Comment 1 Boris Bokowski 2005-11-09 17:28:03 EST

Have you tried using ITreeViewerListener?

Comment 2 venkataramana m 2005-11-10 14:37:08 EST

(In reply to comment #1)
> Have you tried using ITreeViewerListener?

Before coming to the discussion of ITreeViewerListener, some of the critical
requirements of distributed tree are as follows ...
1. ContentProvider::getChildren() should only be triggered once when + is
clicked and none when - is clicked for performance reasons. (Tree-model being
distributed in nature, cann't afford to query children not more than what is
required).

Yeah I have tried ITreeViewerListener as follows ...
public void treeCollapsed(TreeExpansionEvent event) 
{		
	ITreeNode node = (ITreeNode)(event.getElement());
	ITreeContentProvider cp = (ITreeContentProvider)fTree.getContentProvider();
	
	/* remove from viewer */
	fTree.remove(cp.getChildren(node));
				
	/* remove from model */
	node.clearChildren();
}
public void treeExpanded(TreeExpansionEvent event) {		
}

/* tree model */
abstract class TreeNode implements ITreeNode
{
	protected List fChildren;

	public List getChildren() 
	{
		if( fChildren != null )
			return fChildren;
		
		fChildren = new ArrayList();
		createChildren(fChildren);
			
		return fChildren;
	}
	
	protected abstract void createChildren(List children);
}

So what is done above is, when a tree-item collapses, treeCollapsed
event-handler clears modelchildren in viewer as well as in actual-model.
But the issue is that + sign needs to be retained for the user to be able to
again expand and see the new model children. (may be same or modified based on
modifications in the distributed model). Something like a "NEXT" button in HTML
pages on click of which distributed models are queried and shown.
So the above scenario is ruled out.

I could not get any other way of doing this.

I am attaching an example snippet illustrating above with Folder, File nodes.
(An explorer like facility where explorer should always show latest contents
without having to setup any listeners to listen to native file-system for updates.)

/* 
 * Driver code
 * -----------
 * DistributedModelTestDlg dlg = new DistributedModelTestDlg(<shell>);
 * dlg.open();
 */
class DistributedModelTestDlg extends Dialog implements ITreeViewerListener
{
	private TreeViewer fTree;
	
	public DistributedModelTestDlg(Shell parent) {
		super(parent);
	}
	
	protected Control createDialogArea(Composite parent)
	{
		Composite dlgAreaComposite = (Composite)super.createDialogArea(parent);
		createTree(dlgAreaComposite);
		return dlgAreaComposite;
	}
	
	private void createTree(Composite dlgAreaComposite)
	{
		fTree = new TreeViewer(dlgAreaComposite);
		GridData data = new GridData(GridData.FILL_BOTH);
		data.widthHint = 200;
		data.heightHint = 150;
		fTree.getControl().setLayoutData(data);
		
		fTree.setContentProvider(new TreeContentProvider());
		fTree.setLabelProvider(new TreeLabelProvider());
		
		fTree.setInput(new FolderNode(new File("C:/temp")));
		
		fTree.addTreeListener(this);
	}

public void treeCollapsed(TreeExpansionEvent event) 
{		
	ITreeNode node = (ITreeNode)(event.getElement());
	ITreeContentProvider cp = (ITreeContentProvider)fTree.getContentProvider();
	
	/* remove from viewer */
	fTree.remove(cp.getChildren(node));
				
	/* remove from model */
	node.clearChildren();
}

public void treeExpanded(TreeExpansionEvent event) {		
}
}

class TreeContentProvider implements ITreeContentProvider
{
	private static int fCounter = 0;
	
	public Object[] getChildren(Object parentElement) {
		System.out.println((fCounter++) + " getChildren");
		return ((ITreeNode)parentElement).getChildren().toArray();
	}

	public Object getParent(Object element) {
		return ((ITreeNode)element).getParent();
	}

	public boolean hasChildren(Object element) {
		return ((ITreeNode)element).hasChildren();
	}

	public Object[] getElements(Object inputElement) {
		return getChildren(inputElement);
	}

	public void dispose() {	
	}

	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
	}	
}

class TreeLabelProvider extends LabelProvider
{
	public String getText(Object element) {		
		return ((ITreeNode)element).getName();
	}
}

interface ITreeNode
{
	public String getName();
	public List getChildren();
	public boolean hasChildren();
	public ITreeNode getParent();
	public void clearChildren();
}

abstract class TreeNode implements ITreeNode
{
	protected ITreeNode fParent;
	protected List fChildren;
		
	public TreeNode(ITreeNode parent) {
		fParent = parent;
	}
	
	public boolean hasChildren() {		
		return true;
	}

	public ITreeNode getParent() {		
		return fParent;
	}
	
	public List getChildren() 
	{
		if( fChildren != null )
			return fChildren;
		
		fChildren = new ArrayList();
		createChildren(fChildren);
			
		return fChildren;
	}
	
	protected abstract void createChildren(List children);
	
	public void clearChildren() {
		fChildren = null;
	}
}

/* folder node */
class FolderNode extends TreeNode
{
	private File fFolder;
	
	public FolderNode(File folder) {
		this(null, folder);
	}
	
	public FolderNode(ITreeNode parent, File folder)
	{
		super(parent);
		fFolder = folder;
	}

	public String getName() {		
		return "FOLDER: " + fFolder.getName();
	}
	
	protected void createChildren(List children)
	{			
		File[] childFiles = fFolder.listFiles();
		for(int i=0; i<childFiles.length; i++)
		{
			File childFile = childFiles[i];
			if( childFile.isDirectory() )
				children.add(new FolderNode(this, childFile));
			else
				children.add(new FileNode(this, childFile));
		}
	}	
}

/* file node */
class FileNode extends TreeNode
{
	private File fFile;
	
	public FileNode(ITreeNode parent, File file)
	{
		super(parent);
		fFile = file;
	}
	
	public String getName() {		
		return "FILE: " + fFile.getName();
	}
	
	protected void createChildren(List children) {		
	}
	
	public boolean hasChildren() {		
		return false;
	}
}

Hope that makes a point to give the contentprovider the authority to cache or
build-afresh the children of a node. It could be just a style-bit so that
caching can be the default behavior. Whoever do not want caching
setCaching(false); may give them what they want :-)

Thanks
Venkat

Comment 3 Boris Bokowski 2009-11-26 09:53:21 EST

Hitesh is now responsible for watching bugs in the [Viewers] component area.

Comment 4 Eclipse Webmaster 2019-09-06 16:06:50 EDT

This bug hasn't had any activity in quite some time. Maybe the problem got resolved, was a duplicate of something else, or became less pressing for some reason - or maybe it's still relevant but just hasn't been looked at yet.

If you have further information on the current state of the bug, please add it. The information can be, for example, that the problem still occurs, that you still want the feature, that more information is needed, or that the bug is (for whatever reason) no longer relevant.