frmmain.frm

VB开发OPC Client的教程和源码

                ' from an OPC Server have a starting index of 0
                For b = 0 To UBound(ItemValue)
                    itmX.SubItems(1) = itmX.SubItems(1) + Str(ItemValue(b)) + ", "
                Next b
            End If
                
            ' Get the item quailty condition directly from the OPC server
            Quality = OPCItemData.GetItemQuality(OPCItemDirect)
            
            ' The "Data Access Automation Interface Standard" specification
            ' doesn't directly tell you the contents of the quailty field but
            ' in general if the field contains the value 192 of 0xC0 Hex the
            ' data can be considered OK.
            If Quality And &HC0 Then
               itmX.SubItems(2) = "Good" ' if quailty is 192 then OK
            Else
               itmX.SubItems(2) = "Bad " + Str(Quality) ' If the not 192 show Bad and value.
            End If
    Next i
              
SkipListUpdate:

End Sub


' Like the MouseUp handler for the TreeView, this sub handles all
' user interaction with the ListView control.  If the user right clicks
' in the lsit view they will be presented with a context popup. If the
' user has an item selected when the right button is pressed they will
' be able to add a new item, make the selected item active or inactive,
' write to the item, or delete it.  If the user right click without selecting
' an item they will be able to add a new item.
'
Private Sub lvListView_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
    ' As I mentioned above I use the enabled state of the tree view
    ' to determine if user input is allowed in the ListView.  I do
    ' this since at each point a new form will be displayed I disable
    ' the TreeView control.  This causes the treeview to become greyed out
    ' and prevents the user from invloking a popup from the tree view.
    ' If I uses the .enabled property of the ListView the whole view
    ' gets greyed out and looks pretty bad.  By monitoring the
    ' .enabled state of the treeview I can disble the listview input while
    ' keeping the display clear.
    If tvTreeView.Enabled = True Then
        ' First we need to make sure that a group is selected in the
        ' treeview control.
        If Not tvTreeView.SelectedItem Is Nothing Then
            If InStr(tvTreeView.SelectedItem.Key, "Group") Then
                ' A group is selected in the treeview if the right button
                ' is pressed show a popup.
                If (Button = vbRightButton) Then
                    ' The "New Item" selection is always allowed.
                    mnuListViewNewItem.Visible = True
                    mnuListViewNewItem.Enabled = True
                    
                    ' Is an item selected in the ListView
                    If Not lvListView.SelectedItem Is Nothing Then
                       Dim SelectedItem As ListItem
                       ' We use the hit test here to make sure the user
                       ' is directly on a specific item.
                       Set SelectedItem = lvListView.HitTest(X, Y)
                       If Not SelectedItem Is Nothing Then
                            Dim OPCGroupItemsCls As Collection
                            Set OPCGroupItemsCls = Module1.SelectedOPCGroup.GetOPCGroupItemsCollection
                            ' Set the SelectedOPCItem pointer
                            Set Module1.SelectedOPCItem = OPCGroupItemsCls.Item(Mid(SelectedItem.Key, InStr(SelectedItem.Key, " ")))
                            ' Display all Item options on the popup.
                            mnuListViewSetActive.Visible = True
                            mnuListViewSetActive.Enabled = True
                            mnuListViewSetInactive.Visible = True
                            mnuListViewSetInactive.Enabled = True
                            mnuListViewWriteValue.Visible = True
                            mnuListViewWriteValue.Enabled = True
                            mnuListViewDelete.Visible = True
                            mnuListViewDelete.Enabled = True
                        Else
                            ' The user is not directly on an item so show only
                            ' the "Add Item" selection.
                            mnuListViewSetActive.Visible = False
                            mnuListViewSetActive.Enabled = False
                            mnuListViewSetInactive.Visible = False
                            mnuListViewSetInactive.Enabled = False
                            mnuListViewWriteValue.Visible = False
                            mnuListViewWriteValue.Enabled = False
                            mnuListViewDelete.Visible = False
                            mnuListViewDelete.Enabled = False
                        End If
                    Else
                        ' The user is not directly on an item so show only
                        ' the "Add Item" selection.
                        mnuListViewSetActive.Visible = False
                        mnuListViewSetActive.Enabled = False
                        mnuListViewSetInactive.Visible = False
                        mnuListViewSetInactive.Enabled = False
                        mnuListViewWriteValue.Visible = False
                        mnuListViewWriteValue.Enabled = False
                        mnuListViewDelete.Visible = False
                        mnuListViewDelete.Enabled = False
                    End If
                
