Multiple Thread Delphi Stop - multithreading

Question

I have a frame, inside it I have a thread, the creation of this front and at runtime, each click that give the button it creates a new frame and may have innumerable within the form. the problem is that ... I create the first, the thread starts normal when I create the second, the first thread to, and the second begins, if I click again, the first and second stand still and the third begins, if I close the third, the second back to work, because this happens?
thank you
constructor TMy_Thread.Create(fraConnect : TfraConnect);
begin
inherited Create(True);
Priority := tpTimeCritical;
FreeOnTerminate := true;
fraConnectT := fraConnect;
end;
procedure TMy_Thread.Execute;
begin
Synchronize(Teste);
end;
procedure TMy_Thread.TEste;
var
iSize : Int64;
iCnt : Integer;
Msg : TMsg ;
begin
inherited;
with fraConnectT do begin
While not Terminated do begin
Log(fraConnectT.Name,'');
Application.ProcessMessages;
end;
end;
end;
////////////////
procedure TfraConnect.Click(Sender: TObject);
var
Sc : TMy_Thread;
begin
Sc := TMy_Thread.Create(Self);
try
iTela := 0;
Sc.Execute;
finally
Sc.Terminate;
end;
end;

Answer 1

You are not using TThread correctly. You are not starting the thread (so it does not free itself when terminated), you are calling Execute() directly, you are Synchronizeing the entire body of Execute(). So Execute() runs in the main thread, calling ProcessMessages() to allow a new button click, which calls Execute() blocking the previous Execute() until the new Execute() exits, and so on. That is why you are experiencing the symptoms you are seeing.
To fix this, you need to do the following:
In the thread constructor, call inherited Create(False) instead. This allows the thread to start running automatically. Otherwise, you have to call the thread's Resume() or Start() method after the constructor exits.
remove Execute() from Click(). Let the running thread call Execute().
remove ProcessMessages() from Teste(). There is never a need to call ProcessMessages() in a thread (unless it is being called inside of Synchronized or Queued code running in the main thread, but even then it should be avoided when possible).
only Synchronize() small code blocks that actually need to run in the main thread - code that does not work in a secondary thread, code that needs to access the UI, code that needs to access a resource shared by multiple threads, etc. The bulk of your thread code should NOT be Synchronized, that defeats the purpose of using a thread in the first place.
Try something more like this:
type
fraConnect = class;
TMy_Thread = class(TThread)
private
fraConnectT : TfraConnect;
procedure DoLog;
protected
procedure Execute; override;
public
constructor Create(fraConnect : TfraConnect);
property Terminated;
end;
...
constructor TMy_Thread.Create(fraConnect : TfraConnect);
begin
inherited Create(True);
Priority := tpTimeCritical;
FreeOnTerminate := true;
fraConnectT := fraConnect;
end;
procedure TMy_Thread.Execute;
begin
with fraConnectT do begin
While not Terminated do begin
// assuming Log() is not thread-safe...
Synchronize(DoLog);
Sleep(100);
end;
end;
end;
procedure TMy_Thread.DoLog;
begin
Log(fraConnectT.Name,'');
end;
type
TMy_Thread = class;
TfraConnect = class(TFrame)
Start: TButton;
Stop: TButton;
StartClick(Sender: TObject);
StopClick(Sender: TObject);
private
Sc: TMy_Thread;
procedure ThreadTerminated(Sender: TObject);
end;
...
procedure TfraConnect.StartClick(Sender: TObject);
begin
if (not Assigned(Sc)) or Sc.Terminated then
begin
Sc := TMy_Thread.Create(Self);
Sc.OnTerminate := ThreadTerminated;
Sc.Resume; // or Sc.Start;
end;
end;
procedure TfraConnect.StopClick(Sender: TObject);
begin
if Assigned(Sc) then
Sc.Terminate;
end;
procedure TfraConnect.ThreadTerminated(Sender: TObject);
begin
if Sc = Sender then
Sc := nil;
end;