我要做一个托盘程序。可是每次我做完（在保存之前）一切都正常：可以将窗口最小化到托盘区，也可以点击托盘图标重新显示窗口。可是在我保存之后（其它任何操作都不做），再运行就不行了－－点击托盘图标却不能恢复窗口。为什么？
程序代码如下：
 Option Explicit
 Const MAX_TOOLTIP As Integer = 64
 Const NIF_ICON = &H2                          '删除图标
 Const NIF_MESSAGE = &H1
 Const NIF_TIP = &H4
 Const NIM_ADD = &H0                          '添加图标到任务栏提示区
 Const NIM_DELETE = &H2
 Const WM_MOUSEMOVE = &H200
 Const WM_LBUTTONDOWN = &H201
 Const WM_LBUTTONUP = &H202
 Const WM_LBUTTONDBLCLK = &H203
 Const WM_RBUTTONDOWN = &H204
 Const WM_RBUTTONUP = &H205
 Const WM_RBUTTONDBLCLK = &H206
 Const SW_RESTORE = 9
 Const SW_HIDE = 0
Const EM_UNDO = &HC7
 Private Type NOTIFYICONDATA
    cbSize           As Long
    hwnd             As Long
    uID              As Long
    uFlags           As Long
    uCallbackMessage As Long
    hIcon            As Long
    szTip            As String * MAX_TOOLTIP
End Type
Private Declare Function ShowWindow Lib "user32" (ByVal hwnd As Long, ByVal nCmdShow As Long) As Long
Private Declare Function Shell_NotifyIcon Lib "shell32.dll" Alias "Shell_NotifyIconA" (ByVal dwMessage As Long, lpData As NOTIFYICONDATA) As Long
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Any) As Long
Private Declare Function OSWinHelp% Lib "user32" Alias "WinHelpA" (ByVal hwnd&, ByVal HelpFile$, ByVal wCommand%, dwData As Any)
Private nfIconData As NOTIFYICONDATA

Private Sub MDIForm_Load()
    Me.Left = GetSetting(App.Title, "Settings", "MainLeft", 1000)
    Me.Top = GetSetting(App.Title, "Settings", "MainTop", 1000)
    Me.Width = GetSetting(App.Title, "Settings", "MainWidth", 6500)
    Me.Height = GetSetting(App.Title, "Settings", "MainHeight", 6500)
    mnuEditTimeTable_Click
    AddIcon
End Sub

Private Sub AddIcon()
  nfIconData.hwnd = Me.hwnd
  nfIconData.uID = Me.Icon
  nfIconData.uFlags = NIF_ICON Or NIF_MESSAGE Or NIF_TIP
  nfIconData.uCallbackMessage = WM_MOUSEMOVE
  nfIconData.hIcon = Me.Icon.Handle
  nfIconData.szTip = "时间表" & vbNullChar
  nfIconData.cbSize = Len(nfIconData)
  Call Shell_NotifyIcon(NIM_ADD, nfIconData)
End Sub

Private Sub LoadNewDoc()
    Static lDocumentCount As Long
    Dim frmD As frmDocument
    lDocumentCount = lDocumentCount + 1
    Set frmD = New frmDocument
    frmD.Caption = "Document " & lDocumentCount
    frmD.Show
End Sub

Private Sub MDIForm_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
  Dim lMsg As Single
  lMsg = X / Screen.TwipsPerPixelX
  If lMsg = WM_RBUTTONUP Or lMsg = WM_LBUTTONUP Then Me.Visible = True
End Sub

Private Sub MDIForm_Unload(Cancel As Integer)
    If Me.WindowState <> vbMinimized Then
        SaveSetting App.Title, "Settings", "MainLeft", Me.Left
        SaveSetting App.Title, "Settings", "MainTop", Me.Top
        SaveSetting App.Title, "Settings", "MainWidth", Me.Width
        SaveSetting App.Title, "Settings", "MainHeight", Me.Height
    End If
    Call Shell_NotifyIcon(NIM_DELETE, nfIconData)
End Sub

