Learn Microsoft Access Advanced Programming Techniques, Tips and Tricks.

Creating Access Menu with Tree View Control

The Microsoft Access Project Menu, when finished with the Tree View Control, will look like the Image given below.

The Image above shows the Report Group’s third Option Custom Report is selected and highlighted, with the Report Filter Parameter Form open, overlapping the Menu Screen, for the User’s input.

Before going into that, in last Week’s Lesson, we learned how to organize the related items in hierarchical order, using Microsoft Tree View Control, based on the Sample data Table. 

I made a point last week, that the related items in Tree View control’s data need not necessarily be next to each other.  After this, you will be more clear about how to update Relative Keys of Child Nodes, irrespective of the physical position of the records in the Table, but based on the relationship with its Parent Node IDs. 

This was the Data Table that we used and finished with last week’s exercise:

Can you add the following list of items at the end of the above table and update their ParentID field values, so that the TreeView Control display will look like the sample image given below:

New records for Table item record related field:

  1. Text Field.
  2. Number Field.
  3. Date/Time Field.
  4. Hyperlink Field.

Form-related Controls:

  1. Text Box.
  2. Command Buttons.
  3. Combo Box.
  4. List Box.

Report related Controls:

  1. Text Box.
  2. Label.
  3. Graph Chart.

Assign ParentID Values to these items so that the Tree View Display looks like the following Image:

Now, we will proceed with the creation of an MS-Access Project Menu and learn what it takes to create one. A simple Menu Image is given below:

It is a simple Menu with only three groups of options: Forms, Report Views, and Macros. 

Under Forms Group two options are given, the first one displays the Tree View controls Menu table record.  The second option displays the same records in continuous form mode.

The first option under Report View displays a Report on products Category records, from the Categories Table of NorthWind.accdb database.

The second option displays the Products List-Price Report.

The third option opens a Parameter Form so that the User can set the Minimum and Maximum List-Price values range, to Filter data for the Products List-Price Report.

Under the Macros Processes Group, both options run Macro1 and Macro2 respectively, and display different messages.

We need a Menu Table with the above option records with some additional fields, besides the usual TreeView’s Unique IDs, Description, and ParentID data fields.  The Menu Table Image is given below:

Create a Table with the above structure, add the above records, and save it with the name Menu.  The ID field is Auto Number, PID, and Type fields are Numeric fields, others are Text Fields.

We are familiar with the first three Data Fields: the Unique ID, Description, and ParentID Fields. Here, I have shortened the ParentID field name to PID.

We need four more fields in the Menu Table, one field Type, for the object type Code, and three fields Form, Report, and Macro.

Type Field contains the Access Object Type Numeric Codes to identify the Option the User clicked on.

  • The Form field is Form Names, object Type code 1,
  • Report Field contains Report Names, object Type code 2,
  • Macro Field is Macro Names, object type code 3.

Note: All the object names can be put in one Column. We have used separate fields for clarity only.  If you do that then make changes in the VBA Code, wherever it references different field names.

Based on the code numbers we can pick up the Object Names, from their respective fields and call the DoCmd.Openform or Docmd.OpenReport or Docmd.RunMacro to execute the action on the Child Node Clicks.

Now, we need to store the Type Code and Object Name on the Child Nodes. We will take up that topic when we start Adding the Nodes to the Tree View control.

We need two more data Tables for sample Forms and Reports.  The Categories Table and Product Tables, from the NorthWind sample Database.  To save time I have attached the Demo Database with all the Objects and Programs at the end of this Page to Download and try it out.

Create two Forms using the Menu Table with the names Data Entry and another Form Data View in continuous Form mode.

Create two reports, one on the Categories Table with the report name: Categories, and another report on Products Table with the name Products Listing.  Add a long Label control below the main heading on the Products Listing Report and set the Name Property value to Range.

Create a small form with two unbound TextBoxes and change their name Property Value to Min & Max, like the design given below:

Add two Command Buttons as shown above.  Change the Caption Property Value of the first Button to Open Report and the Name Property Value to cmdReport.

Change the Second Command Button’s Caption to Cancel and the Name Property value to cmdCancel.

