Delphi线程定时器

(*

自己编写的线程计时器，没有采用消息机制，很有效

Cobbler续写

不用 TTimer 的原因:

要说TTimer类的使用问题，先要说一下它响应用户定义的回调函数(OnTimer)的方法。
TTimer拥有一个HWnd类型的成员变量FWindowHandle，用于捕捉系统消息。
TTimer在Enable的情况下，每隔Interval时间，就抛一个系统消息WM_TIMER,FWindowHandle捕捉到这个消息后，
就会执行用户的回调函数，实现用户需要的功能。就是这个消息机制引发了下面两个问题：

问题1: 还不算严重，TTimer与系统共用一个消息队列，也就是说，在用户回调函数处理完之前，
所有的系统消息都处于阻塞状态，包括界面的更新的消息。
如果你的回调函数瞬间执行完毕那就一切看着还正常，如果你要执行一个复杂耗时的操作，
比如数据库查询什么的（万一遇到数据库联接不正常，等待20秒），
那你的界面就必死无疑，直到回调函数执行完。如果是后台系统还好，
要是给用户使用的就没法交待了。即使你在子线程里面使用也不会解决的。

问题2: 一般系统定义消息的优先级比用户定义消息的优先级要低。
在子线程中使用TTimer时，如果线程间通信也大量使用自定义消息，
并且用户定义自己的消息处理函数，那WM_TIMER经常就会被丢弃了，
计时器就彻底失效了。

摘抄自网络

*)

unit UntThreadTimer;

interface

uses
Windows, Classes,Winapi.Messages;

type
TTimerStatus = (TS_ENABLE, TS_CHANGEINTERVAL, TS_DISABLE, TS_SETONTIMER);
TThreadedTimer = class;
TTimerThread = class;
PTimerThread = ^TTimerThread;

TTimerThread = class(TThread)
OwnerTimer: TThreadedTimer;
Interval: DWord;
Enabled : Boolean;
Status : TTimerStatus;
constructor Create(CreateSuspended: Boolean);
destructor Destroy; override;
procedure Execute; override;
procedure DoTimer;
end;

TThreadedTimer = class(TComponent)
private
FHandle: THandle;
FEnabled: Boolean;
FInterval: DWord;
FOnTimer: TNotifyEvent;
FTimerThread: TTimerThread;
FThreadPriority: TThreadPriority;
protected
procedure UpdateTimer;
procedure SetEnabled(Value: Boolean);
procedure SetInterval(Value: DWord);
procedure SetOnTimer(Value: TNotifyEvent);
procedure Timer; dynamic;
public
constructor Create(AHandle: THandle; AOwner: TComponent);
destructor Destroy; override;
published
property Enabled: Boolean read FEnabled write SetEnabled default True;
property Interval: DWord read FInterval write SetInterval default 1000;
property OnTimer: TNotifyEvent read FOnTimer write SetOnTimer;
end;

implementation

procedure WakeupDownThrdproc(const evenFlag: Integer); stdcall;
begin

end;
{TTimerThread}
constructor TTimerThread.Create(CreateSuspended: Boolean);
begin
inherited Create(CreateSuspended);
Interval := 1000;
Enabled := False;
Status := TS_DISABLE;
end;

destructor TTimerThread.Destroy;
begin
inherited;
end;

procedure TTimerThread.Execute;
begin
inherited;
while not Terminated do
begin
//SleepEx(Interval, True);
if (not Terminated) and (Status = TS_ENABLE) then Synchronize(DoTimer);
if Status <> TS_ENABLE then
begin
case Status of
TS_CHANGEINTERVAL:
begin
Status := TS_ENABLE;
SleepEx(0,True);
end;
TS_DISABLE:
begin
Status := TS_ENABLE;
SleepEx(0, True);
if not Terminated then Suspend;
end;
TS_SETONTIMER:
begin
Status := TS_ENABLE;
end else
Status := TS_ENABLE;
end;
end;
SleepEx(Interval, True);
end;
end;

procedure TTimerThread.DoTimer;
begin
OwnerTimer.Timer;
end;
{TThreadedTimer}
constructor TThreadedTimer.Create(AHandle: THandle; AOwner: TComponent);
begin
inherited Create(AOwner);
FHandle := AHandle;
FInterval := 1000;
FThreadPriority := tpNormal;
FTimerThread := TTimerThread.Create(true);
FTimerThread.OwnerTimer := self;
end;

destructor TThreadedTimer.Destroy;
begin
inherited Destroy;
FTimerThread.Terminate;
QueueUserAPC(@WakeupDownThrdproc, FTimerThread.Handle, DWORD(FTimerThread));
FTimerThread.Free;
end;

procedure TThreadedTimer.UpdateTimer;
begin
if (FEnabled = False) then
begin
FTimerThread.OwnerTimer := Self;
FTimerThread.Interval := FInterval;
FTimerThread.Priority := FThreadPriority;
FTimerThread.Resume;
end;
if (FEnabled = True) then
begin
QueueUserAPC(@WakeupDownThrdproc, FTimerThread.Handle, DWORD(FTimerThread));
end;
end;

procedure TThreadedTimer.SetEnabled(Value: Boolean);
begin
if Value <> FEnabled then
begin
FEnabled := Value;
if Value then
begin
FTimerThread.Status := TS_ENABLE;
FTimerThread.Resume;
end
else
begin
FTimerThread.Status := TS_DISABLE;
QueueUserAPC(@WakeupDownThrdproc, FTimerThread.Handle, DWORD(FTimerThread));
end;
end;
end;

procedure TThreadedTimer.SetInterval(Value: DWord);
begin
if Value <> FInterval then
begin
if (not Enabled) then
begin
FInterval := Value;
FTimerThread.Interval := FInterval;
end
else
begin
FInterval := Value;
FTimerThread.Interval := FInterval;
FTimerThread.Status := TS_CHANGEINTERVAL;
QueueUserAPC(@WakeupDownThrdproc, FTimerThread.Handle, DWORD(FTimerThread));
end;
end;
end;

procedure TThreadedTimer.SetOnTimer(Value: TNotifyEvent);
begin
FOnTimer := Value;
end;

procedure TThreadedTimer.Timer;
var
Msg: TMessage;
begin
Msg.Msg := WM_USER+100;
//if Assigned(FOnTimer) then FOnTimer(Self);
SendMessage(FHandle,msg.Msg,0,0);
end;

end.