How to use a Tree Expansion Listener in Java?

[Rob Dizzle]

Hi friends,
I am posting this query for the first time on this forum. So please don't overlook it. I am trying to use tree expansion listener because I have used the Tree. Now I need to react when a branch becomes expanded or collapsed, so I want to use that listener. Please help me by telling how to use a Tree Expansion Listener in Java.?? Expecting some help soon as possible.!!

[absolute55]

There are some scenarios when you need to react when a branch becomes expanded or collapsed, at such times using tree expansion listener would be useful. But before going for the listener, you must know better about the using the tree in Java. You can display hierarchical data by using the JTree class. You will get more information about the writing Trees in Java on the following link :
How to use Trees in Java?
Hope that it helps you.!!!

[Zecho]

I think that you should know more about the methods that are used by the Tree Expansion Listener to clear your concepts. You should keep in mind that TreeExpansionListener has no adapter class. The following are the methods used by the TreeExpansionListener Interface :

• treeCollapsed(TreeExpansionEvent) - This method is called just after a tree node collapses.
• treeExpanded(TreeExpansionEvent) - After a tree node expands, this method is called.

[Deabelos]

Before doing the coding, you should also know the methods that are used by the TreeExpansionEvent API. The following are the methopds of the same :

• Object getSource() - This method returns the object that fired the event.
• TreePath getPath() - This method returns a TreePath object that identifies each node from the root of the tree. This also returns the collapsed or expanded node.

Hope you will get some help from this.!!

[kyosang]

I have provided you with following code that shows how the program handles expansion events :

public class TreeExpandTrial ... {
    ...
    void saySomething(String eventDescription, TreeExpansionEvent te) {
        textArea.append(eventDescription + "; "
                        + "path = " + te.getPath()
                        + newline);
    }

    class DemoArea ... implements TreeExpansionListener {
        ...
        public DemoArea() {
            ...
            tree.addTreeExpansionListener(this);
            ...
        }
        ...
        public void treeExpanded(TreeExpansionEvent te) {
            saySomething("Tree-expanded event detected", te);
        }

        public void treeCollapsed(TreeExpansionEvent te) {
            saySomething("Tree-collapsed event detected", te);
        }
    }
}