Display the Code Module of the Form.  Copy and Paste the following Code into the Form Module and save the Form:

Private Sub cmdOpen_Click()
Dim mn, mx, fltr As String
mn = Nz(Me![Min], 0)
mx = Nz(Me![Max], 9999)
If (mn + mx) > 0 Then
    fltr = "[List Price] > " & mn & " And " & "[List Price] <= " & mx
    DoCmd.OpenReport "Products Listing", acViewReport, , fltr, , fltr
Else
    DoCmd.OpenReport "Products Listing", acViewReport
End If

End Sub

Private Sub cmdCancel_Click()
DoCmd.Close
End Sub

When the User sets a Value Range by entering the Minimum and Maximum List Price range in their respective TextBoxes the Report Filter criteria String is created.  The Report Filter String value is passed to the Product Listing Report as an Open Report command Parameter.  The Filter String value is also passed as the OpenArgs (Open Argument) Parameter. 

The Filter parameter filters the Report Data, based on the Criteria, specified in Min & Max fields, and the open argument value is copied to the Range Label Caption when it opens the Report. 

Copy and Paste the following Code into the Product Listing Report’s VBA Module:

Private Sub Report_Open(Cancel As Integer)
    DoCmd.Close acForm, "Parameter"
    Me.Range.Caption = Nz(Me.OpenArgs, "")
End Sub
  1. Create a new form, with the name frmMenu, and add the Microsoft TreeView Control from the ActiveX Control’s List.  Resize the Control as shown in the Design View below:

  2. Change the Tree View Control’s name to TreeView0 in the normal Property Sheet.

  3. Add a Command Button below the Tree View control.  Change its Name Property Value to cmdExit and Caption Property value to Exit.

  4. Right-Click on the Tree View Control and highlight the TreeCtrl_Object option and select Properties to display the Property Sheet.

  5. Change the following Property Values as given below:

  • Style = 7 (tvwTreeLinesPlusMinusPictureText)
  • Line Style = 1 (tvwRootLines)
  • LabelEdit = 1 (tvwManual)

Last week we have changed the first two Property Values.  When LabelEdit Property’s default value is 0 -  tvwAutomatic, Clicking on the Node twice (not double-click) the Node-Text will go on Edit Mode and you can change the Text.  But it will not directly update the data source field.  By changing it to 1 – tvwManual will prevent it from going into edit mode.

We can change this through Code by adding the following lines in the Form_Load() Event Procedure:

With Me.TreeView0.Object
    .Style = tvwTreelinesPlusMinusPictureText
    .LineStyle = tvwRootLines	
    .LabelEdit = tvwManual
End With

Last week we have used the Form_Load() Event Procedure to read the Tree View Node values to create the Root-level and Child Nodes.  We need the same Procedure here also with a few lines of additional Code.

Besides that, we need to trap the Node_Click() Event of Nodes to check which Option the User has selected.

Copy and Paste the following VBA Code into the Form Module and save the Form.

Option Compare Database Option Explicit Dim tv As MSComctlLib.TreeView Const KeyPrfx As String = "X" Private Sub Form_Load() Dim db As Database Dim rst As Recordset Dim nodKey As String Dim PKey As String Dim strText As String Dim strSQL As String Dim tmpNod As MSComctlLib.Node Dim Typ As Variant Set tv = Me.TreeView0.Object tv.Nodes.Clear

‘Change the TreeView Control Properties

With tv
    .Style = tvwTreelinesPlusMinusPictureText
    .LineStyle = tvwRootLines
    .LabelEdit = tvwManual
    .Font.Name = "Verdana"
End With

strSQL = "SELECT ID, Desc, PID, Type,Macro,Form,Report FROM Menu;" Set db = CurrentDb Set rst = db.OpenRecordset(strSQL, dbOpenDynaset) Do While Not rst.EOF And Not rst.BOF If Nz(rst!PID, "") = "" Then nodKey = KeyPrfx & CStr(rst!ID) strText = rst!Desc Set tmpNod = tv.Nodes.Add(, , nodKey, strText) 'Root-Level Node Description in Bold letters With tmpNod .Bold = True End With Else PKey = KeyPrfx & CStr(rst!PID) nodKey = KeyPrfx & CStr(rst!ID) strText = rst!Desc Set tmpNod = tv.Nodes.Add(PKey, tvwChild, nodKey, strText) 'Check for the presense of Type Code If Nz(rst!Type, 0) > 0 Then Typ = rst!Type Select Case Typ Case 1 'save type Code & Form Name in Node Tag Property tmpNod.Tag = Typ & rst!Form Case 2 'save type Code & Report Name in Node Tag Property tmpNod.Tag = Typ & rst!Report Case 3 'save type Code & Macro Name in Node Tag Property tmpNod.Tag = Typ & rst!Macro End Select End If End If rst.MoveNext Loop rst.Close Set rst = Nothing Set db = Nothing End Sub Private Sub cmdExit_Click() If MsgBox("Close Menu Form? ", vbYesNo, "cmdExit_Click()") = vbYes Then DoCmd.Close End If End Sub Private Sub TreeView0_NodeClick(ByVal Node As Object) Dim varTag, typeid As Integer Dim objName As String, nodOn as MSComctlLib.Node If Node.Expanded = False Then Node.Expanded = True Else Node.Expanded = False End If

