Step 4 Fill the Tree View on Demand

Step 4. Fill the Tree View on Demand

VFW060 – Using a Tree View

The tree view is currently loaded with all department, section and employee data initially. Clearly this is an approach which will work well for a small amount of data. For your own applications, it is much more likely that you will need to populate the tree view "on demand". Your logic would add all records to level one, and then add to level two and three when a level is expanded (by click on the + next to that item).

In this step you will change your logic so that the tree view is populated on demand.

1.  In the Design view, select the tree view and change its ManageChildren property to true.

     The help for this property (see F2 Features help) will inform you:

     ManageChildren controls what happens when a tree item is collapsed.

     The ManageChildren property controls whether child items are automatically deleted when a tree item is collapsed. It will typically be used when the children are loaded during an ItemExpanding event. It can be set to True or False.

2.  Create an ItemExpanding event handling routine for the tree view.

3.  Cut and paste the Select sections and select employees logic from the from the Initialize event into the Tree view ItemExpanding event handling routine.

     The form Initialize logic should now only add department data to the tree initially.

     Your form Initialize should look like the following:

Evtroutine Handling(#com_owner.Initialize)
Set Com(#com_owner) Caption(*component_desc)
Clr_List Named(#TRVW_1)
Select Fields(#DEPTMENT #DEPTDESC) From_File(deptab)
Add_Entry To_List(#TRVW_1)
Endselect
Endroutine

4.  Like the ItemGotSelection event routine, the ItemExpanding event will need to perform the action required based on the level selected. Add the required logic re-using the code pasted from the form Initialize routine.

• Assign TRVW_1.currentItem.Level to STD_NUM

• Within a Case loop for STD_NUM:

• For Level 1, select from the sections file for this department

• For Level 2, select from the employees file for this department / section.

• For Level 3, no action required.

     Your code should now look like the following:

Evtroutine Handling(#TRVW_1.ItemExpanding) Options(*NOCLEARMESSAGES *NOCLEARERRORS)
#std_num := #TRVW_1.currentItem.level
Case (#std_num)
When (= 1)
Select Fields(#SECTION #SECDESC) From_File(sectab) With_Key(#DEPTMENT)
Add_Entry To_List(#TRVW_1)
Endselect
When (= 2)
Select Fields(#EMPNO #SURNAME #GIVENAME) From_File(pslmst1) With_Key(#DEPTMENT #SECTION)
#fullname := #SURNAME + ', ' + #GIVENAME
Add_Entry To_List(#TRVW_1)
Endselect
When (= 3)
* no action required
Endcase
Endroutine

5.  Compile your form and test it. From an end user perspective it should work exactly the same as before.