最近常常遇到线程,线程的释放的问题让我一直拿捏不准。今天写了一个简单的线程,本来还从中学了点东西,但是最后遭遇到一个大问题,就是主线程要Destroy的时候,尝试释放线程就失效了,用FastMM以检测,线程对象、线程中手动申请的内存完全释放不了。但是,可以先调用Termiante,然后调用Close关闭掉主窗口,关掉程序就没有问题,于是,我目前只好做成尝试关掉主窗口前强制手动Termiante。
线程类代码unit UThread;interface
uses
Classes, Dialogs, Windows, SysUtils;type
TMyThread = class(TThread)
private
FMainHandle: THandle;
FNum: Integer;
FAnswer: Cardinal;
FTimeElapse: Cardinal;
FShowLst: TList;
procedure DoOnTerminate(Sender: TObject);
procedure DisplayAnswer;
protected
procedure Execute; override;
public
constructor create(Suspended: Boolean; Vol: Cardinal);
destructor destroy; override;
property Terminated;
property MainHandle: THandle read FMainHandle write FMainHandle;
end;implementation
uses
UMain;{ TMyThread }constructor TMyThread.create(Suspended: Boolean; Vol: Cardinal);
begin
FNum := Vol;
FreeOnTerminate := True;
OnTerminate := DoOnTerminate;
inherited Create(Suspended);
FShowLst := TList.Create;
end;destructor TMyThread.destroy;
begin
FreeAndNil(FShowLst);
inherited;
end;procedure TMyThread.DisplayAnswer;
begin
Form1.edt1.Text := IntToStr(FAnswer);
if Form1.pb1.Position < Form1.pb1.Max then
Form1.pb1.StepIt;
end;procedure TMyThread.DoOnTerminate(Sender: TObject);
begin
begin
MessageBox(Form1.Handle, PChar(Format('Total Time Elapse:%d', [FTimeElapse])),
'Info', 0);
Form1.pb1.Position := 1;
Form1.btn1.Enabled := True;
end;
end;procedure TMyThread.Execute;
var
i: Integer;
Start_TickCount, k: Cardinal;
begin
Start_TickCount := GetTickCount;
for i := 0 to FNum - 1 do
begin
k := Round(Abs(Sin(Sqrt(i))));
if Terminated then
Break;
FAnswer := FAnswer + k;
Synchronize(DisplayAnswer);
end;
FTimeElapse := GetTickCount - Start_TickCount;
inherited;
end;end.主线程代码unit UMain;interfaceuses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, UThread, ComCtrls, Buttons;type
TForm1 = class(TForm)
btnCreateSuspend: TButton;
edtDisplay: TEdit;
pb1: TProgressBar;
btnSuspend: TButton;
btnResume: TButton;
btnTerminate: TButton;
btnCheckThreadStatus: TButton;
btn6: TSpeedButton;
procedure btnCreateSuspendClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure btnSuspendClick(Sender: TObject);
procedure btnTerminateClick(Sender: TObject);
procedure btnResumeClick(Sender: TObject);
procedure btnCheckThreadStatusClick(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure btn7Click(Sender: TObject);
procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
private
{ Private declarations }
procedure TerminateThread;
public
{ Public declarations }
FThread: TMyThread;
end;var
Form1: TForm1;implementation{$R *.dfm}procedure TForm1.btnCreateSuspendClick(Sender: TObject);
var
Vol: Integer;
begin
Vol := 200000;
FThread := TMyThread.create(True, Vol);
pb1.Max := Vol;
TButton(Sender).Enabled := False;
end;procedure TForm1.FormCreate(Sender: TObject);
begin
pb1.Step := 1;
end;procedure TForm1.btnSuspendClick(Sender: TObject);
begin
if not FThread.Terminated then
begin
FThread.Suspended := not FThread.Suspended;
end;
end;procedure TForm1.btnTerminateClick(Sender: TObject);
begin
TerminateThread;
end;procedure TForm1.btnResumeClick(Sender: TObject);
begin
if Assigned(FThread) and (not FThread.Terminated) and (FThread.Suspended) then
FThread.Resume;
end;procedure TForm1.btnCheckThreadStatusClick(Sender: TObject);
var
sStatus: string;
begin
if not Assigned(FThread) then
begin
sStatus := 'Thread is nil!';
btn6.Caption := 'Thread Current Status: ' + sStatus;
Exit;
end; if FThread.Suspended then
begin