‘Reset the earlier lighlight to normal

For Each nodOn In tv.Nodes
    nodOn.BackColor = vbWhite
    nodOn.ForeColor = vbBlack
Next

‘changes BackColor to light Blue and ForeColor White

tv.Nodes.Item(Node.Key).BackColor = RGB(0, 143, 255)
tv.Nodes.Item(Node.Key).ForeColor = vbWhite

‘—Highlight code ends-

varTag = Nz(Node.Tag, "") If Len(varTag) > 0 Then typeid = Val(varTag) objName = Mid(varTag, 2) End If Select Case typeid Case 1 DoCmd.OpenForm objName, acNormal Case 2 DoCmd.OpenReport objName, acViewPreview Case 3 DoCmd.RunMacro objName End Select End Sub

The Tree View Object is declared in the Global Declaration Area of the Module.  A constant variable KeyPrfx is declared with the value “X”.

The Form_Load() Event Procedure of last week’s Article we have modified with additional Code.  I have commented on the new Code segment to give an indication of what it does but will explain what it does.

The Procedure declares Database, Recordset, and four String Variables.  The Next two lines declare a temporary Node Object: tmpNod and Typ Variant Variables are declared.

Next, the TreeView Object tv is assigned to the TreeView0 Object on the Form.  The TreeView0’s existing Nodes, if any, are cleared with the statement: tv.Nodes.Clear, in preparation for loading all the Nodes again.

We have implemented the following Code to modify the Tree View control’s Properties through the Code, rather than through the Property Sheet.

With tv
    .Style = tvwTreelinesPlusMinusPictureText
    .LineStyle = tvwRootLines
    .LabelEdit = tvwManual
    .Font.Name = "Verdana"
End With 

The Tree View Font is changed to Verdana. Besides that, we will bring in some more functions like expanding or collapsing all the Menu Groups with one click, rather than manually expanding or collapsing one group after the other.

The new SQL String is modified to add the new Fields Type, Form, Report, and Macro Fields from Menu Table.

The Menu Table’s first record is checked for the presence of any value in the PID field, if it is empty then it is a Root-level Node record. It is added to the Tree View Object as the Root level Node and its reference is saved in the tmpNod Object.

The Node has several properties like Forecolor, Bold, and several others out of that we have taken the Bold Property and assigned True to make the Root level Node look different than its Child Nodes.

If it is not a Root Node entry, then it has the PID value, the program takes the Else clause and the record is added as a Child Node.  Here, we check the Type field value.  If it contains one of the three values 1, 2, or 3 then we must take the value from the Form, Report, or Macro Name along with the Type Code and concatenates them together  (like ”1Data Entry”, “2Category Listing” etc.) and save it in the Tag Property of Child Nodes.  We are familiar with the Tag Property in Access controls, like TextBoxes, Labels, Command Buttons, and others, but we rarely use it.

The cmdExit_Click() Procedure closes the Menu Form if the response from the User is affirmative.

When the user clicks on a Child Node, the value we have saved in its Tag Property must be extracted and checked to determine what to do next.  For this, we need a TreeView0_NodeClick() Event Procedure.

