如果我从主线程创建(挂起)线程,如下：
with TMyThread.Create(True) do
begin
OnTerminate := ThreadTerminated;
FreeOnTerminate := False;
Start;
end;
一旦完成,我该如何释放该实例？ (即执行过程已完成执行 – 假设我已捕获异常).
这个Proper way of destroying a tthread object链接显示了一种方法(通过PostMessage程序),它工作正常并且有意义.但是,如果我创建线程并且没有表单的句柄或者我可以调用PostMessage过程的东西,该怎么办？例如,我在直接从TObject下降的类中创建线程？
TMyClass = class
public
procedure DoSomething;
end;
TMyClass.DoSomething;
begin
with TMyThread.Create(True) do
begin
OnTerminate := ThreadTerminated;
FreeOnTerminate := False;
Start;
end;
end;
所以,我想,如何在不访问表单句柄的情况下释放一个线程？
谢谢
解决方法
显然,某处必须有对实例化线程的引用.但我可以提出你的愿望：你想要一个永远不做的解决方案.
我建议你通过一个单独的ThreadController类来管理线程的存在：
unit Unit2;
interface
uses
Classes,SysUtils,Forms,Windows,Messages;
type
TMyThreadProgressEvent = procedure(Value: Integer;
Proceed: Boolean) of object;
procedure RunMyThread(StartValue: Integer; OnProgress: TMyThreadProgressEvent);
implementation
type
TMyThread = class(TThread)
private
FException: Exception;
FOnProgress: TMyThreadProgressEvent;
FProceed: Boolean;
FValue: Integer;
procedure DoProgress;
procedure HandleException;
procedure ShowException;
protected
procedure Execute; override;
end;
TMyThreadController = class(TObject)
private
FThreads: TList;
procedure StartThread(StartValue: Integer;
OnProgress: TMyThreadProgressEvent);
procedure ThreadTerminate(Sender: TObject);
public
constructor Create;
destructor Destroy; override;
end;
var
FMyThreadController: TMyThreadController;
function MyThreadController: TMyThreadController;
begin
if not Assigned(FMyThreadController) then
FMyThreadController := TMyThreadController.Create;
Result := FMyThreadController
end;
procedure RunMyThread(StartValue: Integer; OnProgress: TMyThreadProgressEvent);
begin
MyThreadController.StartThread(StartValue,OnProgress);
end;
{ TMyThreadController }
constructor TMyThreadController.Create;
begin
inherited;
FThreads := TList.Create;
end;
destructor TMyThreadController.Destroy;
var
Thread: TThread;
begin
while FThreads.Count > 0 do
begin
Thread := FThreads[0]; //Save reference because Terminate indirectly
//extracts the list entry in OnTerminate!
Thread.Terminate; //Indirectly decreases FThreads.Count
Thread.Free;
end;
FThreads.Free;
inherited Destroy;
end;
procedure TMyThreadController.StartThread(StartValue: Integer;
OnProgress: TMyThreadProgressEvent);
var
Thread: TMyThread;
begin
Thread := TMyThread.Create(True);
FThreads.Add(Thread); //Add to list before a call to Resume because once
//resumed,the thread might be gone already!
Thread.FValue := StartValue;
Thread.FOnProgress := OnProgress;
Thread.OnTerminate := ThreadTerminate;
Thread.Resume;
end;
procedure TMyThreadController.ThreadTerminate(Sender: TObject);
begin
FThreads.Extract(Sender);
end;
{ TMyThread }
procedure TMyThread.DoProgress;
begin
if (not Application.Terminated) and Assigned(FOnProgress) then
FOnProgress(FValue,FProceed);
end;
procedure TMyThread.Execute;
begin
try
FProceed := True;
while (not Terminated) and (not Application.Terminated) and FProceed and
(FValue < 20) do
begin
Synchronize(DoProgress);
if not FProceed then
Break;
Inc(FValue);
Sleep(2000);
end;
//In case of normal execution ending,the thread may free itself. Otherwise,//the thread controller object frees the thread.
if not Terminated then
FreeOnTerminate := True;
except
HandleException;
end;
end;
procedure TMyThread.HandleException;
begin
FException := Exception(ExceptObject);
try
if not (FException is EAbort) then
Synchronize(ShowException);
finally
FException := nil;
end;
end;
procedure TMyThread.ShowException;
begin
if GetCapture <> 0 then
SendMessage(GetCapture,WM_CANCELMODE,0);
if (FException is Exception) and (not Application.Terminated) then
Application.ShowException(FException)
else
SysUtils.ShowException(FException,nil);
end;
initialization
finalization
FreeAndNil(FMyThreadController);
end.
要运行此示例线程,以2秒的间隔从5到19计数,并提供反馈和提前终止的机会,请从主线程调用：
type
TForm1 = class(TForm)
Button1: TButton;
procedure Button1Click(Sender: TObject);
private
procedure MyThreadProgress(Value: Integer; Proceed: Boolean);
end;
...
procedure TForm1.Button1Click(Sender: TObject);
begin
RunMyThread(5,MyThreadProgress);
end;
procedure TForm1.MyThreadProgress(Value: Integer; Proceed: Boolean);
begin
Caption := IntToStr(Value);
end;
该线程自动终止线程或应用程序的终止.
也许这个单位对你的情况有点矫枉过正,因为它能够处理多个线程(相同类型),但我认为它回答了你的问题.根据自己的喜好调整.
这个答案的部分来源：NLDelphi.com.