treeWillExpandListener
Asks onWillChange before a node of the tree opens or closes whether it may: answering false leaves the node as it was and no expansion event follows. Requires a javax.swing.JTree target.
Return
this chain with the veto callback declared on it.
Parameters
answers for the node the event's path names; it is read when the event fires, so a fresh lambda on every recomposition registers nothing again.
See also
Asks onWillExpand before a node opens, and onWillCollapse before one closes, whether the change may happen: answering false leaves the node as it was and no expansion event follows. Requires a javax.swing.JTree target. A direction left undeclared allows the change.
Each lambda is read when its event fires, so writing a fresh one on every recomposition registers nothing again.
Declaring none at all is refused.
Return
this chain with the veto callbacks declared on it.
Parameters
answers before the node opens; false reaches the tree as the veto that keeps it closed.
answers before the node closes; false reaches the tree as the veto that keeps it open.
See also
Attaches a TreeWillExpandListener (addTreeWillExpandListener/removeTreeWillExpandListener), notified before a node opens or closes. Requires a javax.swing.JTree target.
The listener answers a change it refuses with a javax.swing.tree.ExpandVetoException, which is what a JTree reads as a veto: the node is left as it was and no expansion event follows.
Return
this chain with the veto listener declared on it.
Parameters
attached by identity, so a remembered instance stays put while a fresh one on every pass is detached and re-added.