Oracle JHeadstart Developer's Guide - Downloads - Oracle

Warning: The exception to the rule of "Always use a top level Data Collection
for tree selection" is when your tree starts at a detail group, and the parent
group in your application structure does not have a tree layout. In that case,
the first tree group should use a child Data Collection of the parent group for
tree selection, to prevent that the default row shown does not belong to the
selected parent.
When you run the application, search for a department that has employees (for example
'Marketing'), and click the Employees subtab. Only then the tree is shown, containing
only employees of the selected department, and already a "default" Employee row is
selected.
As you can see, the "default" employee (that is shown before any tree node was clicked)
belongs to the right department. This is because we set the Data Collection of the
Employees child group to the child usage of Departments, instead of using
EmployeesViewTreeSelect. If you would have used EmployeesViewTreeSelect, you
might see employee 'King' by default, which is not an employee of the Marketing
department.
We are faced with a dilemma when we select a Department like 'Executive'. This
department has 'King' as one of its employees, who manages employees that are not in
department 'Executive'. When we select Hartstein in the tree, we still see employee 'King'
in the Edit page. There is an error message ' JBO-25020: View row of key
oracle.jbo.Key[201 ] not found in EmployeesIterator'. Of course, the EmployeesView3
usage now includes only the employees of Human Resources, which does not include
Hartstein!
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