HOWTO: Save the Viewing Order of Nodes in a TreeView

• Microsoft Visual FoxPro for Windows, versions 5.0, 6.0

SUMMARY

The sample BldTree.scx, located in the Vfp\Samples\Solution\Ole folder, is an example of how to use the TreeView Control. It allows you to add nodes to the TreeView and then save and restore the Nodes from a table. The algorithm that the sample uses saves all of the Nodes by index order. Because of this, it does not restore the Nodes in the same order if you added nodes using "Previous" for the Relationship. This article shows an algorithm that lets you save the Nodes in viewing order so that they can be restored in the same order.

MORE INFORMATION

This article uses the BldTree.scx as a starting point. It will have you add two new command buttons to the form: one to add Nodes to the TreeView Control and a second to save the Nodes in viewing order to a table.

The BldTree.scx can be found in the Vfp\Samples\Solution\Ole folder in Visual FoxPro 5.0. In Visual FoxPro 6.0, BldTree.scx can be found in home(2)+'solution\ole'.

For this article, set the above folder as the default by typing the following command in the Command window in Visual FoxPro 5.0:

   SET DEFAULT TO SYS(2004)+'SAMPLES\SOLUTION\OLE' 

   SET DEFAULT TO HOME(2)+'SOLUTION\OLE' 

1. Open the BldTree.scx in the Form Designer.



2. Add two new command buttons to the form. (You may have to change the size of the form to do this.)



3. Change the caption of the first new command button to "Add Previous" (without the quotes).



4. Place the following code in the Click event:

   
         o = THISFORM.oleTree
         IF !ISNULL(o.SelectedItem)
           o.Nodes.Add(o.SelectedItem.Key, 3, THISFORM.NewKey(), "previous",0)
         ENDIF 




5. Change the caption of the second new command button to "Save by View Order" (without the quotes).



6. Place the following code in the Click event:

   
          LOCAL loNodes, lcParent, lcDBFName, lcOldAlias, lcOldSafety, liIndex
          LOCAL liTmp
          #DEFINE WARNING_LOC "Continuing will destroy all data in the " + ;
             "table and create a new table with three fields." + CHR(13) + ;
             "Do you want to continue?"
          #DEFINE WARN_LOC "Warning"
   
          lcOldAlias = ALIAS()
          lcOldSafety = SET("SAFETY")
          lcDBFName = GETFILE("dbf")
   
          IF EMPTY(lcDBFName) && User chose Cancel
            RETURN
          ENDIF
   
          IF FILE(lcDBFName)
            IF THISFORM.OpenDBF(lcDBFName, .T.) AND ;
              THISFORM.VerifyTableStructure() AND ;
              MESSAGEBOX(WARNING_LOC,48+256+4,WARN_LOC) = 6
                   SET SAFETY OFF
                   ZAP
                   SET SAFETY &lcOldSafety
            ELSE
                   RETURN
            ENDIF
          ELSE
            CREATE TABLE (lcDBFName) ;
                (Key c(4), Parent c(4), Text c(60))
          ENDIF
   
          loNodes = THISFORM.oleTree.Nodes
          FOR i = 1 to loNodes.Count
             IF ISNULL(loNodes.Item(i).Parent)
               liIndex = loNodes.Item(i).FirstSibling.Index
               liTmp = liIndex
               EXIT
             ENDIF
          NEXT
   
          lcParent = "0_"  &&Root
          INSERT INTO (lcDBFName) VALUES ;
         (loNodes.Item(liIndex).key, ;
              lcParent, ;
              loNodes.Item(liIndex).Text)
   
          DO WHILE liIndex <> loNodes.Item(liTmp).LastSibling.Index
             INSERT INTO (lcDBFName) VALUES ;
                (loNodes.Item(liIndex).Next.key, ;
                lcParent, ;
                loNodes.Item(liIndex).Next.Text)
                liIndex = loNodes.Item(liIndex).Next.Index
          ENDDO
   
          FOR i = 1 TO loNodes.Count
             IF loNodes.Item(i).Children > 0
                liIndex = loNodes.Item(i).Child.Index
                liTmp = liIndex
                INSERT INTO (lcDBFName) VALUES ;
                   (loNodes.Item(liIndex).key, ;
                   loNodes.Item(liIndex).Parent.Key, ;
                   loNodes.Item(liIndex).Text)
                DO WHILE liIndex <> loNodes.Item(liTmp).LastSibling.Index
                   INSERT INTO (lcDBFName) VALUES ;
                      (loNodes.Item(liIndex).Next.key, ;
                      loNodes.Item(liIndex).Next.Parent.Key, ;
                      loNodes.Item(liIndex).Next.Text)
                      liIndex = loNodes.Item(liIndex).Next.Index
                ENDDO
             ENDIF
          NEXT
   
          USE 




7. Save the form as Vfp\Samples\Solution\Ole\Treebld2.scx



8. Run the Form and create a tree by clicking New Root twice. Select the last node in the TreeView control, and then click Add Previous.



9. Click Save DBF to save a table named OldSave.dbf. Then click Save By View Order to save a table named NewSave.dbf.



10. Click Clear, and then click Load DBF to load OldSave.dbf.



11. Repeat step 10 using NewSave.dbf.

Additional query words:

Keywords : kbcode kbActiveX kbCtrl kbVFp500 kbVFp600
Version :
Platform :
Issue type : kbhowto