Timer process affect the user interface in delphi - delphi

Question

i have developed application for read information from card reader. Here i have used timer for get the information each five second, so every five second the user interface getting slow
because it's get the information from reader. how to run the timer in background with out affecting user interface
unit frmVistorreg;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms;
type
thread1=class(TThread)
private
FEvent: THandle;
protected
procedure Execute; override;
public
procedure MyTerminate;
end;
TForm3 = class(TForm)
txt_name: TEdit;
txt_cardno.Text TEdit;
private
public
end;
var
Form3: TForm3;
implementation
{$R *.dfm}
procedure thread1.Execute;
var
idcard_info :array[0..1024*5] of byte;
flag :Integer;
portflag :Integer;
st :TStrings;
str :string;
begin
FEvent:= CreateEvent(nil, False, false, nil);
try
while not Terminated do begin
if MainForm.PortFlag=0 then
begin
Form3.Label11.Caption:='port has been successfully opened';
Form3.Label11.Font.Color :=32768;
flag := GetIdCardInfo(#idcard_info[0],1024*5,5);
str := byteArray2Str(#idcard_info[0],1024*5);
if(flag=0) then
begin
st := TStringList.Create;
try
SplitStr('^_^',str,st);
Form3.txt_name.Text := st.Strings[0];
Form3.txt_cardno.Text := st.Strings[5];
finally
st.Free;
end;
end;
end
else
begin
Form3.Label11.Caption:='Please open the port';
Form3.Label11.Font.Color:=clRed;
end;
if WaitForSingleObject(FEvent, 500) <> WAIT_TIMEOUT // 5 seconds timeout
then Terminate;
end;
finally
CloseHandle(FEvent);
end;
end;
procedure thread1.MyTerminate;
begin
SetEvent(FEvent);
end;
procedure TForm3.FormClose(Sender: TObject; var Action: TCloseAction);
var
Objthread1:thread1;
begin
Objthread1.MyTerminate;
Action := caFree;
end;
procedure TForm3.FormCreate(Sender: TObject);
var
Objthread1:thread1;
begin
Objthread1:=thread1.Create(false);
end;
end.
when i close the form have error like
Project MDIAPP.exe raised exception class EAccessViolation with message 'Access violation at address 0051B9F1 in module 'MDIAPP.exe'. Read of address 00000198'.
how can i solve this.

Answer 1

You need not a timer component for that, you need a background thread. A simplest solution is to use Sleep function in the thread:
unit Unit2;
interface
uses
Classes;
type
TMyThread = class(TThread)
protected
procedure Execute; override;
end;
implementation
procedure TMyThread.Execute;
begin
while not Terminated do begin
// do your processing here
Sleep(5000); // wait 5 seconds
end;
end;
end.
A better approach is to use WaitForSingleObject and an event instead of Sleep to be able to terminate your background thread immediately without 5 seconds delay:
unit Unit2;
interface
uses
Windows, Classes;
type
TMyThread = class(TThread)
private
FEvent: THandle;
protected
procedure Execute; override;
public
procedure MyTerminate;
end;
implementation
procedure TMyThread.Execute;
begin
FEvent:= CreateEvent(nil, False, False, nil);
try
while not Terminated do begin
// do your processing here
// ..
if WaitForSingleObject(FEvent, 5000) <> WAIT_TIMEOUT // 5 seconds timeout
then Terminate;
end;
finally
CloseHandle(FEvent);
end;
end;
procedure TMyThread.MyTerminate;
begin
SetEvent(FEvent);
end;
end.
To terminate TMyThread instance on closing a form call MyTerminate method from OnClose event handler of a form.
And yes, it is interesting to know what error message you receive, not just 'showing error'.