frmmain.frm

VB开发OPC Client的教程和源码

         Caption         =   "-"
      End
      Begin VB.Menu mnuListViewDelete 
         Caption         =   "&Delete"
      End
   End
End
Attribute VB_Name = "frmMain"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
' The main form frmMain is the central user interface focal point
' for this example application. While all of the actual OPC
' interface code is contained in the three class modules
' OPCServerClass, OPCGroupClass, and OPCItemClass, the use
' of these classes is demostrated primarily in this module.
' Think of this module as being the basis for your own OPC
' application.  While your application may not have the same
' user interface requirements, the mechanisms for adding server
' connections, groups, and items is the same.  One thing to
' keep in mind is that while this example applicaiton
' demonstrates the various OPC elements driven by User input
' your application can do all of these steps programtically,
' or via configuration files, or database contents.
'
' The primary bodies of code in this form deal with managing
' user interaction with the tvTreeView and lvListView controls
' on this form.  That management includes maintaining the
' OPC server, group, and item objects stored in these views.
' As you add server connections, groups and items, both the
' class modules and the TreeView and ListView controls are kept in
' sync with these item.  Simply put the TreeView and ListView
' contain a collection of objects but the OPC class modules
' keep their own list so you don't need to have any user interface
' elements for your own OPC application.
'
' As part of managing the user interface, the frmMain module
' also handles determining what OPC server, group or item has been
' selected by the user.  Once determined the three variables in
' Module1.bas,  SelectedOPCServer, SelectedOPCGroup,
' and SelectedOPCItem will be set accordingly.  These variables
' are important in other parts of this example application.  While
' not used in the three class modules, these variables are used in
' the other VB forms of this application to determine what object
' the user has selected for modification or use.
'
' One important element of how the user interface interface for
' this example is the use of the key string used on the Node
' items for the tvTreeView and on the ListItems for the lvListView.
' These key have been given very specific names with a number. In the
' TreeView there are two types of keys by name "Server X" and
' "Group X Y".  For the server key the Key always contains the word
' "Server" plus some number.  For group items the Key always
' contains the word "Group" plus a group number and the server
' number.  For this example it is crucial that these not be changed
' as all object selection is based on using these key to identify
' selected  object.  I give more detail below but it worth mentioning
' the now due to its importance.
'
' Only this form contains a menu bar.  If you have already run the
' application you have seen that there is very little in the menus.
' If you look at the menu bar in the menu editor you will see that
' there a great deal of hidden(popup) menus.  These popup menus are
' invoked by right clicking in either the tvTreeView or the lvListView.
' These right click context menus are used as the primary method of user
' interaction within the application.  Normally you would mimic these
' menus on the menu bar and I would have as well but you then must
' also take care of enabling and disabling them as needed.  I felt that
' the extra code would have clouded the application so I provide
' only the context menus.
'
' At the end of this module is some code generated by the VB app
' wizard, I have placed this code at the end of this module.
' It deals with the resizing of the this applications client
' space but has nothing to do with OPC connectivity.


Option Explicit
Option Base 1

' These variables are used in the standard code generated by
' VB to handle moving the splitter bar on the this form.
Dim mbMoving As Boolean
Const sglSplitLimit = 500
Dim LastTopItem As Integer


' On form load we need to get the last size of the application we
' also need to add the heading to the lvListView control.
'
Private Sub Form_Load()
    Me.Left = GetSetting(App.Title, "Settings", "MainLeft", 1000)
    Me.Top = GetSetting(App.Title, "Settings", "MainTop", 1000)
    Me.Width = GetSetting(App.Title, "Settings", "MainWidth", 7500)
    Me.Height = GetSetting(App.Title, "Settings", "MainHeight", 6500)
    
