delphi - 如何在线程终止后自动执行FreeAndNill()

Question

目前我正在使用额外的线程来很好地释放线程后的内存。在你问之前。不，我不能使用 FreeOnTerminate:=true 因为我需要 .waitfor。我还需要 FreeAndNil()，因为只有这样我才能使用Assigned() 检查线程是否正在运行。示例代码。

procedure TForm1.Button1Click(Sender: TObject);
begin  

  SupervisorThread:= TSupervisorThread.Create(True);
  SupervisorThread.FreeOnTerminate:=false; //MUST BE FALSE!
  SupervisorThread.Priority := tpNormal;
  SupervisorThread.Resume;

end;

procedure TSupervisorThread.Execute;
begin

  CleaningThread:= TCleaningThread.Create(True);
  CleaningThread.FreeOnTerminate:=true;
  CleaningThread.Priority := tpNormal;
  CleaningThread.Resume;

  //some loops here

end;

procedure TCleaningThread.Execute;
begin

  if Assigned(SupervisorThread)=true then
  begin
    SupervisorThread.WaitFor;
    FreeAndNil(SupervisorThread);
  end;

end;

procedure TForm2.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin

  if Assigned(SupervisorThread)=false then CanClose:=true  
  else 
  begin
    CanClose:=false;
    ShowMessage('Cannot close form because SiupervisorThread is still working'); 
  end;

end;

Answer 1

使用TThread.OnTerminate事件:

private
  procedure DoTerminateEvent(Sender: TObject);

var
  isRunning: Boolean;

procedure TForm2.DoTerminateEvent(Sender: TObject);
begin
  isRunning := False;
end;

procedure TForm2.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
  if (isRunning) then
  begin
    CanClose := false;
    ShowMessage('Cannot close form because SupervisorThread is still working')
  end else
    CanClose := true;
end;

创建线程时设置OnTerminate处理程序:

SupervisorThread := TSupervisorThread.Create(True);
...
SupervisorThread.OnTerminate := DoTerminateEvent;
SupervisorThread.Resume;

或者，将其作为参数传递给线程的构造函数:

TSupervisorThread = class(TThread)
public
  constructor Create(OnTerminatEvent: TNotifyEvent);
end;

procedure TThreadCustom.Create(OnTerminateEvent: TNotifyEvent);
begin
  inherited Create(True);
  OnTerminate := OnTerminateEvent;
end;

SupervisorThread := TSupervisorThread.Create(DoTerminateEvent);