VB 纯代码实现Timer控件的功能

本博客有一篇类似的文章《VB 中运用 TimeSetEvent 代替 Timer 控件》与这篇不同。
本篇展示了另外两种方法，具体如下文所示。

方法1：
　　用这个类可以替代VB自带的Timer控件，这样就不用在无窗体的项目中仅为了使用Timer而多加一个窗体了。我一般用在ActiveX exe中用来分离系统控制权，用Timer的好处是避免控制权死锁，这样也就模拟出了多线程(实际上是多进程)，能给用户更好的体验。代码如下：
标准模块(mTimer.bas)

Option Explicit
Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByRef Destination As Any, ByRef Source As Any, ByVal Length As Long)
Public TimerColl As New VBA.Collection

Public Sub TimeProc(ByVal hWnd As Long, ByVal uMsg As Long, ByVal idEvent As Long, ByVal dwTime As Long)
Dim Timer As Timer, lpTimer As Long
lpTimer = TimerColl("ID:" & idEvent)
CopyMemory Timer, lpTimer, 4&
Timer.PulseTimer
CopyMemory Timer, 0&, 4&
End Sub

类模块(Timer.bas)

Option Explicit

Private Declare Function SetTimer Lib "user32" (ByVal hWnd As Long, ByVal nIDEvent As Long, ByVal uElapse As Long, ByVal lpTimerFunc As Long) As Long
Private Declare Function KillTimer Lib "user32" (ByVal hWnd As Long, ByVal nIDEvent As Long) As Long

Private m_TimerID As Long
Private m_Interval As Long
Private m_Enabled As Boolean

Public Tag As Variant
Public Event Timer()

Public Property Get Interval() As Long
Interval = m_Interval
End Property

Public Property Let Interval(ByVal Value As Long)
m_Interval = Value
Enabled = m_Enabled
End Property

Public Property Get Enabled() As Boolean
Interval = m_Enabled
End Property

Public Property Let Enabled(ByVal Value As Boolean)
If Value Then
m_Enabled = StartTimer
Else
Call StopTimer
End If
End Property

Private Function StartTimer() As Boolean
If m_TimerID = 0 Then
If m_Interval > 0 Then
m_TimerID = SetTimer(0, 0, m_Interval, AddressOf TimeProc)
If m_TimerID <> 0 Then
TimerColl.Add ObjPtr(Me), "ID:" & m_TimerID
StartTimer = True
End If
Else
m_Enabled = True
End If
End If
End Function

Friend Sub PulseTimer()
RaiseEvent Timer
End Sub

Private Sub StopTimer()
If m_TimerID <> 0 Then
KillTimer 0, m_TimerID
TimerColl.Remove "ID:" & m_TimerID
m_TimerID = 0
m_Enabled = False
End If
End Sub

Private Sub Class_Terminate()
Call StopTimer
End Sub

使用方法：
Private WithEvents Timer1 As Timer
Private Sub Form_Load()
Set Timer1 = New TimerLib.Timer
Timer1.Interval = 1000
Timer1.Enabled = True
End Sub
Private Sub Timer1_Timer()
Debug.Print Now
End Sub

方法2：
用SetTimer函数定义一个ID,并标志一个触发时间(以MS为单位)和回调函数地址.
当指定的触发时间到了,系统就会调用那个指定的回调函数,并以你在SetTimer时定义的ID为参数,这样就可以区别多个定时器了.
当不需要使用某个定时器时,就使用KillTimer函数把指定ID的定时器干掉就可以了.
窗体代码：

Option Explicit

Const GWL_WNDPROC = (-4)

Private Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" (ByVal hWnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long

Private Declare Function SetTimer Lib "user32" (ByVal hWnd As Long, ByVal nIDEvent As Long, ByVal uElapse As Long, ByVal lpTimerFunc As Long) As Long
Private Declare Function KillTimer Lib "user32" (ByVal hWnd As Long, ByVal nIDEvent As Long) As Long

Private Sub Form_Load()
glngFuncAdd = SetWindowLong(hWnd, GWL_WNDPROC, AddressOf WndProc_TimerTest)
Call SetTimer(hWnd, TIMERID, 500, 0&)
End Sub

Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
If glngFuncAdd > 0 Then Call SetWindowLong(hWnd, GWL_WNDPROC, glngFuncAdd)
Call KillTimer(hWnd, TIMERID)
End Sub

模块代码：

Option Explicit

Const WM_TIMER = &H113

Public Const TIMERID = &H100 '自定义Timer的ID号

Private Declare Function CallWindowProc Lib "user32" Alias "CallWindowProcA" (ByVal lpPrevWndFunc As Long, ByVal hWnd As Long, ByVal Msg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long

Public glngFuncAdd As Long

Public Function WndProc_TimerTest(ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
If wMsg = WM_TIMER Then
If wParam = TIMERID Then
Debug.Print Timer
End If
End If

WndProc_TimerTest = CallWindowProc(glngFuncAdd, hWnd, wMsg, wParam, lParam)
End Function