Private Sub TreeView0_NodeClick(ByVal Node As Object) Dim varTag, typeid As Integer Dim objName As String, nodOn as MSComctlLib.Node If Node.Expanded = False Then Node.Expanded = True Else Node.Expanded = False End If

‘Reset the earlier lighlight to normal

For Each nodOn In tv.Nodes nodOn.BackColor = vbWhite nodOn.ForeColor = vbBlack Next nodOn

‘changes BackColor to light Blue and ForeColor White tv.Nodes.Item(Node.Key).BackColor = RGB(0, 143, 255) tv.Nodes.Item(Node.Key).ForeColor = vbWhite ‘—Highlight code ends- varTag = Nz(Node.Tag, "") If Len(varTag) > 0 Then typeid = Val(varTag) objName = Mid(varTag, 2) End If Select Case typeid Case 1 DoCmd.OpenForm objName, acNormal Case 2 DoCmd.OpenReport objName, acViewPreview Case 3 DoCmd.RunMacro objName End Select End Sub

The Click() Event Procedure receives the clicked Node’s Reference as a Parameter in the object Node.  At the beginning of this procedure, we have declared a few Variables.

In the next few lines, check whether the clicked Node is in an expanded or collapsed state.

Normally, to expand a Node, to show its hidden child Nodes, either we click on the + (plus symbol) at the left side of a Node or double-click on the Node itself.  Double-Clicking on the Node again or clicking on the – (minus symbol) will hide the Child Nodes.

With the following Code segment we can expand or collapse Child-Nodes with a Single click:

If Node.Expanded = False Then
    Node.Expanded = True
Else
    Node.Expanded = False
End If 

The next six executable lines ensure that the Node that received the Click remains highlighted.

‘Reset the earlier Highlight to Normal

For Each nodOn In tv.Nodes nodOn.BackColor = vbWhite nodOn.ForeColor = vbBlack Next nodOn

‘Changes BackColor to light Blue and ForeColor White tv.Nodes.Item(Node.Key).BackColor = RGB(0, 143, 255) tv.Nodes.Item(Node.Key).ForeColor = vbWhite ‘—Highlight code ends-

Next, The varTag Variable is assigned with the Tag Property value. If it is not empty then the value is split into two parts. The Numeric value is extracted and saved in the Typid variable and the Object Name part is saved in the variable objName.

Depending on the value in the Typid variable the Docmd is executed to open the Form, Report, or Run the Macro.

We will add two more Command Buttons on the top of the Menu. One to expand all the Nodes with one Click and the second one to collapse all the Nodes.

  1. Add two more Command Buttons at the top area of the Tree View Control as shown in the design below.
  2. Change the Name Property Value of the left Command Button to cmdExpand and the Caption to Expand All.
  3. Similarly, change the right-side Command Button’s Name Property to cmdCollapse and the Caption to Collapse All.
  4. Copy and Paste the following VBA Code below the existing Code in the frmMenu Form Module and save the Form.
Private Sub cmdExpand_Click()
Dim Nodexp As MSComctlLib.Node

For Each Nodexp In tv.Nodes
    If Nodexp.Expanded = False Then
        Nodexp.Expanded = True
    End If
Next Nodexp
End Sub


Private Sub cmdCollapse_Click()
Dim Nodexp As MSComctlLib.Node

For Each Nodexp In tv.Nodes
    If Nodexp.Expanded = True Then
        Nodexp.Expanded = False
    End If
Next Nodexp
End Sub

At the beginning of the cmdExpand_Click() Event, we have declared a Tree View Node object NodExp.  The For . . . Next loop takes one Node at a time and checks whether it is in expanded form or not.  If not, then its Expanded Property value is set to True.

Similarly, the cmdCollapse_Click() Event makes a similar check and if it is in an expanded state, then the Expanded Property value is set to False.

The full Tree View Control’s all Nodes can be expanded and makes all their child Nodes visible at once or all Child Nodes kept hidden except the Root-level Nodes.

Hope you enjoyed creating the new Menu for your Project.  If you run along the design task step-by-step, then your Menu should look like the finished Menu Image given at the top.

During the Year 2007, I designed a Menu in one of my Projects, for the Vehicles Service Contract System, using the Tab Control with several Pages. Each Page has 10 or more Options and to make each Page appear in turn in the same area when the user clicks on the Command Buttons lined up on either side of the Menu. Command Buttons on the right side also change, based on the selection of the left side Button.

