BC4J ViewLink Combobox model binding

Question

I am having difficulty with a jclient panel I have built, using a combobox model binding.
I have a screen where one combobox contents depend upon the status of a previous selection.
An example of this would be to have an employee table with columns:
employee - the reference to this row
level - a numeric representation of the employee level
reports_to - a self referential column detailing the manager
Based upon the selection (via a combobox) of the level, the reports_to selection should be limited to employees of higher level.
I achieved this through the use of a view link within the business components, amending the view link sql statement to use 'greater than' rather than 'equals'.
This performs perfectly within the business components tester, selecting the correct data for each employee.
BUT, when using a combobox model binding to select both items of data there seems to be a bug when navigating through the data.
The second record you view within the jclient panel has no display text within the combobox. The third record is ok but the fourth record appears to do the same. Further records seem ok, but this does not happen if you navigate through the rows backwards!
If you navigate to the end data row first to avoid hitting the second record the same happens, but then all records are fine when navigating back!
This seems very bizarre and could only be a bug within the BC4J framework (i hope).
An example can be mailed if the jdev team cannot replicate, or more info given if required.
Thanks in advance.

Answer 1

We have had this problem for some time but now have a solution.
Our problem is that the ComboBox is bound to two (linked) Views, one for its regular value and one for the LOV, which I shall call ViewMain and ViewLov respectively.
When the ViewMain is navigated, the JUComboBoxBinding is notified as for any control binding. Also, the ViewLov gets navigation events (rangeRefreshed I think) due to the link which are also passed to the JUComboBoxBinding. The order of these notifications seems to be outside my control.
If the ViewLov norification occurs first and the old value isn't in the new LOV, then the selected index is set to -1. When the ViewMain notification arrives, the situation is resolved as the new value is in the LOV.
However, if the ViewMain notification arrives first and the new value isn't in the old LOV, the selected item index becomes -1. This isn't resolved when the ViewLov notification arrives.
Our solution is to extract the source of JUComboBoxBinding and modify
protected void setupListItems(boolean clean, boolean keepSelectedIndex)
At the end we add the following code:
// When LOV changes, need to update for bound attribute's current value.
Row lRow = getRowIterator().getCurrentRow();
if (lRow != null)
{   updateValuesFromRow(lRow);
My understanding of the internal machinations of BC4J isn't thorough enough to say if this is a "correct" solution or not, but it seems to work.
HTH
Tony.