TimerCallback 委托
表示处理来自 Timer 的调用的方法。
**命名空间:**System.Threading
**程序集:**mscorlib（在 mscorlib.dll 中）
语法
声明
<ComVisibleAttribute(True)> _
Public Delegate Sub TimerCallback ( _
state As Object _
)
用法
Dim instance As New TimerCallback(AddressOf HandlerMethod)
[ComVisibleAttribute(true)]
public delegate void TimerCallback (
Object state
)
[ComVisibleAttribute(true)]
public delegate void TimerCallback (
Object^ state
)
/** @delegate */
/** @attribute ComVisibleAttribute(true) */
public delegate void TimerCallback (
Object state
)
JScript 支持使用委托，但不支持进行新的声明。
参数
- state
一个对象（包含与该委托所调用的方法相关的特定于应用程序的信息）或为 空引用（在 Visual Basic 中为 Nothing）。
备注
使用 TimerCallback 委托指定由 Timer 调用的方法。此方法不在创建计时器的线程中执行，而是在系统提供的一个单独线程池线程中执行。在启动时间结束之后，TimerCallback 委托将调用一次该方法，并继续在每个计时器间隔调用一次该方法直到调用 Dispose 方法（或者以间隔值 Infinite 调用 Timer.Change 方法）为止。
计时器委托在构造计时器时指定，并且不能更改。Timer 的启动时间在 Timer 构造函数的 dueTime 参数中传递，时间周期在 period 参数中传递。有关演示如何创建和使用 TimerCallback 委托的示例，请参见 System.Threading.Timer。
示例
下面的代码示例说明如何创建用于 Timer 类的委托。
Imports Microsoft.VisualBasic
Imports System
Imports System.Threading
Public Class TimerExample
<MTAThread> _
Shared Sub Main()
Dim autoEvent As New AutoResetEvent(False)
Dim statusChecker As New StatusChecker(10)
' Create the delegate that invokes methods for the timer.
Dim timerDelegate As TimerCallback = _
AddressOf statusChecker.CheckStatus
' Create a timer that signals the delegate to invoke
' CheckStatus after one second, and every 1/4 second
' thereafter.
Console.WriteLine("{0} Creating timer." & vbCrLf, _
DateTime.Now.ToString("h:mm:ss.fff"))
Dim stateTimer As Timer = _
New Timer(timerDelegate, autoEvent, 1000, 250)
' When autoEvent signals, change the period to every
' 1/2 second.
autoEvent.WaitOne(5000, False)
stateTimer.Change(0, 500)
Console.WriteLine(vbCrLf & "Changing period." & vbCrLf)
' When autoEvent signals the second time, dispose of
' the timer.
autoEvent.WaitOne(5000, False)
stateTimer.Dispose()
Console.WriteLine(vbCrLf & "Destroying timer.")
End Sub
End Class
Public Class StatusChecker
Dim invokeCount, maxCount As Integer
Sub New(count As Integer)
invokeCount = 0
maxCount = count
End Sub
' This method is called by the timer delegate.
Sub CheckStatus(stateInfo As Object)
Dim autoEvent As AutoResetEvent = _
DirectCast(stateInfo, AutoResetEvent)
invokeCount += 1
Console.WriteLine("{0} Checking status {1,2}.", _
DateTime.Now.ToString("h:mm:ss.fff"), _
invokeCount.ToString())
If invokeCount = maxCount Then
' Reset the counter and signal to stop the timer.
invokeCount = 0
autoEvent.Set()
End If
End Sub
End Class
using System;
using System.Threading;
class TimerExample
{
static void Main()
{
AutoResetEvent autoEvent = new AutoResetEvent(false);
StatusChecker statusChecker = new StatusChecker(10);
// Create the delegate that invokes methods for the timer.
TimerCallback timerDelegate =
new TimerCallback(statusChecker.CheckStatus);
// Create a timer that signals the delegate to invoke
// CheckStatus after one second, and every 1/4 second
// thereafter.