Click to Enlarge

You can find the Menu Design with Tab Control Article on this Link:https://www.msaccesstips.com/2007/06/control-screen-menu-design.html


CLASS MODULE

  1. MS-Access Class Module and VBA
  2. MS-Access VBA Class Object and Arrays
  3. MS-Access Base Class and Derived Objects
  4. VBA-Base Class and Derived Object-2
  5. Base Class and Derived Object Variants
  6. MS-Access Recordset and Class Module
  7. Access Class Module and Wrapper Classes
  8. Wrapper Class Functionality

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Microsoft TreeView Control Tutorial

A. Introduction.

Microsoft Tree View Control is part of Microsoft Windows Common Controls. It is an interesting piece of Object that displays related data in a hierarchy of Nodes.  It can display related data, like entries and sub-entries in an Index List or listing of folders like Windows Explorer’s Left-Pane or a List of related Items in a hierarchical structure with Tree-Lines, Checkboxes, and Graphic Images.

The ListView and ImageList Controls are part of the Windows ActiveX Controls and we will be using them along with the TreeView Control in Microsoft Access. 

I think you would like to look at some sample TreeView Control Demo Images, which we will be working on building in the coming few weeks.

B. Sample Demo Images.

      Nodes in the Collapsed state.

  1. The Sample Demo TreeView Image with all Nodes in Collapsed form.

     Nodes in the Expanded View.

  2. The above TreeView Control Nodes in the expanded view.

    With Arrowhead Image Icons.

  3. The TreeView Sample Display, with arrowhead Image Icons displayed to the left of each Node Text.

    Root-Level Nodes Have Folder Images others with Arrowhead.

  4. Next, the TreeView Display with linked data in a Sub-Form.  Root level Nodes have two Images.  The Folder-closed Image is displayed in normal mode.  When the Root Level Node receives a Mouse Click it displays the Folder-open image and displays the Child-Nodes in expanded form. 

    Related information is displayed on the Sub-Form based on the selection of Root-level Node.

    One of the Child-Node items selected displays another Form (normally kept hidden) with related information.

    TreeView and ListView Controls.

  5. In the next picture of the Form, there are two Panels. The Product Category Item-related Nodes are in TreeView Control, in the left panel.  When one of the Category items receives a Click on the TreeView control, related Product Items with Quantity and List Price in separate Columns will appear in ListView Control, in the right-side Panel.

C. Creating Sample Data for Trial Run.

Let us try out the TreeView Control with some sample data shown below, based on the first two images shown at the beginning of this Page.

The above sample data table has three Fields.

  • The ID field is an AutoNumber field with Unique ID Numbers.  The AutoNumber type is selected for our convenience.  In either case, All records in the Table should have a Unique ID Value.  If it is Numeric then it should be converted into String Type, before adding it to the TreeView Control.

  • The Second field is Node Description (Desc). The rows of information in this Column are logically related. 

  • The third ParentID field is Numeric Type. But they should be converted to String Type before using it on TreeView Control.

We must know how the Description Column values are related to each other, based on that we can establish the relationship by entering related values into the ParentID field.

For example the logical arrangement of the relationship between the Author of Books, Publishers of the Books,  the Book Stores where the Books are on Sale, or like Relationship between members of a Family Tree. 

Relationship between Product Category, Products, Stock, Price, and so on. All this information may not appear under one Column in a single Table.  They may appear in different Columns or on different tables as well.

The ParentID field is very important in that it determines the hierarchical arrangement of Nodes. If the ParentID Field is empty, then that record should go as a Root-level Node.  The Child-Node always should have its ParentID filled in with its Parent records ID Value.

Root level Node can have one or more Child Node(s), and Child Node can have its own child Node(s).

We will load the above data into a TreeView Control and see how it looks.  Then we will fill up the ParentId field with related IDs to change the view, the way we want to see it in a logical order.

D. Windows Common Controls Library file.

  1. But, first thing first, open one of your Databases or create a new one.

  2. Open the VBA Window (ALT+F11) and select References… from the Tools Menu.

  3. Look for the File: Microsoft Windows Common Controls in the displayed list of files and put a checkmark to select it.

    If you could not find the file in the list, click Browse... Button and find the file: MSCOMLIB.OCX in the Windows System directory, for Windows 7 Version look for the file in the SysWOW64 folder.  Click OK to close the Library Files listing Control.

  4. Create a Table with the following structure:

  5. Save the Table with the name Sample.

  6. Fill the Table with the sample data of 12 records as shown on the data view Image above.

    E. Creating TreeView Control on Form

  7. Create a New blank Form.

  8. Click on the ActiveX Controls button from the Controls Group, find the Microsoft TreeView Control then select it.

  9. Click OK to insert a TreeView control on the Form.

  10. Drag the control down and to the right to leave some space at the top and left of the TreeView Control.  Drag the bottom right corner sizing handle towards the right and the bottom corner to make the control larger, like the sample image given below.

