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NullpointerException after calling fireEvent(...) in TreeModel

asked 2011-07-06 17:32:29 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

Hello everyone,

I am currently trying to rename a Treeitem in my Tree component, like this:

treeitem.setLabel("foo");
Tree tree = treeitem.getTree();
if (tree != null) {
	TreeModel model = tree.getModel();
	if (model instanceof AdvancedTreeModel) {
		AdvancedTreeModel amodel = (AdvancedTreeModel) model;
		TreeNode node = renamedFolder.getNode();
		amodel.refreshNode(node);
	}
}

The AdvancedTreeModel looks like this:

public class AdvancedTreeModel extends DefaultTreeModel {
	private static final long	serialVersionUID	= 129891927119818367L;

	/**
	 * Refreshes the given node
	 * 
	 * @param node
	 *            The node to refresh
	 */
	public void refreshNode(TreeNode node) {
		if (node != null) {
			TreeNode parent = node.getParent();
			if (parent != null) {
				int index = parent.getIndex(node);
				if (index >= 0) {
					// This causes the NullPointerException!
					fireEvent(parent, index, index, TreeDataEvent.CONTENTS_CHANGED);
				}
			}
		}
	}
}

Unfortunately, this gives me a NullPointerException:

org.zkoss.zk.ui.UiException: Not a child: <Treeitem null>
	at org.zkoss.zul.Tree.addItemToSelection(Tree.java:845)
	at org.zkoss.zul.Tree$Renderer.render(Tree.java:1684)
	at org.zkoss.zul.Tree$Renderer.access$800(Tree.java:1664)
	at org.zkoss.zul.Tree.renderChangedItem(Tree.java:1851)
	at org.zkoss.zul.Tree.onTreeDataContentChange(Tree.java:1405)
	at org.zkoss.zul.Tree.onTreeDataChange(Tree.java:1337)
	at org.zkoss.zul.Tree.access$400(Tree.java:95)
	at org.zkoss.zul.Tree$4.onChange(Tree.java:1463)
	at org.zkoss.zul.AbstractTreeModel.fireEvent(AbstractTreeModel.java:77)
	at com.smampi.web.view.client.mailaccount.tree.AdvancedTreeModel.refreshNode(AdvancedTreeModel.java:93)

What am I doing wrong?

(Obviously, a Treeitem reference seems to be null but which one? I checked on both (the Treeitem for the current node as well as its parent) and they're both not null..

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answered 2011-07-07 08:43:58 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

Noone's got an idea? :-(

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answered 2011-07-07 08:50:31 +0800

marcelodecampos gravatar image marcelodecampos
183

Are you using a renderer? Could you show it?

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answered 2011-07-07 10:27:34 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

Yes, I do. It looks like this:

@Override
public void afterCompose() {
	super.afterCompose();
	
	tree_mailaccounts.setItemRenderer(new TreeitemRenderer() {
		@Override
		public void render(Treeitem item, Object obj) throws Exception {
			item.setValue(obj);

			Treerow treerow = item.getTreerow();
			if (treerow == null) {
				treerow = new Treerow();
				treerow.setParent(item);
			}
			treerow.setHflex("min");
			item.setHflex("min");

			// Registers an "onOpen" event for this item
			setTreeitemOnOpenEventListener(item);

			// Enable drag & drop
			treerow.setDroppable("true");
			treerow.setDraggable("true");

			// Set listener for drag and drop event
			setTreeRowOnDropListener(treerow);

			// Render the label of the tree item
			try {
				renderTreeitemLabel(item);
			} catch (Exception e) {
				handleException(e, false, null, null);
			}
		}

		/*
		 * Sets an event listener for the onOpen event on treeitems
		 */
		private void setTreeitemOnOpenEventListener(Treeitem item) {
			item.addEventListener(Events.ON_OPEN,
				new TreeitemOnOpenEventListener(item));
		}
	});
}

public int renderTreeitemLabel(Treeitem item) {

	if (item == null) {
		return -1;
	}

	Object obj = item.getValue();

	int count = -1;
	
	if (obj instanceof TreeNode) {
		TreeNode node = (TreeNode) obj;
		Object data = node.getData();
		boolean connectionWorks = true;
		CachedFolder cachedFolder = null;
		
		if (data instanceof MailAccount || data instanceof CachedFolder) {
			String label = "";
			MailAccount account = null;
			if (data instanceof MailAccount) {
				account = (MailAccount) data;
				account.setTreeitem(item);
				item.setContext(mpop_tree_mail_account);

				handleTreeitemOpenStatus(item, account);

				try {
					count = account.getNumberOfUnreadMessages(true);
				} catch (Exception e) {
					count = 0;
				}

				if (count > 0) {
					label = account.toString() + " (" + count + ")";
				} else {
					label = account.toString();
				}
				connectionWorks = account.getIncomingServer().connectionWorks();
			} else if (data instanceof CachedFolder) {
				cachedFolder = (CachedFolder) data;
				cachedFolder.setTreeitem(item);

				boolean useCache = true;
				count = cachedFolder.getNumOfUnreadMessages(useCache, true);
				label = cachedFolder.getName(useCache, true);

				// Saves if the item was open or closed
				handleTreeitemOpenStatus(item, cachedFolder);

				if (cachedFolder.isInbox(useCache)) {
					item.setContext(mpop_tree_folder_inbox);
				} else {
					item.setContext(mpop_tree_folder);
				}
			}