Console.WriteLine("{0} Creating timer.\n",
DateTime.Now.ToString("h:mm:ss.fff"));
Timer stateTimer =
new Timer(timerDelegate, autoEvent, 1000, 250);
// When autoEvent signals, change the period to every
// 1/2 second.
autoEvent.WaitOne(5000, false);
stateTimer.Change(0, 500);
Console.WriteLine("\nChanging period.\n");
// When autoEvent signals the second time, dispose of
// the timer.
autoEvent.WaitOne(5000, false);
stateTimer.Dispose();
Console.WriteLine("\nDestroying timer.");
}
}
class StatusChecker
{
int invokeCount, maxCount;
public StatusChecker(int count)
{
invokeCount = 0;
maxCount = count;
}
// This method is called by the timer delegate.
public void CheckStatus(Object stateInfo)
{
AutoResetEvent autoEvent = (AutoResetEvent)stateInfo;
Console.WriteLine("{0} Checking status {1,2}.",
DateTime.Now.ToString("h:mm:ss.fff"),
(++invokeCount).ToString());
if(invokeCount == maxCount)
{
// Reset the counter and signal Main.
invokeCount = 0;
autoEvent.Set();
}
}
}
using namespace System;
using namespace System::Threading;
ref class StatusChecker
{
private:
int invokeCount;
int maxCount;
public:
StatusChecker( int count )
: invokeCount( 0 ), maxCount( count )
{}
// This method is called by the timer delegate.
void CheckStatus( Object^ stateInfo )
{
AutoResetEvent^ autoEvent = dynamic_cast<AutoResetEvent^>(stateInfo);
Console::WriteLine( "{0} Checking status {1,2}.", DateTime::Now.ToString( "h:mm:ss.fff" ), (++invokeCount).ToString() );
if ( invokeCount == maxCount )
{
// Reset the counter and signal main.
invokeCount = 0;
autoEvent->Set();
}
}
};
int main()
{
AutoResetEvent^ autoEvent = gcnew AutoResetEvent( false );
StatusChecker^ statusChecker = gcnew StatusChecker( 10 );
// Create the delegate that invokes methods for the timer.
TimerCallback^ timerDelegate = gcnew TimerCallback( statusChecker, &StatusChecker::CheckStatus );
// Create a timer that signals the delegate to invoke CheckStatus
// after one second, and every 1/4 second thereafter.
Console::WriteLine( "{0} Creating timer.\n", DateTime::Now.ToString( "h:mm:ss.fff" ) );
Timer^ stateTimer = gcnew Timer( timerDelegate,autoEvent,1000,250 );
// When autoEvent signals, change the period to every 1/2 second.
autoEvent->WaitOne( 5000, false );
stateTimer->Change( 0, 500 );
Console::WriteLine( "\nChanging period.\n" );
// When autoEvent signals the second time, dispose of the timer.
autoEvent->WaitOne( 5000, false );
stateTimer->~Timer();
Console::WriteLine( "\nDestroying timer." );
}
import System.*;
import System.Threading.*;
import System.Threading.Thread;
class TimerExample
{
public static void main(String[] args)
{
AutoResetEvent autoEvent = new AutoResetEvent(false);
StatusChecker statusChecker = new StatusChecker(10);
// Create the delegate that invokes methods for the timer.
TimerCallback timerDelegate = new TimerCallback(
statusChecker.CheckStatus);
// Create a timer that signals the delegate to invoke
// CheckStatus after one second, and every 1/4 second
// thereafter.
Console.WriteLine("{0} Creating timer.\n",
System.DateTime.get_Now().ToString("h:mm:ss.fff"));
Timer stateTimer = new Timer(timerDelegate, autoEvent, 1000, 250);
// When autoEvent signals, change the period to every
// 1/2 second.
autoEvent.WaitOne(5000, false);
stateTimer.Change(0, 500);
Console.WriteLine("\nChanging period.\n");
// When autoEvent signals the second time, dispose of
// the timer.
autoEvent.WaitOne(5000, false);
stateTimer.Dispose();
Console.WriteLine("\nDestroying timer.");
} //main
} //TimerExample
class StatusChecker
{
private int invokeCount, maxCount;
public StatusChecker(int count)
{
invokeCount = 0;
maxCount = count;
} //StatusChecker
// This method is called by the timer delegate.
public void CheckStatus(Object stateInfo)
{
AutoResetEvent autoEvent = ((AutoResetEvent)(stateInfo));
Console.WriteLine("{0} Checking status {1,2}.",
System.DateTime.get_Now().ToString("h:mm:ss.fff"),
String.valueOf(++invokeCount));
if (invokeCount == maxCount) {
// Reset the counter and signal Main.
invokeCount = 0;
autoEvent.Set();
}
} //CheckStatus
} //StatusChecker
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0
.NET Compact Framework
受以下版本支持：2.0、1.0
请参见
参考
System.Threading 命名空间
Timer 类
ThreadPool 类