  11. Display the Property Sheet of the control and change its Name Property Value to TreeView0, if it is different there.

  12. Display the VBA Editing Window of the Form.

  13. F. Access VBA Code.

  14. Copy and Paste the following VBA Code into the Module overwriting the existing lines of code there:
    Option Compare Database
    Option Explicit
    
    Dim tv As MSComctlLib.TreeView
    Const KeyPrfx As String = "X"
    
    Private Sub Form_Load()
    Dim db As Database
    Dim rst As Recordset
    Dim strSQL As String
    Dim nodKey As String
    Dim ParentKey As String
    Dim strText As String
    
    Set tv = Me.TreeView0.Object
    
    strSQL = "SELECT ID, Desc, ParentID FROM Sample;"
    
    Set db = CurrentDb
    Set rst = db.OpenRecordset(strSQL, dbOpenDynaset)
    
    Do While Not rst.EOF And Not rst.BOF
        If Nz(rst!ParentID, "") = "" Then
            nodKey = KeyPrfx & CStr(rst!ID)
            strText = rst!Desc
            ‘Add the TreeView Root Level Nodes
            tv.Nodes.Add , , nodKey, strText
        
        Else
            ParentKey = KeyPrfx & CStr(rst!ParentID)
            nodKey = KeyPrfx & CStr(rst!ID)
            strText = rst!Desc
            ‘Add the Record as Child Node
            tv.Nodes.Add ParentKey, tvwChild, nodKey, strText 
            
        End If
        rst.MoveNext
    Loop
    rst.Close
    
    Set rst = Nothing
    Set db = Nothing
    
    End Sub
    
    
  15. Save the Form with the name frmSample, but don’t close the VBA Window.

    G. VBA Code Line-by-Line.

Let us take a quick look at the VBA Code and understand what it does.

In the Global Declaration Area, of the Form Module, the Variable tv is the TreeView Object declaration.  The KeyPrfx is declared as Constant, with String Type value “X”. 

The TreeView Node’s Key-Value must be always of String Type and needs at least one non-numeric character present in the Node Key.  Our sample Table Key Values are all in numeric form, we can convert and add them to the Constant value “X”.  Numeric Value converted into String Type alone will not accept as Node-Key.

Note: If the Node-Key and Parent-Key values are already in Alpha or Alphanumeric form then the question of conversion doesn’t arise.  All Node-Key values must be Unique.

In the Form_Load() Event Procedure, the Database and Recordset objects are declared.  Four String Variables are also declared.

The statement Set tv = Me.TreeView0.Object statement assigns, the TreeView0  Object on the Form, to the object variable tv.

The OpenRecordset() statement opens the Sample Table Records using the SQL strSQL.

The Do While… statement ensures that the record set is not empty, if empty then exit the Loop and end the Program.

If there are records then the first record’s ParentId field is checked for the presence of some value there or not.

If it is empty then that record is TreeView control’s Root-level Node item.  The Root level Node needs only the unique Node-Key Value, which we already have in the ID Field and Item Description Field value for Text Argument.

If the ParentID field has a value, then the record is a Child-Node (Child of Root-level Node, or a child of some upper-level Child Node) of the TreeView Object. 

The next line creates the Key Argument Value in the nodKey String Variable, with the ID field Value,  converted into a String and added to the constant prefix X, Node-Key becomes X1.

The rst!Desc field value added to the String Variable strText, simply for clarity and to make it short in the Nodes.Add() method’s Parameter listing, if the field reference is very long then this will keep the Add() method neat and tidy.

The next executable line: tv.Node.Add() calls the Add() method of the TreeView.Nodes Object to add the Node to TreeView0 Control on the Form frmSample

The Syntax of the Add() method is given below for reference:

tv.Nodes.Add([Relative],[Relationship],[Key],[Text],[Image],[SelectedImage]) As Node

All six Parameters of the Add() method are optional.  If you call this method without any parameters, then an Empty Root-level Node will be added and a blank tree-line will appear as an indicator in the TreeView control.

For TreeView Root Level Node requires the Key and Text Argument values.

