如何根据需要启动/停止监控Delphi线程?

时间:2009-11-14 15:58:07

标签: multithreading delphi ondemand

我一直在寻找一种方法来监控Delphi中特定的注册表更改。在about.com找到solution

procedure TRegMonitorThread.Execute;
begin
  InitThread; // method omitted here
  while not Terminated do
  begin
    if WaitForSingleObject(FEvent, INFINITE) = WAIT_OBJECT_0 then
    begin
      fChangeData.RootKey := RootKey;
      fChangeData.Key := Key;
      SendMessage(Wnd, WM_REGCHANGE, RootKey, LongInt(PChar(Key)));
      ResetEvent(FEvent);

      RegNotifyChangeKeyValue(FReg.CurrentKey, 1, Filter, FEvent, 1);
    end;
  end;
end;

在我的应用程序中,我需要按需启动和停止此线程,但上面的代码不允许这样做。只设置Terminated标志是不行的。

以某种方式告诉线程停止等待,然后释放它并在需要时创建一个新的就足够了。如何更改此代码以实现该目标?

3 个答案:

答案 0 :(得分:8)

WaitForMultipleObjects()与两个事件的数组一起使用,而不是WaitForSingleObject()。将一个手动重置事件添加到线程类,并在将Terminated设置为True后发出信号。检查两个事件中的哪个已发出信号的返回值,并采取相应的行动。

修改

一些最小的Delphi 2009代码来演示这个想法。您必须将SyncObjs添加到已用单位列表中,然后添加

  fTerminateEvent: TEvent;

到线程类的private部分。

constructor TTestThread.Create;
begin
  inherited Create(TRUE);
  fTerminateEvent := TEvent.Create(nil, True, False, '');
  // ...
  Resume;
end;

destructor TTestThread.Destroy;
begin
  fTerminateEvent.SetEvent;
  Terminate; // not necessary if you don't check Terminated in your code
  WaitFor;
  fTerminateEvent.Free;
  inherited;
end;

procedure TTestThread.Execute;
var
  Handles: array[0..1] of THandle;
begin
  Handles[0] := ...; // your event handle goes here
  Handles[1] := fTerminateEvent.Handle;
  while not Terminated do begin
    if WaitForMultipleObjects(2, @Handles[0], False, INFINITE) <> WAIT_OBJECT_0 then
      break;
    // ...
  end;
end;

您只需要在问题中添加代码即可。只需尝试释放线程实例就可以完成解锁线程所需的一切(如有必要)。

答案 1 :(得分:1)

相反,在INFINITE中,你应该在一段时间后让WaitForSingleObject超时。这样循环就会继续,并且会检查终止。

procedure TRegMonitorThread.Execute;
begin
  InitThread; // method omitted here
  while not Terminated do
  begin
    if WaitForSingleObject(FEvent, 1000) = WAIT_OBJECT_0 then
    begin
      fChangeData.RootKey := RootKey;
      fChangeData.Key := Key;
      SendMessage(Wnd, WM_REGCHANGE, RootKey, LongInt(PChar(Key)));
      ResetEvent(FEvent);

      RegNotifyChangeKeyValue(FReg.CurrentKey, 1, Filter, FEvent, 1);
    end;
  end;
end;

方法TThread.Suspend和TThread.Resume理论上可用于临时停止线程,但正如Delphi 2010现在承认它们不安全使用。请参阅TThread.resume is deprecated in Delphi-2010 what should be used in place?http://msdn.microsoft.com/en-us/library/ms686345%28VS.85%29.aspx

答案 2 :(得分:1)

这样做,只需进行如下的小改动,现在当你调用终止时:

  TRegMonitorThread = class(TThread)
  ...
  public
    procedure Terminate; reintroduce;
...

procedure TRegMonitorThread. Terminate;  // add new public procedure
begin
  inherited Terminate;
  Windows.SetEvent(FEvent);
end;

procedure TRegMonitorThread.Execute;
begin
  InitThread;

  while not Terminated do
  begin
    if WaitForSingleObject(FEvent, INFINITE) = WAIT_OBJECT_0 then
    begin
      if Terminated then // <- add this 2 lines
        Exit;
      ...
    end;
  end;
end;