[AccessD] Tina's Treeview example

Ok, the sample is at http://www.marlow.com/treeview.zip

 

In the database, there are three tables (to keep it simple).  tblSkills,
tblVolunteers and tblVolunteerSkills.

 

The first two tables are ID and Name (SkillID and VolunteerID).  The
third table has both id's and SkillLevel.

 

I put a few skills and two volunteers, Bob and Larry.

 

There is one form, frmVolunteerSkills.

 

It has a Combobox (Combo2...sorry, should have renamed it, but was in a
rush).  It displays the volunteers (with the bound column being the ID).

 

On the Onclick event, it runs a function 'BuildTreeView' and put's it's
value (the volunteer ID) in the intVolunteerID argument.

 

That function opens a recordset from the skills table and creates the
Nodes.

 

Ok, Before I continue, a few things to know about treeviews.  Treeviews
are a control based around nodes.  Nodes can either be Root Nodes or
Child Nodes.  You can also display check boxes or even pictures for each
node.  On top of that, node 'labels' can also be edited (if you want),
so you can even allow someone to change the text of something. If you
want an example of how you could allow your user to edit the name of a
skill from the treeview, let me know.  It takes a little bit of playing
around with a treeview and it's node objects to get used to them, but
once you do, it is a very powerful interface tool.

 

Back to BuildTreeView.  It builds a root node for each skill, and sets
it's key to "ID:x" (x being whatever ID the Skill is).  It then builds
three child nodes with the key of "ID:x:y" where y is 1 through 3 (the
skill level).

 

It then opens another recordset from the tblVolunteerSkills, based on
the VolunteerID.  It runs through that recordset 'checking' the nodes
that are applicable (the root node (skill) and the child node (skill
level), and as you can see in the code, it does this by using the values
from the table being put in the ID:x and ID:x:y format. (It also expands
any skill 'root node' that is selected already)

 

Now, the treeview itself is handling the data entry, it's doing this in
tvwSkills_NodeCheck (so it does stuff whenever you 'check' a node).
Kind of hard to write out what the logic is doing, but here's the gist,
when you click on a root node (a skill), if you don't have a skill level
selected, it really does nothing (I have commented out code where I was
trying to uncheck the node then....wasn't working, and again, this was a
quick and dirty example, there should be a way to uncheck the node, the
problem is, stepping through the code, it would uncheck it, but when the
code finished, the node rechecked itself....odd....).  But if it IS
checked, so the user is 'unchecking' a skill, it unchecks it's child
nodes (the skill levels), and deletes the appropriate record in
tblVolunteerSkills. 

 

If you check a skill level, it unchecks any other skill level (so if
skill level 1 for Cooking is checked, and the user checks skill Level 2
for cooking, Skill Level 1 for cooking unchecks itself, so it gives the
illusion of only being able to check one skill level....like a radio
button option box would...), it then tries to 'update'
tblVolunteerSkills and if no records return from that, it 'inserts' the
appropriate record.  It also 'checks' it's parent root node.  

 

If you uncheck a skill level, it unchecks it's parent, and deletes the
appropriate record from tblVolunteerSkills.

 

Like I said, this is a quick and dirty example, but it should show what
you can do with a treeview, and should also satisfy your 'click happy'
end user! ;)

 

Drew


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