For the Child Nodes, both [Relative] and [Relationship] Arguments are required. Omitting any one of them will insert the Node as a Root Node, but will not generate any error.

[Relative] is the NodKey of an existing Node, entered into the related record’s ParentID field.  [Relationship] is a Constant tvwChild with numeric value 4, identifying it as a Child Node of Key-Value in ParentID Field.

The other Constant values for the Relationship Argument are used for positioning Child Nodes in a specific location.  Constant Values are as follows:

tvwFirst = 0,  places it as the first Node, at the level of the relative Node.

tvwLast = 1,  places as the last Node, at the level of the relative Node.

tvwNext = 2,  places the Node after a specified Node.

tvwPrevious = 3, places the Node immediately preceding the specified Node.

Note: You may experiment by setting each Value in the Relationship Argument and running the Code in Debug Mode, after keeping the VBA Window and Form in Normal View side by side. Watch how the Nodes are getting arranged in each cycle of the code execution to understand. 

These will be useful while editing the TreeView Control by Deleting an Item and inserting another item in its place or adding a new Node at a specific location.

A Node with [Relative] Key must exist in the Nodes Collection before attempting to add a child node,  to that parent Node, otherwise the Add() method generates an error.

This process is repeated till all the records are processed in the record set.

Note: You may review the VBA Code again after the Demo Runs.

H. The First Trial Run.

Open the Form in Normal View.  The Trial Run result will look like the Image given below.

It doesn’t look more than a normal Listbox.  Remember, we have not filled in any value in the ParentID field in our Sample Table.  We have to establish some relationship between the Items in the rows of Record to move and position them in a hierarchical order in the TreeView Control.

I. Understanding the Relationship between Records.

  1. Open the Sample Table and let us examine the Records and how they are related.
  2. Let us leave the Database item alone as a Root Item.

    The Database Object also has some top-level objects: Application, DBEngine, Workspaces Collection, and Databases Collection, which we have omitted here.

  3. Then we have the Tables group Item with ID value 2.
  4. In the next Table, Fields, Field items are related to the Tables group.  We want the Table, Fields, and Field items to line up under the parent Item Tables Group Record with ID value 2.
  5. Let us call the record Tables as the Parent Node, Table, Fields, and Field records as Child-Nodes.

    J. Updating the ParentID Field. 

  6. So we need to update the value 2 (Node-Key of Tables) in the parent ID field of Table, Fields, and Field records.
  7. Please update only those records and close the Table.  When it is done the records will look like the Image given below:
  8. Now, open your frmSample in Form View and check the TreeView Control.  The result will look like the earlier one without any change.  The changes already happened, but it is not visible to you.

    K. The Property Sheet of TreeView Control.

  9. The TreeView Control has its own Property Sheet and the settings influence its appearance.  So we will make a change in one of its Properties, and come back to the Tree View again.

  10. Turn the frmSample in Design View.
  11. Right-Click on the TreeView Control and highlight TreeCtrl_Object from the Shortcut Menu and select Properties.

    The Property Sheet will look like the Image given below:

  12. The Settings on this Property Sheet change the appearance of the TreeView Display.

    The left-side top Property Style is already set with the maximum features available Option-7 (tvwTreeLinesPlusMinusPictureText).

  13. Change the LineStyle Property Value = 1 (tvwRootLines) and Click the Apply button, then click OK to close the Property Sheet.

    L. Run After the LineStyle Property Value Change

  14. Save the Form and open it in Normal View.  Now, the Tree Lines appear correctly.  The Tables Node has a plus (+) sign on the left side, indicating that this Node has one or more Child Nodes in the next level and they are not in expanded form.
  15. Click on the plus symbol to expand the Node and display the Child Nodes, with the same ParentID.  When you click on the Minus Symbol the Child Nodes are collapsed and hidden, changing the symbol with a plus sign again.
  16. The display will look like the following Image when expanded:

    M. The Parent ID Updating of Other Records.

    We will update the Forms record ID Value (Node-Key Value) into Form, Controls, and Control records’ ParentID fields so that these records will list under the Forms Node as its Child Nodes.

    Similarly, update the ParentID field of the Report, and Control records with Reports ID (Node-Key Value) Value so that Report and Controls items will position under the Parent Node Reports, as its Child Nodes.

