user/src/com/google/gwt/user/client/ui/TreeItem.java - gwt - Git at Google

 /*
  * Copyright 2006 Google Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License"); you may not
  * use this file except in compliance with the License. You may obtain a copy of
  * the License at
  *
  * http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  * License for the specific language governing permissions and limitations under
  * the License.
  */
 package com.google.gwt.user.client.ui;

 import com.google.gwt.user.client.DOM;
 import com.google.gwt.user.client.Element;

 import java.util.List;
 import java.util.Vector;

 /**
  * An item that can be contained within a
  * {@link com.google.gwt.user.client.ui.Tree}.
  * <p>
  * <h3>Example</h3>
  * {@example com.google.gwt.examples.TreeExample}
  * </p>
  */
 public class TreeItem extends UIObject implements HasHTML {

   /**
    * <code>Panel</code> containing the <code>Widget</code> associated with
    * the current tree item.
    */
   class ContentPanel extends SimplePanel {
     private ContentPanel(Element e) {
       super(e);
     }

     /**
      * Gets the <code>TreeItem</code> associated with this
      * <code>ContentPanel</code> for testing purposes.
      *
      * @return the tree item
      */
     TreeItem getTreeItem() {
       return TreeItem.this;
     }

     /**
      * Prevent anyone from stealing a tree item's content pane.
      *
      * @see com.google.gwt.user.client.ui.Widget#setParent(com.google.gwt.user.client.ui.Widget)
      */
     void setParent(Widget widget) {
       throw new UnsupportedOperationException(
         "Cannot directly setParent on a WidgetTreeItem's ContentPanel");
     }

     void treeSetParent(Widget widget) {
       super.setParent(widget);
     }
   }

   private Vector children = new Vector();
   private ContentPanel contentPanel;
   private Element itemTable, contentElem, imgElem, childSpanElem;
   private boolean open;
   private TreeItem parent;
   private boolean selected;
   private Object userObject;
   private Tree tree;

   /**
    * Creates an empty tree item.
    */
   public TreeItem() {
     setElement(DOM.createDiv());
     itemTable = DOM.createTable();
     contentElem = DOM.createSpan();
     childSpanElem = DOM.createSpan();
     imgElem = DOM.createImg();

     // Uses the following Element hierarchy:
     // <div (handle)>
     //  <table (itemElem)>
     //   <tr>
     //    <td><img (imgElem)/></td>
     //    <td><span (contents)/></td>
     //   </tr>
     //  </table>
     //  <span (childSpanElem)> children </span>
     // </div>

     Element tbody = DOM.createTBody(), tr = DOM.createTR();
     Element tdImg = DOM.createTD(), tdContent = DOM.createTD();
     DOM.appendChild(itemTable, tbody);
     DOM.appendChild(tbody, tr);
     DOM.appendChild(tr, tdImg);
     DOM.appendChild(tr, tdContent);
     DOM.setStyleAttribute(tdImg, "verticalAlign", "middle");
     DOM.setStyleAttribute(tdContent, "verticalAlign", "middle");

     DOM.appendChild(getElement(), itemTable);
     DOM.appendChild(getElement(), childSpanElem);
     DOM.appendChild(tdImg, imgElem);
     DOM.appendChild(tdContent, contentElem);

     DOM.setStyleAttribute(contentElem, "display", "inline");
     DOM.setStyleAttribute(getElement(), "whiteSpace", "nowrap");
     DOM.setStyleAttribute(childSpanElem, "whiteSpace", "nowrap");
     setStyleName(contentElem, "gwt-TreeItem", true);
   }

   /**
    * Constructs a tree item with the given HTML.
    *
    * @param html the item's HTML
    */
   public TreeItem(String html) {
     this();
     setHTML(html);
   }

   /**
    * Constructs a tree item with the given <code>Widget</code>.
    *
    * @param widget the item's widget
    */
   public TreeItem(Widget widget) {
     this();
     setWidget(widget);
   }

   /**
    * Adds a child tree item containing the specified text.
    *
    * @param itemText the text to be added
    * @return the item that was added
    */
   public TreeItem addItem(String itemText) {
     TreeItem ret = new TreeItem(itemText);
     addItem(ret);
     return ret;
   }

   /**
    * Adds another item as a child to this one.
    *
    * @param item the item to be added
    */

   public void addItem(TreeItem item) {
     // If this element already belongs to a tree or tree item, it should be
     // removed.
     if ((item.getParentItem() != null) || (item.getTree() != null)) {
       item.remove();
     }
     item.setTree(tree);
     item.setParentItem(this);
     children.add(item);
     DOM.setStyleAttribute(item.getElement(), "marginLeft", "16px");
     DOM.appendChild(childSpanElem, item.getElement());
     if (children.size() == 1) {
       updateState();
     }
   }

   /**
    * Adds a child tree item containing the specified widget.
    *
    * @param widget the widget to be added
    * @return the item that was added
    */
   public TreeItem addItem(Widget widget) {
     TreeItem ret = new TreeItem(widget);
     addItem(ret);
     return ret;
   }

   /**
    * Gets the child at the specified index.
    *
    * @param index the index to be retrieved
    * @return the item at that index
    */

   public TreeItem getChild(int index) {
     if ((index < 0) || (index >= children.size())) {
       return null;
     }

     return (TreeItem) children.get(index);
   }

   /**
    * Gets the number of children contained in this item.
    *
    * @return this item's child count.
    */

   public int getChildCount() {
     return children.size();
   }

   /**
    * Gets the index of the specified child item.
    *
    * @param child the child item to be found
    * @return the child's index, or <code>-1</code> if none is found
    */

   public int getChildIndex(TreeItem child) {
     return children.indexOf(child);
   }

   public String getHTML() {
     return DOM.getInnerHTML(contentElem);
   }

   /**
    * Gets this item's parent.
    *
    * @return the parent item
    */
   public TreeItem getParentItem() {
     return parent;
   }

