution is to use a timer rather than a loop. In Button1Click you need to start the timer ticking.

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

procedure TForm1.StartPanelAnimation;
begin
  Panel1.Top := 0;
  Timer1.Interval := 50;
  Timer1.Enabled := True;
end;

The timer procedure is like this:

procedure TForm1.PanelAnimationTimerTimer(Sender: TObject);
begin
  DoPanelAnimationStep;
  if PanelAnimationComplete then
    PanelAnimationTimer.Enabled := False;
end;

These functions would look like this:

procedure TForm1.DoPanelAnimationStep;
begin
  Panel1.Top := Panel1.Top+1;
end;

function TForm1.PanelAnimationComplete: Boolean;
begin
  Result := Panel1.Top=512;
end;