Private Sub mnuEditTimeTable_Click()
    Dim f As New frmTimeTable
    f.Show
End Sub

Private Sub mnuHideWindow_Click()
    ShowWindow Me.hwnd, SW_HIDE
End Sub

Private Sub mnuShowWindow_Click()
    Me.Visible = True
End Sub

Private Sub tbToolBar_ButtonClick(ByVal Button As MSComCtlLib.Button)
    On Error Resume Next
    Select Case Button.Key
        Case "新建"
            LoadNewDoc
        Case "打开"
            mnuFileOpen_Click
        Case "保存"
            mnuFileSave_Click
    End Select
End Sub

Private Sub mnuHelpAbout_Click()
    frmAbout.Show vbModal, Me
End Sub

Private Sub mnuHelpContents_Click()
    Dim nRet As Integer


    '如果这个工程没有帮助文件，显示消息给用户
    '可以在“工程属性”对话框中为应用程序设置帮助文件
    If Len(App.HelpFile) = 0 Then
        MsgBox "无法显示帮助目录，该工程没有相关联的帮助。", vbInformation, Me.Caption
    Else
        On Error Resume Next
        nRet = OSWinHelp(Me.hwnd, App.HelpFile, 3, 0)
        If Err Then
            MsgBox Err.Description
        End If
    End If

End Sub

Private Sub mnuWindowNewWindow_Click()
    LoadNewDoc
End Sub

Private Sub mnuToolsOptions_Click()
    frmOptions.Show vbModal, Me
End Sub

Private Sub mnuFileExit_Click()
    '卸载窗体
    Unload Me

End Sub

Private Sub mnuFileSaveAll_Click()
    '应做:添加 'mnuFileSaveAll_Click' 代码。
    MsgBox "添加 'mnuFileSaveAll_Click' 代码。"
End Sub

Private Sub mnuFileSaveAs_Click()
    Dim sFile As String
   
    If ActiveForm Is Nothing Then Exit Sub
    With dlgCommonDialog
        .DialogTitle = "另存为"
        .CancelError = False
        'ToDo: 设置 common dialog 控件的标志和属性
        .Filter = "所有文件 (*.*)|*.*"
        .ShowSave
        If Len(.FileName) = 0 Then
            Exit Sub
        End If
        sFile = .FileName
    End With
    ActiveForm.Caption = sFile
    ActiveForm.rtfText.SaveFile sFile

End Sub

Private Sub mnuFileSave_Click()
    Dim sFile As String
    If Left$(ActiveForm.Caption, 8) = "Document" Then
        With dlgCommonDialog
            .DialogTitle = "保存"
            .CancelError = False
            'ToDo: 设置 common dialog 控件的标志和属性
            .Filter = "所有文件 (*.*)|*.*"
            .ShowSave
            If Len(.FileName) = 0 Then
                Exit Sub
            End If
            sFile = .FileName
        End With
        ActiveForm.rtfText.SaveFile sFile
    Else
        sFile = ActiveForm.Caption
        ActiveForm.rtfText.SaveFile sFile
    End If

End Sub

Private Sub mnuFileClose_Click()
    '应做:添加 'mnuFileClose_Click' 代码。
    MsgBox "添加 'mnuFileClose_Click' 代码。"
End Sub

Private Sub mnuFileOpen_Click()
    Dim sFile As String


    If ActiveForm Is Nothing Then LoadNewDoc
   

    With dlgCommonDialog
        .DialogTitle = "打开"
        .CancelError = False
        'ToDo: 设置 common dialog 控件的标志和属性
        .Filter = "所有文件 (*.*)|*.*"
        .ShowOpen
        If Len(.FileName) = 0 Then
            Exit Sub
        End If
        sFile = .FileName
    End With
    ActiveForm.rtfText.LoadFile sFile
    ActiveForm.Caption = sFile

End Sub

Private Sub mnuFileNew_Click()
    LoadNewDoc
End Sub