  17. Make changes to your Sample table records with the Parent ID values as shown below:

    After the above changes, the TreeView Display will look like the following Image, when all the Nodes are in expanded form.

    All Child Nodes related to the Root level Nodes: The Tables, Forms, and Reports are grouped as a list under their Parent Nodes.  But a Child Node may have a parent Node, a grandparent Node, or a Great grandparent Node.

    N. Arranging All Object in Logical Hierarchical Order.

    For example, let us take the first Root-level Node Tables.  Logically Field (with record ID 5) is directly related to the Fields collection (record ID 4), the Fields collection is related to Table and Table is part of Tables collection.  Each item in the group (record number 5 to 2) is related one step up to the next level.

    So let us position these Child Nodes correctly under their own Parent Node and see how it looks.

  18. Open your Sample Table and change the ParentID values of the Tables related to Child Records as shown below:

  19. The Field with ID-5 record’s Parent is Fields, record with ID-4, hence we have updated the 5th record’s ParentID field with ID Number 4.
  20. Similarly, the 4th record’s ParentID field is updated with 3, and the 3rd Record’s ParentID is updated with record number 2.
  21. Note: Don't assume that the items arranged in this way must be next to each other.

  22. After changes to the records save the Table and Open the frmSample to view the changes.  Your Tree View display should look like the image given below, with all Nodes in expanded form.

The Child-Node of a Root level Node can be a Parent-Node to its own Child or Children.  This way it can go several steps down the tree.

Change the other two groups of Child Node's ParentID field values to look like the Image given above.

Download TreeView Demo Database.

DICTIONARY OBJECT

  1. Dictionary Objects Basics
  2. Dictionary Object Basics-2
  3. Sorting Dictionary Object Keys and Items
  4. Display Records from Dictionary
  5. Add Class Objects as Dictionary Items
  6. Update Class Object Dictionary Item
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MS-Access Class-Module Tutorial Index

We are planning a series of Tutorials on Microsoft Windows Tree View Control Programming in Microsoft Access and will publish the Series in the coming weeks.

In the meantime, I thought it was appropriate to organize the earlier Tutorial Links, on Class Module and Event Handling Programming Series, of Articles on a separate page, for easy access in published order.

This is helpful for those who would like to go through the Tutorials on a gradual progressive way of learning. Those tutorials started from the Basic-level and progressed through the more advanced stage of programming levels. The learning curve should start from the base level and go up to the top to understand the changes at each level. Once you are familiar with the Object or Control, you may continue to learn further by experimenting with them on your own Programs or Projects.

After all, there is more than one way to solve a problem in Computer Programming based on the programmer’s understanding of the Language, Skill, and Experience.  

CLASS MODULE TUTORIALS

  1. MS-Access Class Module and VBA
  2. MS-Access VBA Class Object and Arrays
  3. MS-Access Base Class and Derived Objects
  4. VBA-Base Class and Derived Object-2
  5. Base Class and Derived Object Variants
  6. MS-Access Recordset and Class Module
  7. Access Class Module and Wrapper Classes
  8. Wrapper Class Functionality

COLLECTION OBJECT

  1. MS-Access and Collection Object Basics
  2. MS-Access Class Module and Collection Objects
  3. Table Records in Collection Object

DICTIONARY OBJECT

  1. Dictionary Objects Basics
  2. Dictionary Object Basics-2
  3. Sorting Dictionary Object Keys and Items
  4. Display Records from Dictionary
  5. Add Class Objects as Dictionary Items
  6. Update Class Object Dictionary Item

MS-ACCESS EVENT HANDLING TUTORIALS

  1. Withevents MS-Access Class Module
  2. Withevents and Defining Your Own Events
  3. Withevents Combo List Textbox Tab
  4. Access Form Control Arrays And Event
  5. Access Form Control Arrays And Event-2
  6. Access Form Control Arrays And Event-3
  7. Withevents in Class Module for Sub-Form
  8. Withevents in Class Module and Data
  9. Withevents and Access Report Event Sink
  10. Withevents and Report Line Hiding
  11. Withevents and Report-line Highlighting
  12. Withevents Texbox and Command Button
  13. Withevents Textbox Command Button
  14. Withevents and All Form Control Types


Download Android App MSA Guru Version of LEARN MS-ACCESS TIPS AND TRICKS, from the Google Play Store.

Download Link: MSA Guru  Size: 2.3MB

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