                ' Show the popup
                frmMain.PopupMenu mnuListView
                
                End If
            End If
        End If
    End If
End Sub


' The mnuListViewSetActive_Click directly changes the active state of
' the selected OPC item.  This is done by calling the .SetItemActiveState
' of the selected OPCItemClass object.
'
Private Sub mnuListViewSetActive_Click()
 
    ' Make sure an item is selected.
    If Not Module1.SelectedOPCItem Is Nothing Then
        ' Change its active state to True.  Normally you will want to call
        ' this function only once with out an associated call to make the item
        ' inactive.  This however is not a requirement and you can call this
        ' function on an item as many times as you like. The next call
        ' with the state set to False will still turn the item off.
        Module1.SelectedOPCItem.SetItemActiveState (True)
    End If
    
End Sub


' The mnuListViewSetInactive_Click directly changes the active state of
' the selected OPC item.  This is done by calling the .SetItemActiveState
' of the selected OPCItemClass object.
'
Private Sub mnuListViewSetInactive_Click()
    
    ' Make sure an item is selected.
    If Not Module1.SelectedOPCItem Is Nothing Then
        ' Change its active state to False.  Normally you will want to call
        ' this function only once with out an associated call to make the item
        ' active.  This however is not a requirement and you can call this
        ' function on an item as many times as you like. The next call
        ' with the state set to True will still turn the item on.
        Module1.SelectedOPCItem.SetItemActiveState (False)
    End If
    
End Sub


' This sub simply displays the frmWriteItem form.
'
Private Sub mnuListViewWriteValue_Click()
    'Module1.SelectedOPCItem will be set if this event occurs.
    Load frmWriteItem
    frmWriteItem.Show
    ' Prevent the tree view from being selected while the write item
    ' menu is displayed
    '
    ' You'll see that I check this property in the lvListView_MouseUp
    ' as a simple way of preventing user input in the listview without
    ' using the .Enabled property of the ListView which cause the
    ' whole thing to grey out.
    tvTreeView.Enabled = False
End Sub


' This sub directly removes an OPCIemClass object from the selected
' OPCGroupClass object.
'
Private Sub mnuListViewDelete_Click()
    On Error GoTo SkipItemDelete
      
    Dim Result As Boolean
    Dim Error As Long
    ' Attempt to remove the selected OPCItemClass object from the
    ' selected OPCGroupClass object by passing in the item key to the
    ' .RemoveOPCItem function of the class.
    Result = Module1.SelectedOPCGroup.RemoveOPCItem(lvListView.SelectedItem.Key, Error)
    ' If teh item was removed then remove it from the list view.
    If Result = True Then
        Set Module1.SelectedOPCItem = Nothing
        lvListView.ListItems.Remove (lvListView.SelectedItem.Key)
    End If
    
SkipItemDelete:
End Sub


' This sub is invoked from the mnuListView popup context menu
' and simply displays the frmAddItem form.
'
Private Sub mnuListViewNewItem_Click()
    Load frmAddItem
    frmAddItem.Show
    ' Prevent the tree view from being selected while the Add item
    ' menu is displayed
    '
    ' You'll see that I check this property in the lvListView_MouseUp
    ' as a simple way of preventing user input in the listview without
    ' using the .Enabled property of the ListView which cause the
    ' whole thing to grey out.
    tvTreeView.Enabled = False
End Sub