    ' Add the three OPC heading to the lvListView control
    ' The ItemID is the fully qualified Item identification string
    ' for an OPC item.  The Value heading is the current value
    ' of the item. The Status heading is Quality value of the
    ' OPC item.
    lvListView.ColumnHeaders.Add , , "ItemID", lvListView.Width / 3
    lvListView.ColumnHeaders.Add , , "Value", lvListView.Width / 3
    lvListView.ColumnHeaders.Add , , "Status", lvListView.Width / 3
    lvListView.View = lvwReport ' Place list view text report mode
    
    ' This variable is used to determine when the user is attempting
    ' to scroll the OPC Item window.  When the window is scrolled the
    ' currently selected OPC Item must be deselected to allow the
    ' scroll beyond the selected item.  If the selection isn't cleared
    ' the ListView control won't allow the list to be scrolled.  Normally
    ' you don't notice this because the list view isn't normally being
    ' updated continuously.
    LastTopItem = -1
End Sub


' The unload forms sub handles cleaning up for the application.
' From an OPC standpoint it releases each OPCServerClass object
' contained in the OPCServers collection.  Due to the design of
' the OPCServerClass object it in turn releases any OPC groups
' and items those groups may contain.
'
' This is a good catch all for your application but normally
' you should not rely on this call to cleanup your OPC connections.
' The best practice is to specifically release the OPC items from
' your groups then release the groups from your servers and finally
' disconnect the OPC servers from your application.  This will be
' demonstated in the various delete functions for each of the
' objects.
'
Private Sub Form_Unload(Cancel As Integer)
    Dim i As Integer

    ' When exiting your application you should ensure that all
    ' groups and items are removed from the OPCServer objects
    ' then remove the OPCServer objects. The OPCServerClass
    ' contains a cleanup section in its terminate routine that
    ' will remove all groups and items from the class when the
    ' object is deleted. As we remove OPCServerClass object from
    ' the OPCServers collection this terminate function is called
    ' automatically removing We still need to remove the
    ' OPCServerGroups collection that contains the
    ' OPCGroupClasss objects ourselves.
    If OPCServers.Count <> 0 Then
        Dim a As Integer
        a = OPCServers.Count
        For i = 1 To OPCServers.Count
            With OPCServers
                ' Make sure we disconnect from server before we remove it
                Set Module1.SelectedOPCServer = .Item(a)
                Module1.SelectedOPCServer.DisconnectOPCServer
                .Remove (a)
                a = a - 1
            End With
        Next i
    End If
            
    ' Close all sub forms
    For i = Forms.Count - 1 To 1 Step -1
        Unload Forms(i)
    Next
    
    ' Save the current size of the application for the next load but
    ' only if the application is not in a minimized state.
    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
End Sub


Private Sub tvTreeView_Collapse(ByVal Node As ComctlLib.Node)
    ' When a server is selected we set the Module1.SelectedOPCGroup
    ' to nothing and clear the lvListView control.
    Set Module1.SelectedOPCGroup = Nothing
    ' Clear the current view of tags if any.
    lvListView.ListItems.Clear
    
End Sub

' This sub is the primary focal point for user interaction with the
' OPC server and goup objects. Depending on where you click within the
' tree view you will be presented with differing context menus that will
' allow you to add new servers, add new groups, view the properties of
' these objects or delete them.  Clicking within this view also allows
' you to select different objects and change the data you see in the
' lvListView control.
'
Private Sub tvTreeView_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
    ' The SelectedNode var is used to hold the Node item returned from
    ' the HitTest
    Dim SelectedNode As Node
    ' When the selected node is group node this var will be used to
    ' hold the parent node of the selected group, ie. what server the group
    ' belongs to.
    Dim NodParent As Node
    ' Once a group and server are determined the NewGroupSelection is used
    ' to hold the selected group.  This is then testing against the
    ' Module1.SelectedOPCGroup variable.  If they differ then a new
    ' lvListView list will potentially be build by the GetNewItemList
    ' function.  This allows you to select different groups and see
    ' the items for these groups in the lvListView control.
    Dim NewGroupSelection As OPCGroupClass

