Geertjan's Blog

  • November 21, 2008

Children.Keys for Presenting Layer Folders & Files

Geertjan Wielenga
Product Manager
Here's what's in my layer.xml:
<folder name="Words">
<file name="ajva">
<attr name="unscrambled" stringvalue="java"/>
<file name="ynamicd">
<attr name="unscrambled" stringvalue="dynamic"/>

And here's a Children.Keys class for creating a presentation layer on top of the folders and files above:

public class WordChildren extends Children.Keys<String> {
protected void addNotify() {
FileObject words = Repository.getDefault().getDefaultFileSystem().findResource("Words");
FileObject[] fos = words.getChildren();
String[] s = new String[fos.length];
for (int i = 0; i < s.length; i++) {
s[i] = fos[i].getName() + " (" + fos[i].getAttribute("unscrambled") + ")";
protected Node[] createNodes(String name) {
AbstractNode WordChildrenNode = new AbstractNode(Children.LEAF) {
public String getHtmlDisplayName() {
String normal = getDisplayName().substring(0, getDisplayName().indexOf("("));
String greyed = getDisplayName().substring(getDisplayName().indexOf("("));
return "<b>" + normal + "</b><i><font color=\\"#808080\\">" + greyed + "</font></i>";
return new Node[]{WordChildrenNode};

Here's the result, when you instantiate the above via an Explorer Manager, while an explorer view is available to it:

One of the cool things about putting your data in the layer.xml is that then other modules can add their own data to those same folders and they can even be ordered relative to each other. Then the code above will load that data, which is why there are FOUR word combinations in the screenshot above, because the NetBeans runtime container merges all the layer.xml files into one single hierarchical filesystem. Hurray for the NetBeans runtime container!

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Comments ( 4 )
  • Jesse Glick Friday, November 21, 2008

    Of course you might prefer to use Children.Keys<FileObject> and delay the calculation of the name until createNodes is called. Especially useful if you call super(true) so that nodes are not created until they become visible in a scroll viewport.

  • Varun Saturday, November 22, 2008

    You are genius!

  • JJ Sunday, November 23, 2008

    Great tip, this advice is going to save me a lot of hours! Thank you very much.

  • Adam Skalny Thursday, November 27, 2008

    Hello, nice tip. One question about it if you don't mind:

    Isn't Node#addNotify called in AWT Thread, thus it's "better" not to do an IO in there. Something like:



    protected void addNotify() {

    final SwingWorker worker = new SwingWorker<List<String>, Void>() {


    protected List<String> doInBackground() throws Exception {

    final FileObject words = Repository.getDefault().getDefaultFileSystem().findResource("Words");

    final FileObject[] fos = words.getChildren();

    final List<String> result = new ArrayList<String>(fos.length);

    for (FileObject fo : fos) {

    result.add(fo.getName() + " (" + fo.getAttribute("unscrambled") + ")");


    return result;



    protected void done() {

    try {


    } catch (Exception ex) {








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