Bug 27670

I changed some things in TaskListener in order to solve this.
But get following exception each time I edit a task.

java.lang.IllegalArgumentException: An explored context (B) must be
within the root context (Summary).
	at
org.openide.explorer.ExplorerManager.setExploredContextAndSelection(ExplorerManager.java:299)
	at
org.openide.explorer.view.BeanTreeView.selectionChanged(BeanTreeView.java:86)
	at
org.openide.explorer.view.TreeView.callSelectionChanged(TreeView.java:613)
	at
org.openide.explorer.view.TreeView$TreePropertyListener.run(TreeView.java:874)
	at org.openide.util.Mutex.postRequest(Mutex.java:860)
	at org.openide.util.Mutex.postReadRequest(Mutex.java:349)
	at
org.openide.explorer.view.TreeView$TreePropertyListener.valueChanged(TreeView.java:844)
	at
javax.swing.tree.DefaultTreeSelectionModel.fireValueChanged(DefaultTreeSelectionModel.java:629)
	at
javax.swing.tree.DefaultTreeSelectionModel.notifyPathChange(DefaultTreeSelectionModel.java:1076)
	at
javax.swing.tree.DefaultTreeSelectionModel.setSelectionPaths(DefaultTreeSelectionModel.java:287)
	at javax.swing.JTree.setSelectionPaths(JTree.java:1194)
	at
org.openide.explorer.view.TreeTableModelAdapter$Listener.updateNodes(TreeTableModelAdapter.java:174)
[catch] at
org.openide.explorer.view.TreeTableModelAdapter$Listener.run(TreeTableModelAdapter.java:163)
	at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:178)
	at java.awt.EventQueue.dispatchEvent(EventQueue.java:448)
	at
java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197)
	at
java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
	at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
	at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)

Are you trying to set the node selection, or change the root node? If
changing the node selection, you have to be careful that the node
you're selecting is actually a descendant of the root node in effect.
This gets complicated when filter nodes are in use.
TaskNode.find(Node, Task) can help you (and to get the root to use
during the find, use view.getExplorerManager().getExploredContext(),
NOT view.getRootNode() - since that always returns the "base" root,
not the filtered one if one is in effect.

If you're trying to change the root itself, make sure that no nodes
are already selected. There's an example of this (workaround) in
TaskListView.setFilter: the first thing it does is remove the
selection (by setting the selection to an empty array) and THEN it
calls setRoot() to change the root node being explored.

By the way, your commit commented out javahelp related classpath stuff
in build.xml.  That was not intentional, right?  If you're having
problems building with that code in, your nbbuild module is out of date.

The only problem now is:
If you change a task in the filtered view the whole tree of nodes will
be recreated and the tree will be collapsed. Is there a way to remove
children from nodes to prevent this?

It colapses only if there is empty intersection between old and new 
Childen.Keys sets. 

I doubt that a usertask should disappear as result of property
editing. But I can imagine task disappearing while moving (gesture
that I'm done with it) to next task i.e. leaving current 'record'.

already fixed.
If a user marks for example a task as completed and the current filter
does not accept those tasks the task will disappear from the list.

NB 4.1 is out