我一直想知道有没有更好的方法，我应该写一些我的程序，特别是那些需要很长时间才能完成的程序。
我总是从主GUI线程运行所有的东西，我现在明白并认识到这是坏的，因为它会使应用程序无响应，Application.ProcessMessages在这里不会真的有帮助。
这使我觉得我需要使用TThreads进行冗长的操作，例如复制一个文件。这也让我想知道一些应用程序如何为您提供完全控制，例如允许您暂停，恢复和/或停止操作。
我在一个个人项目中有大约3个冗长的操作，我正在使用一个TProgressBar来显示一个对话框。虽然这样做有效，但我觉得可以做得更好。这些进度对话框可能会显示很长时间，您可能希望取消操作，稍后再完成该作业。
正如我所说，目前我运行的主要线程，我需要使用TThreads吗？我不知道如何或在哪里开始实施它们，因为我以前没有和他们一起工作。如果我需要线程，他们提供我需要的，如暂停，恢复，停止操作等？
基本上我正在寻找一种更好的处理和管理冗长的操作的方法。
解决方法
是的，这绝对是你需要一个线程来完成任务的情况。
一个例子如何暂停/恢复线程并取消线程。
进度通过PostMessage调用发送到主线程。
暂停/恢复和取消通过TSimpleEvent信号进行。
编辑：根据@mghie的评论，这里是一个更完整的例子：
unit WorkerThread;
interface
uses Windows,Classes,SyncObjs;
type
TWorkFunction = function: boolean of object;
TWorkerThread = Class(TThread)
private
FCancelFlag: TSimpleEvent;
FDoWorkFlag: TSimpleEvent;
FOwnerFormHandle: HWND;
FWorkFunc: TWorkFunction; // Function method to call
FCallbackMsg: integer; // PostMessage id
FProgress: integer;
procedure SetPaused(doPause: boolean);
function GetPaused: boolean;
procedure Execute; override;
public
Constructor Create(WindowHandle: HWND; callbackMsg: integer;
myWorkFunc: TWorkFunction);
Destructor Destroy; override;
function StartNewWork(newWorkFunc: TWorkFunction): boolean;
property Paused: boolean read GetPaused write SetPaused;
end;
implementation
constructor TWorkerThread.Create(WindowHandle: HWND; callbackMsg: integer;
myWorkFunc: TWorkFunction);
begin
inherited Create(false);
FOwnerFormHandle := WindowHandle;
FDoWorkFlag := TSimpleEvent.Create;
FCancelFlag := TSimpleEvent.Create;
FWorkFunc := myWorkFunc;
FCallbackMsg := callbackMsg;
Self.FreeOnTerminate := false; // Main thread controls for thread destruction
if Assigned(FWorkFunc) then
FDoWorkFlag.SetEvent; // Activate work at start
end;
destructor TWorkerThread.Destroy; // Call MyWorkerThread.Free to cancel the thread
begin
FDoWorkFlag.ResetEvent; // Stop ongoing work
FCancelFlag.SetEvent; // Set cancel flag
Waitfor; // Synchronize
FCancelFlag.Free;
FDoWorkFlag.Free;
inherited;
end;
procedure TWorkerThread.SetPaused(doPause: boolean);
begin
if doPause then
FDoWorkFlag.ResetEvent
else
FDoWorkFlag.SetEvent;
end;
function TWorkerThread.StartNewWork(newWorkFunc: TWorkFunction): boolean;
begin
Result := Self.Paused; // Must be paused !
if Result then
begin
FWorkFunc := newWorkFunc;
FProgress := 0; // Reset progress counter
if Assigned(FWorkFunc) then
FDoWorkFlag.SetEvent; // Start work
end;
end;
procedure TWorkerThread.Execute;
{- PostMessage LParam:
0 : Work in progress,progress counter in WParam
1 : Work is ready
2 : Thread is closing
}
var
readyFlag: boolean;
waitList: array [0 .. 1] of THandle;
begin
FProgress := 0;
waitList[0] := FDoWorkFlag.Handle;
waitList[1] := FCancelFlag.Handle;
while not Terminated do
begin
if (WaitForMultipleObjects(2,@waitList[0],false,INFINITE) <>
WAIT_OBJECT_0) then
break; // Terminate thread when FCancelFlag is signaled
// Do some work
readyFlag := FWorkFunc;
if readyFlag then // work is done,pause thread
Self.Paused := true;
Inc(FProgress);
// Inform main thread about progress
PostMessage(FOwnerFormHandle,FCallbackMsg,WPARAM(FProgress),LPARAM(readyFlag));
end;
PostMessage(FOwnerFormHandle,LPARAM(2)); // Closing thread
end;
function TWorkerThread.GetPaused: boolean;
begin
Result := (FDoWorkFlag.Waitfor(0) <> wrSignaled);
end;
end.