sStatus := 'Is Suspended: Yes ;';
end
else
sStatus := 'Is Suspended: No ;'; if FThread.Terminated then
begin
sStatus := sStatus + ' Is Terminated: Yes';
end
else
sStatus := sStatus + ' Is Terminated: No';
btn6.Caption := 'Thread Current Status: ' + sStatus;
end;procedure TForm1.FormDestroy(Sender: TObject);
begin
try
TerminateThread;
except
end;
end;procedure TForm1.TerminateThread;
begin
if Assigned(FThread) and (not FThread.Terminated) then
begin
if FThread.Suspended then
begin
FThread.Resume;
end;
FThread.Terminate;
FThread := nil;
end;
end;{没办法,强制Terminate线程才允许关闭窗口,有什么办法可以解决这个问题?}
procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
CanClose := (FThread = nil) or (FThread.Terminated = True);
if not CanClose then
MessageBox(Handle, 'Termiante the thread first!', ' Terminate thread', 0);
end;end.代码贴得比较多,但是其实很简单,我现在就是拿捏不准,在主线程Destroy的时候调用TerminateThread完全没有用,根本没有释放线程相关的资源,但是点击btnTerminate就可以正常的释放,调用的是相同的代码。最后,我发现,在主线程Destroy的时候,如果把线程类定义中的OnTerminate := DoOnTerminate;这一句屏蔽掉也正常,但是这屏蔽了正常的执行线程就有问题了,不能及时的刷新窗口,也许你会说在Execute中同步一个方法,但是我如果就想在OnTerminate中实现该怎样处理?或者说怎样通知线程在主线程要Destroy的时候就不要再刷新窗口了,我尝试在OnTerminate的赋值方法中调用类似
if not (csDestroying in Form1.ComponentState) then
//刷新UI
但是也没有收到相应的效果。
这个到底该怎么办呢?
线程类代码unit UThread;interface
uses
Classes, Dialogs, Windows, SysUtils;type
TMyThread = class(TThread)
private
FMainHandle: THandle;
FNum: Integer;
FAnswer: Cardinal;
FTimeElapse: Cardinal;
FShowLst: TList;
procedure DoOnTerminate(Sender: TObject);
procedure DisplayAnswer;
protected
procedure Execute; override;
public
constructor create(Suspended: Boolean; Vol: Cardinal);
destructor destroy; override;
property Terminated;
property MainHandle: THandle read FMainHandle write FMainHandle;
end;implementation
uses
UMain;{ TMyThread }constructor TMyThread.create(Suspended: Boolean; Vol: Cardinal);
begin
FNum := Vol;
FreeOnTerminate := True;
OnTerminate := DoOnTerminate;
inherited Create(Suspended);
FShowLst := TList.Create;
end;destructor TMyThread.destroy;
begin
FreeAndNil(FShowLst);
inherited;
end;procedure TMyThread.DisplayAnswer;
begin
Form1.edt1.Text := IntToStr(FAnswer);
if Form1.pb1.Position < Form1.pb1.Max then
Form1.pb1.StepIt;
end;procedure TMyThread.DoOnTerminate(Sender: TObject);
begin
begin
MessageBox(Form1.Handle, PChar(Format('Total Time Elapse:%d', [FTimeElapse])),
'Info', 0);
Form1.pb1.Position := 1;
Form1.btn1.Enabled := True;
end;
end;procedure TMyThread.Execute;
var
i: Integer;
Start_TickCount, k: Cardinal;
begin
Start_TickCount := GetTickCount;
for i := 0 to FNum - 1 do
begin
k := Round(Abs(Sin(Sqrt(i))));
if Terminated then
Break;
FAnswer := FAnswer + k;
Synchronize(DisplayAnswer);
end;
FTimeElapse := GetTickCount - Start_TickCount;
inherited;
end;end.主线程代码unit UMain;interfaceuses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, UThread, ComCtrls, Buttons;type
TForm1 = class(TForm)
btnCreateSuspend: TButton;
edtDisplay: TEdit;
pb1: TProgressBar;
btnSuspend: TButton;
btnResume: TButton;
btnTerminate: TButton;
btnCheckThreadStatus: TButton;
btn6: TSpeedButton;
procedure btnCreateSuspendClick(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure btnSuspendClick(Sender: TObject);
procedure btnTerminateClick(Sender: TObject);
procedure btnResumeClick(Sender: TObject);
procedure btnCheckThreadStatusClick(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure btn7Click(Sender: TObject);
procedure FormCloseQuery(Sender: TObject; var CanClose: Boolean);
private
{ Private declarations }