			Treerow tr = item.getTreerow();
			Treecell cell = null;

			if (tr == null) {
				tr = new Treerow();
				tr.setParent(item);
			}

			if (tr.getChildren().size() > 0) {
				cell = (Treecell) tr.getChildren().get(0);
				cell.setLabel(label);
			} else {
				cell = new Treecell(label);
				cell.setParent(tr);
			}

			// If unread messages exist, make the tree item bold
			if (count > 0) {
				cell.setTooltiptext(count + " " + "unread messages");
				cell.setStyle("font-weight: bold");
			} else {
				cell.setTooltiptext(null);
				cell.setStyle("font-weight: normal");
			}

			if (account != null) {
				account.setTreecell(cell);
			}

			if (cachedFolder != null) {
				cachedFolder.setTreecell(cell);
				if (cachedFolder.isInbox(true)) {
					cachedFolder.setFolderType(FolderType.INBOX);
				}
				cachedFolder.refreshIcon();
			}

			if (!connectionWorks) {
				cell.setStyle("text-decoration: line-through; color: #999;");
				cell.setTooltiptext("Connection to server failed");
			}

			// Remove hand cursor
			cell.setStyle(cell.getStyle() + "; cursor: default;");
		}
	}
	return count;
}

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answered 2011-07-11 04:17:11 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

Still cannot find the cause for the NullPointerException.. :-(

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answered 2011-07-11 06:29:39 +0800

matthewgo gravatar image matthewgo
375

Hi valmar,

maybe the treeitem is not attached to tree when you fireevent ?
can you provide a sample code to reproduce the issue?

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answered 2011-07-11 06:53:19 +0800

gsim gravatar image gsim
81

It seems that one of your treeitems has a bad reference to another tree
did you check if all treeitems passed to the render method in the TreeitemRenderer are correctly associated to your tree?

From org.zkoss.zulTree:

public void addItemToSelection(Treeitem item) {
	if (item.getTree() != this)
		throw new UiException("Not a child: "+item);

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answered 2011-07-11 08:21:20 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

updated 2011-07-11 08:22:10 +0800

gsim wrote:

It seems that one of your treeitems has a bad reference to another tree
did you check if all treeitems passed to the render method in the TreeitemRenderer are correctly associated to your tree?

Hm, I added the following to the item renderer. No effect :-(
Note: The tree I am working with is the only tree in the whole application. So it's unlikely that there an item point at a different tree.

if (item.getTree() != tree_mailaccounts) {
	try {
		// Gets never called
		Messagebox.show("Error, wrong Tree!");
	} catch (InterruptedException e) {
		e.printStackTrace();
	}
}

matthewgo wrote:

maybe the treeitem is not attached to tree when you fireevent ?
can you provide a sample code to reproduce the issue?

How could I check if the item is attached to the tree or not?
Regarding the sample code: I'll see if I can setup a small test project which reproduces the issue.

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answered 2011-07-11 09:00:32 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

updated 2011-07-11 09:02:39 +0800

I tried to create a project which reproduces the issue.

Unfortunately, I don't get the exception here. Instead, simply nothing happens when you click the button on the UI.

I think something smells really fishy here. Probably I am doing something completely the wrong way. Maybe some of you sees the error?

Download: http://dl.dropbox.com/u/17844821/zeug/TreeError.zip

(The app displays a tree with two items. One of these items is called "foo". After clicking the button below the tree, this node should be renamed.)

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answered 2011-07-11 10:06:21 +0800

gsim gravatar image gsim
81

You should always work with the model when changing data of the tree.

It makes no sense to store references of a treeitem, as they will be outdated when zk performs another request and render the ui again.

Just change the node in the model calling setData. This will trigger a TreeDataEvent on the model rendering again your tree and updating the ui.

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answered 2011-07-11 12:45:58 +0800

valmar gravatar image valmar
925 2 13
http://www.timo-ernst.net

updated 2011-07-11 13:10:12 +0800

Hmm... the "demo" in TreeError.zip works now after simply calling setData(...) on the node but in my "real" project I still get the same old exception after doing the change.

org.zkoss.zk.ui.UiException: Not a child: <Treeitem null>
	at org.zkoss.zul.Tree.addItemToSelection(Tree.java:845)
	at org.zkoss.zul.Tree$Renderer.render(Tree.java:1684)
	at org.zkoss.zul.Tree$Renderer.access$800(Tree.java:1664)
	at org.zkoss.zul.Tree.renderChangedItem(Tree.java:1851)
	at org.zkoss.zul.Tree.onTreeDataContentChange(Tree.java:1405)
	at org.zkoss.zul.Tree.onTreeDataChange(Tree.java:1337)
	at org.zkoss.zul.Tree.access$400(Tree.java:95)
	at org.zkoss.zul.Tree$4.onChange(Tree.java:1463)
	at org.zkoss.zul.AbstractTreeModel.fireEvent(AbstractTreeModel.java:77)
	at org.zkoss.zul.DefaultTreeNode.setData(DefaultTreeNode.java:119)

So, I guess the mistake is somewhere in my code but I just cannot find it..


Gsim, One thing I noticed about the code you posted:

public void addItemToSelection(Treeitem item) {
	if (item.getTree() != this)
		throw new UiException("Not a child: "+item);

The exception says: Not a child: <Treeitem null>

What exactly is the term "null" refering to at this point?
The item itself cannot be null. So, what's null then?

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Asked: 2011-07-06 17:32:29 +0800

Seen: 748 times

Last updated: Feb 14 '12

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