只需调用MyThread.Paused：= true来暂停，MyThread.Paused：= false来恢复线程操作。
要取消线程，请调用MyThread.Free。
要从线程接收已发布的消息，请参阅以下示例：
unit Unit1;
interface
uses
Winapi.Windows,Winapi.Messages,System.SysUtils,System.Variants,System.Classes,Vcl.Graphics,Vcl.Controls,Vcl.Forms,Vcl.Dialogs,Vcl.StdCtrls,WorkerThread;
const
WM_MyProgress = WM_USER + 0; // The unique message id
type
TForm1 = class(TForm)
Label1: TLabel;
btnStartTask: TButton;
btnPauseResume: TButton;
btnCancelTask: TButton;
Label2: TLabel;
procedure btnStartTaskClick(Sender: TObject);
procedure btnPauseResumeClick(Sender: TObject);
procedure btnCancelTaskClick(Sender: TObject);
private
{ Private declarations }
MyThread: TWorkerThread;
workLoopIx: integer;
function HeavyWork: boolean;
procedure OnMyProgressMsg(var Msg: TMessage); message WM_MyProgress;
public
{ Public declarations }
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
{ TForm1 }
const
cWorkLoopMax = 500;
function TForm1.HeavyWork: boolean; // True when ready
var
i,j: integer;
begin
j := 0;
for i := 0 to 10000000 do
Inc(j);
Inc(workLoopIx);
Result := (workLoopIx >= cWorkLoopMax);
end;
procedure TForm1.btnStartTaskClick(Sender: TObject);
begin
if not Assigned(MyThread) then
begin
workLoopIx := 0;
btnStartTask.Enabled := false;
btnPauseResume.Enabled := true;
btnCancelTask.Enabled := true;
MyThread := TWorkerThread.Create(Self.Handle,WM_MyProgress,HeavyWork);
end;
end;
procedure TForm1.btnPauseResumeClick(Sender: TObject);
begin
if Assigned(MyThread) then
MyThread.Paused := not MyThread.Paused;
end;
procedure TForm1.btnCancelTaskClick(Sender: TObject);
begin
if Assigned(MyThread) then
begin
FreeAndNil(MyThread);
btnStartTask.Enabled := true;
btnPauseResume.Enabled := false;
btnCancelTask.Enabled := false;
end;
end;
procedure TForm1.OnMyProgressMsg(var Msg: TMessage);
begin
Msg.Msg := 1;
case Msg.LParam of
0:
Label1.Caption := Format('%5.1f %%',[100.0 * Msg.WParam / cWorkLoopMax]);
1:
begin
Label1.Caption := 'Task done';
btnCancelTaskClick(Self);
end;
2:
Label1.Caption := 'Task terminated';
end;
end;
end.
形式：
object Form1: TForm1
Left = 0
Top = 0
Caption = 'Form1'
ClientHeight = 163
ClientWidth = 328
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -13
Font.Name = 'Tahoma'
Font.Style = []
OldCreateOrder = False
PixelsPerInch = 120
TextHeight = 16
object Label1: TLabel
Left = 79
Top = 18
Width = 51
Height = 16
Caption = 'Task idle'
end
object Label2: TLabel
Left = 32
Top = 18
Width = 41
Height = 16
Caption = 'Status:'
end
object btnStartTask: TButton
Left = 32
Top = 40
Width = 137
Height = 25
Caption = 'Start'
TabOrder = 0
OnClick = btnStartTaskClick
end
object btnPauseResume: TButton
Left = 32
Top = 71
Width = 137
Height = 25
Caption = 'Pause/Resume'
Enabled = False
TabOrder = 1
OnClick = btnPauseResumeClick
end
object btnCancelTask: TButton
Left = 32
Top = 102
Width = 137
Height = 25
Caption = 'Cancel'
Enabled = False
TabOrder = 2
OnClick = btnCancelTaskClick
end
end