procedure TerminateThread;
public
{ Public declarations }
FThread: TMyThread;
end;var
Form1: TForm1;implementation{$R *.dfm}procedure TForm1.btnCreateSuspendClick(Sender: TObject);
var
Vol: Integer;
begin
Vol := 200000;
FThread := TMyThread.create(True, Vol);
pb1.Max := Vol;
TButton(Sender).Enabled := False;
end;procedure TForm1.FormCreate(Sender: TObject);
begin
pb1.Step := 1;
end;procedure TForm1.btnSuspendClick(Sender: TObject);
begin
if not FThread.Terminated then
begin
FThread.Suspended := not FThread.Suspended;
end;
end;procedure TForm1.btnTerminateClick(Sender: TObject);
begin
TerminateThread;
end;procedure TForm1.btnResumeClick(Sender: TObject);
begin
if Assigned(FThread) and (not FThread.Terminated) and (FThread.Suspended) then
FThread.Resume;
end;procedure TForm1.btnCheckThreadStatusClick(Sender: TObject);
var
sStatus: string;
begin
if not Assigned(FThread) then
begin
sStatus := 'Thread is nil!';
btn6.Caption := 'Thread Current Status: ' + sStatus;
Exit;
end; if FThread.Suspended then
begin
sStatus := 'Is Suspended: Yes ;';
end
else
sStatus := 'Is Suspended: No ;'; if FThread.Terminated then
begin
sStatus := sStatus + ' Is Terminated: Yes';
end
else
sStatus := sStatus + ' Is Terminated: No';
btn6.Caption := 'Thread Current Status: ' + sStatus;
end;procedure TForm1.FormDestroy(Sender: TObject);
begin
try
TerminateThread;
except
end;
end;procedure TForm1.TerminateThread;
begin
if Assigned(FThread) and (not FThread.Terminated) then
begin
if FThread.Suspended then
begin
FThread.Resume;
end;
FThread.Terminate;
FThread := nil;
end;
end;{没办法,强制Terminate线程才允许关闭窗口,有什么办法可以解决这个问题?}
procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
begin
CanClose := (FThread = nil) or (FThread.Terminated = True);
if not CanClose then
MessageBox(Handle, 'Termiante the thread first!', ' Terminate thread', 0);
end;end.代码贴得比较多,但是其实很简单,我现在就是拿捏不准,在主线程Destroy的时候调用TerminateThread完全没有用,根本没有释放线程相关的资源,但是点击btnTerminate就可以正常的释放,调用的是相同的代码。最后,我发现,在主线程Destroy的时候,如果把线程类定义中的OnTerminate := DoOnTerminate;这一句屏蔽掉也正常,但是这屏蔽了正常的执行线程就有问题了,不能及时的刷新窗口,也许你会说在Execute中同步一个方法,但是我如果就想在OnTerminate中实现该怎样处理?或者说怎样通知线程在主线程要Destroy的时候就不要再刷新窗口了,我尝试在OnTerminate的赋值方法中调用类似
if not (csDestroying in Form1.ComponentState) then
//刷新UI
但是也没有收到相应的效果。
这个到底该怎么办呢?
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我现在想知道的是,在上面的情况下,是否有其他的手段解决呢?
没必要弄的你那么麻烦,又是调用这个,又是调用那个的
一、创建的线程时候,设置FreeOnTerminate为True,把需要需要更新的主线程的代码放到OnTerminate的回调函数中。这种种情况下:1.在主线程未销毁的时候,确保线程已经在运行了,然后调用AThread.Terminate,就可以正常的释放,不过此时的AThread不是为nil的,为了安全起见,这里可以手动设置为nil 2.在主线程销毁的时候,就不能继续按照1的方法来释放,必须在调用Destroy之前,用1的方法释放。
二、创建线程的时候,设置FreeOnTermiante为False,这时候,OnTermiante就不要复制了,所有的需要访问主线程的部分可以放到多个方法中,然后用Synchronize同步就可以了,需要手动释放的部分就放到线程的Destroy中,然后在需要释放线程的时候,直接调用FreeAndNil(AThread)就可以了。如此看来还是第二种比较好,可以像释放普通对象一样释放。
看到一个帖子上说,使用TThread类的前提是FreeOnTerminate为True,这个说法也是不正确的,只能说,你设置了FreeOnTerminate为True,线程在最后会主动调用AThread.Free,但是也可以手动的调用FreeAndNil(AThread),不过这个前提是FreeOnTerminate为False的,否则,线程最后调用了Free,再调用FreeAndNil肯定会报错的。
procedure TMyThread.DisplayAnswer;
begin
if (nil <> Form1) then
begin
Form1.edt1.Text := IntToStr(FAnswer);
if Form1.pb1.Position < Form1.pb1.Max then
Form1.pb1.StepIt;
end;
end;procedure TMyThread.DoOnTerminate(Sender: TObject);
begin
if (nil <> Form1) then
begin
MessageBox(Form1.Handle, PChar(Format('Total Time Elapse:%d', [FTimeElapse])),
'Info', 0);
Form1.pb1.Position := 1;
Form1.btn1.Enabled := True;
end;
end;procedure TForm1.FormDestroy(Sender: TObject);
begin
Form1 := nil;
TerminateThread;
end;