Allen 2011-06-03 10:26:17 11694 0 0 0 0
 
在Delphi中,通常可以用以下三种方法来实现程序的延时,即TTtimer控件,Sleep函数,GetTickCount函数。但是其精度是各不相同的。
一、三种方法的简单介绍
 
1)TTtimer控件
 
  TTtimer控件的实质是调用Windows API定时函数SetTimer和KillTimer来实现的,并简化了对WM_TIMER 消息的处理过程。通过设置OnTimer事件和Interval属性,我们可以很方便的产生一些简单的定时事件。
 
2)Sleep函数
 
  Sleep函数用来使程序的执行延时给定的时间值。Sleep的调用形式为Sleep(milliseconds),暂停当前的进程milliseconds毫秒。Sleep的实现方法其实也是调用Windows API的Sleep函数。例如:
 
sleep(1000); //延迟1000毫秒
 
Sleep会引起程序停滞,如果你延迟的时间较长的话,你的程序将不能够响应延时期间的发生的其他消息,所以程序看起来好像暂时死机。
 
3)GetTickCount函数
 
  在主程序中延时,为了达到延时和响应消息这两个目的,GetTickCount()构成的循环就是一种广为流传的方法。例如:
 
procedure Delay(MSecs: Longint);
//延时函数,MSecs单位为毫秒(千分之1秒)
var
FirstTickCount, Now: Longint;
begin
FirstTickCount := GetTickCount();
repeat
Application.ProcessMessages;
Now := GetTickCount();
until (Now - FirstTickCount >= MSecs) or (Now < FirstTickCount);
end;
 
二、高精度的微妙级性能计数器(high-resolution performance counter)介绍
 

###############################################################################################################################################################################################################################################################

 
1)计数器的Delphi源代码
 
{
A high-precision counter/timer. Retrieves time differences
downto microsec.
Quick Reference:
THPCounter inherits from TComponent.
 
Key-Methods:
Start: Starts the counter. Place this call just before the
code you want to measure.
 
Read: Reads the counter as a string. Place this call just
after the code you want to measure.
 
ReadInt: Reads the counter as an Int64. Place this call just
after the code you want to measure.
--------------------------------------------------------------------------------
}
unit HPCounter;
 
interface
 
uses
SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
Forms, Dialogs, StdCtrls, ExtCtrls;
 
type
TInt64 = TLargeInteger;
THPCounter = class(TComponent)
private
Frequency: TLargeInteger;
lpPerformanceCount1: TLargeInteger;
lpPerformanceCount2: TLargeInteger;
fAbout: string;
procedure SetAbout(Value: string);
{ Private declarations }
public
constructor Create(AOwner: TComponent); override;
destructor Destroy; override;
procedure Start;
function Read: string;
function ReadInt: TLargeInteger;
{ Private declarations }
published
property About: string read fAbout write SetAbout;
{ Published declarations }
end;
 
 
procedure Register;
 
implementation
 
procedure Register;
begin
RegisterComponents('MAs Prod.', [THPCounter]);
end;
 
constructor THPCounter.Create(AOwner: TComponent);
begin
inherited Create(AOwner);
fAbout:= 'Version 1.1, 2000® Mats Asplund, EMail: [email protected], Site: http://go.to/masdp';
end;
 
destructor THPCounter.Destroy;
begin
inherited Destroy;
end;
 
function THPCounter.Read: string;
begin
QueryPerformanceCounter(TInt64((@lpPerformanceCount2)^));
QueryPerformanceFrequency(TInt64((@Frequency)^));
Result:=IntToStr(Round(1000000 * (lpPerformanceCount2 -
lpPerformanceCount1) / Frequency));
end;
 
function THPCounter.ReadInt: TLargeInteger;
begin
QueryPerformanceCounter(TInt64((@lpPerformanceCount2)^));
QueryPerformanceFrequency(TInt64((@Frequency)^));
Result:=Round(1000000 * (lpPerformanceCount2 -
lpPerformanceCount1) / Frequency);
end;
 
procedure THPCounter.SetAbout(Value: string);
begin
Exit;
end;
 
procedure THPCounter.Start;
begin
QueryPerformanceCounter(TInt64((@lpPerformanceCount1)^));
end;
 
end.
 
2)使用方法:
unit Unit1;
 
interface
 
uses
Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
HPCounter, StdCtrls;
 
type
TForm1 = class(TForm)
Button1: TButton;
Edit1: TEdit;
Label1: TLabel;
Label2: TLabel;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;
 
var
Form1: TForm1;
 
implementation
 
{$R *.DFM}
 
procedure TForm1.Button1Click(Sender: TObject);
begin
Edit1.Text:= '';
Application.ProcessMessages;
with THPCounter.Create(Self) do
begin
Start;
// Place code to measure here
Sleep(1000);
// Place code to measure here
Edit1.Text:=Read;
Free;
end;
end;
 
end.
 
二、三种方法的精度比较
 
  为了比较,采用以上3种方法,分别设置延时时间为1ms、2ms、5ms、10ms、20ms、50ms、100ms、200ms、500ms、1000ms,循环次数为5次,得到实际的延时时间。
 
1)TTtimer控件
 
实际延时时间(ms)
1ms: 8.012 21.551 6.875 21.647 9.809
2ms: 9.957 20.675 14.671 11.903 20.551
5ms: 9.952 20.605 9.924 20.705 12.682
10ms:14.852 9.96 21.547 9.82 20.634
20ms:27.512 34.291 26.427 31.244 30.398
50ms:61.196 61.307 64.027 62.048 63.059
100ms:102.495 108.408 112.318 110.322 102.531
200ms:193.955 202.135 207.016 205.082 202.194
500ms:496.659 500.534 503.398 495.551 500.394
1000ms:999.699 1003.576 993.698 1004.443 995.625
 
2)Sleep函数
 
1ms: 1.895 1.895 1.896 1.897 1.898
2ms: 2.868 2.874 2.852 2.872 2.869
5ms: 5.8 5.797 5.79 5.79 5.791
10ms:10.675 10.683 10.611 10.669 10.67
20ms:20.404 20.434 20.447 20.477 20.368
50ms:50.67 50.691 50.69 50.682 50.671
100ms:100.515 100.469 100.484 100.481 100.484
200ms:200.101 200.126 199.892 200.066 200.108
500ms:499.961 499.961 499.958 499.961 499.96
1000ms:1000.034 1000.04 1000.03 1000.018 1000.029
 
3)GetTickCount函数
 
1ms: 15.54 15.596 15.527 15.566 15.838
2ms: 15.561 15.563 15.603 15.477 15.571
5ms: 15.519 15.549 15.569 15.666 15.394
10ms:15.558 15.561 15.522 15.568 15.518
20ms:31.186 31.137 31.17 31.17 31.19
50ms:62.445 62.4 63.893 60.88 62.404
100ms:109.276 109.298 109.273 109.28 109.28
200ms:203.027 203.084 203.021 203.027 203.046
500ms:499.959 499.961 499.963 499.967 499.965
1000ms:1000.023 1000.022 1000.026 1000.029 1000.021
 
 
  可见,相对而言,Sleep的精度最高,尤其是在10ms以内的延时,只有sleep函数才能够做到。TTimer控件的定时精度最差,而且稳定性不好,波动很大。GetTickCount函数所能实现的最短延时为15ms左右,稳定性相对TTimer要好一些。
 
(来源:http://blog.csdn.net/listenwind/)

Tag: 编程 Delphi技巧 TTTBLOG
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