' The timer routine is used to update the contents of the list view display
' based on the contents data in the OPCItemClass objects attached to the
' selected OPCGroupClass object.  Normally we could allow the actual update
' of the contents of the OPCItemsClass object do the updating of the listview
' but the flashing would be really bad.  So I chose to use a timer tick
' to update the display. It still flashes but not a badly.  There are ways to
' prevent the flashing but they go beyond the scope of this example.
' The other little pain you'll notice is that you can't scroll the list
' unless you select an Item at the bottom of each page of the list.  I was
' not able to find a way to remove the selection from the item so the list
' could be scrolled easily.  When a listview item is selected the list view
' tries to get that value in the view.
'
Private Sub Timer1_Timer()
    On Error GoTo SkipDisplayUpdate
    
    Dim OPCGroupItemsCls As Collection
    
    ' Make sure a group is selected before any update occurs.
    If InStr(tvTreeView.SelectedItem.Key, "Group") Then
    
        Dim OPCGroupToUpdate As OPCGroupClass
        Dim OPCItemData As OPCItemClass
        Dim OPCServerGroupsCls As Collection
        
        ' Get the OPCItemClass object collection from the selected OPC group
        Set OPCServerGroupsCls = Module1.SelectedOPCServer.GetOPCServerGroupCollection
        Set OPCGroupToUpdate = OPCServerGroupsCls.Item(tvTreeView.SelectedItem.Key)
        Set OPCGroupItemsCls = OPCGroupToUpdate.GetOPCGroupItemsCollection
        
        ' If there aren't any items in the group skip the update
        If OPCGroupItemsCls.Count = 0 Then
            GoTo SkipDisplayUpdate
        End If
        
        ' only update those items that are within the display area of the
        ' list view.
        Dim itmX As ListItem
        ' Get the first Listitem in the ListView display
        Set itmX = lvListView.GetFirstVisible
         
        ' This should contain a valid ListItem but just in case testing
        ' it is always a good idea.
        If Not itmX Is Nothing Then
            Dim NumLinesDisplayed  As Integer
            ' This a hack, normally you would get the font metric for
            ' the system font, get the height and calculate the number
            ' of lines in the display area.  I didn't want to do this
            ' at the time so here's a rough estimate of the value.
            NumLinesDisplayed = (lvListView.Height / 214)
            
            Dim i As Integer
            Dim a As Integer
            Dim GroupItemIndex As Integer
            Dim OPCItemToUpdate As OPCItemClass
            Dim Quality As Long
            Dim ItemValue As Variant
            a = itmX.Index
            
            ' See if the user is scrolling up or down and change the
            ' selected ListView item to allow the view to move beyond the
            ' current items in the view.
            If LastTopItem <> a Then
                If LastTopItem <> -1 Then
                    Set lvListView.SelectedItem = itmX
                End If
                LastTopItem = a
            End If
                       
            For i = 1 To NumLinesDisplayed
                ' Get the ListItem key which is in the form "Item X"
                ' Since the OPCItemClass collection is key on a string
                ' value of just "X" we must remove the "Item" portion
                ' and conver thenumber back to a string.
                GroupItemIndex = Val(Mid(itmX.Key, InStr(itmX.Key, " ")))
                ' Now that we have the key as a string we can get the
                ' OPCItemClass object associated with this listview item.
                Set OPCItemToUpdate = OPCGroupItemsCls.Item(Str(GroupItemIndex))
                
                ' With the OPCItemClass object in hand we can update the list
                ' view item.  For both the ItemValue and the Quality value
                ' I use the Const OPCItemLocal which forces the OPCItemClass
                ' functions to return their local copies of the data value and
                ' quality.
                ItemValue = OPCItemToUpdate.GetItemValue(OPCItemLocal)
                
                ' If the ItemValue is not an array then simply use the Variant
                ' type to update the list box sub item 1 which the Value Heading.
                If Not IsArray(ItemValue) Then
                    itmX.SubItems(1) = ItemValue