    ' Used to temporary provide access to the group collection of
    ' the OPCServerClass object pointed to by Module1.SelectedOPCServer.
    Dim OPCServerGroupsCls As Collection



    ' Determine if the user has selected a node form the tree view.
    Set SelectedNode = tvTreeView.HitTest(X, Y)

    ' Right button actions select server and group object and
    ' display the various context menus.
    If (Button = vbRightButton) Then
        ' In all cases the "New Server Connection" menu selection
        ' is available.
        mnuTreeViewNewServer.Visible = True
        mnuTreeViewNewServer.Enabled = True
        
        ' If the user has selected a node as indicated by
        ' SelectedNode not being nothing then determine what type
        ' of node was selected.  This is where the Key name I mention
        ' in the start of this module really comes into play.  By
        ' knowing that all server nodes have the word "Server" as part
        ' of their Key and all group nodes have the word "Group" as part
        ' of their Key we can easily determine what type of node the user
        ' has selected.
        If Not SelectedNode Is Nothing Then
            ' Check for a server node
            If InStr(SelectedNode.Key, "Server") Then
                ' When we get to the AddSelectedOPCServer function
                ' you will see that I also use this same KEY within
                ' in the OPCServers collection to key the server.
                ' This make selection of the server from the collection
                ' as easy as what you see in the next three lines.
                ' In your application you can of course use any keying
                ' methodology you desire as long as their unique and
                ' you manage them.
                With OPCServers
                    Set Module1.SelectedOPCServer = .Item(SelectedNode.Key)
                End With
                
                ' When a server is selected we set the Module1.SelectedOPCGroup
                ' to nothing and clear the lvListView control.
                Set Module1.SelectedOPCGroup = Nothing
                lvListView.ListItems.Clear
                
                ' Now enable all of the options that the user can use when
                ' a server connection has been selected.
                mnuTreeViewNewGroup.Visible = True ' Add group allowed
                mnuTreeViewNewGroup.Enabled = True
                mnuTreeViewDelete.Visible = True    ' Deleted the Server
                mnuTreeViewDelete.Enabled = True
                mnuTreeViewProperties.Visible = True 'Display Server Properties
                mnuTreeViewProperties.Enabled = True
                mnuTreeViewNewItem.Visible = False   ' New Items can't be added at this time
                mnuTreeViewNewItem.Enabled = False
                
            ' If a server hasn't neen selected then it must be a group
            ' node.  We test the node key just to be sure.
            ElseIf InStr(SelectedNode.Key, "Group") Then
                ' Get a reference to the parent of group node.
                Set NodParent = SelectedNode.Parent
                ' Set the Selected Server to this parent easy stuff as
                ' long as the keys are managed and not lost.
                With OPCServers
                    Set Module1.SelectedOPCServer = .Item(NodParent.Key)
                End With
                
                ' Now that we know the server connection we need to access
                ' the OPCGroupClass collection contained in that
                ' OPCServerClass object.
                Set OPCServerGroupsCls = Module1.SelectedOPCServer.GetOPCServerGroupCollection
                ' The NewGroupSelection is simply used to test the newly
                ' selected group against a group that may already be selected.
                ' You'll notice right away that this use of the SelectedNode.Key
                ' is a little different from the simple use when selecting
                ' an OPC server.  You'll see why in the AddOPCGroupMain function
                ' below but here is the short answer.  When a node is added to the
                ' tree view control the Node.Key must be unique regardless
                ' of parent/child relationships or not.  As you'll see in the
                ' AddOPCGroupMain function the OPCServerClass.AddOPCGroup
                ' function returns a group key.  That key is specific
                ' to a single group and the server.
                Set NewGroupSelection = OPCServerGroupsCls.Item(SelectedNode.Key)
                
                ' Now that we have the OPCGroupClass object the user
                ' has selected we test to see if it is the currently