   /**
    * Gets whether this item's children are displayed.
    *
    * @return <code>true</code> if the item is open
    */
   public boolean getState() {
     return open;
   }

   public String getText() {
     return DOM.getInnerText(contentElem);
   }

   /**
    * Gets the tree that contains this item.
    *
    * @return the containing tree
    */
   public Tree getTree() {
     return tree;
   }

   /**
    * Gets the user-defined object associated with this item.
    *
    * @return the item's user-defined object
    */
   public Object getUserObject() {
     return userObject;
   }

   /**
    * Gets the <code>Widget</code> associated with this tree item.
    *
    * @return the widget
    */
   public Widget getWidget() {
     if (contentPanel == null) {
       return null;
     }
     return contentPanel.getWidget();
   }

   /**
    * Determines whether this item is currently selected.
    *
    * @return <code>true</code> if it is selected
    */
   public boolean isSelected() {
     return selected;
   }

   /**
    * Removes this item from its tree.
    */
   public void remove() {
     if (parent != null) {
       // If this item has a parent, remove self from it.
       parent.removeItem(this);
     } else if (tree != null) {
       // If the item has no parent, but is in the Tree, it must be a top-level
       // element.
       tree.removeItem(this);
     }
   }

   /**
    * Removes one of this item's children.
    *
    * @param item the item to be removed
    */

   public void removeItem(TreeItem item) {
     if (!children.contains(item)) {
       return;
     }
     // Update Item state.
     item.setTree(null);
     item.setParentItem(null);

     children.remove(item);
     DOM.removeChild(childSpanElem, item.getElement());

     if (children.size() == 0) {
       updateState();
     }
   }

   /**
    * Removes all of this item's children.
    */
   public void removeItems() {
     while (getChildCount() > 0) {
       removeItem(getChild(0));
     }
   }

   public void setHTML(String html) {
     clearContentPanel();
     DOM.setInnerHTML(contentElem, html);
   }

   /**
    * Selects or deselects this item.
    *
    * @param selected <code>true</code> to select the item, <code>false</code>
    *          to deselect it
    */
   public void setSelected(boolean selected) {
     if (this.selected == selected) {
       return;
     }
     this.selected = selected;
     setStyleName(contentElem, "gwt-TreeItem-selected", selected);
   }

   /**
    * Sets whether this item's children are displayed.
    *
    * @param open whether the item is open
    */
   public void setState(boolean open) {
     setState(open, true);
   }

   /**
    * Sets whether this item's children are displayed.
    *
    * @param open whether the item is open
    * @param fireEvents <code>true</code> to allow open/close events to be
    *          fired
    */
   public void setState(boolean open, boolean fireEvents) {
     if (open && children.size() == 0) {
       return;
     }

     this.open = open;
     updateState();

     if (fireEvents) {
       tree.fireStateChanged(this);
     }
   }

   public void setText(String text) {
     clearContentPanel();
     DOM.setInnerText(contentElem, text);
   }

   /**
    * Sets the user-defined object associated with this item.
    *
    * @param userObj the item's user-defined object
    */
   public void setUserObject(Object userObj) {
     userObject = userObj;
   }

   /**
    * Sets the current widget. Any existing child widget will be removed.
    * @param widget Widget to set
    */
   public void setWidget(Widget widget) {
     ensureContentPanel();
     contentPanel.setWidget(widget);
   }

   /**
    * Returns the widget, if any, that should be focused on if this TreeItem is
    * selected.
    *
    * @return widget to be focused.
    */
   protected HasFocus getFocusableWidget() {
     Widget widget = getWidget();
     if (widget instanceof HasFocus) {
       return (HasFocus) widget;
     } else {
       return null;
     }
   }

   void addTreeItems(List accum) {
     for (int i = 0; i < children.size(); i++) {
       TreeItem item = (TreeItem) children.get(i);
       accum.add(item);
       item.addTreeItems(accum);
     }
   }

   Vector getChildren() {
     return children;
   }

   Element getContentElem() {
     return contentElem;
   }

   int getContentHeight() {
     return DOM.getElementPropertyInt(itemTable, "offsetHeight");
   }

   Element getImageElement() {
     return imgElem;
   }

   int getTreeTop() {
     TreeItem item = this;
     int ret = 0;

     while (item != null) {
       ret += DOM.getElementPropertyInt(item.getElement(), "offsetTop");
       item = item.getParentItem();
     }

     return ret;
   }

   String imgSrc(String img) {
     if (tree == null) {
       return img;
     }
     String src = tree.getImageBase() + img;
     return src;
   }

   void setParentItem(TreeItem parent) {
     this.parent = parent;
   }

   void setTree(Tree tree) {
     if (this.tree == tree) {
       return;
     }

     if (this.tree != null) {
       if (this.tree.getSelectedItem() == this) {
         this.tree.setSelectedItem(null);
       }

       // Detach contentPanel from old tree.
       if (contentPanel != null) {
         this.tree.disown(contentPanel);
       }
     }
     this.tree = tree;
     for (int i = 0, n = children.size(); i < n; ++i) {
       ((TreeItem) children.get(i)).setTree(tree);
     }
     updateState();
     if (tree != null) {
       if (contentPanel != null) {
         tree.adopt(contentPanel);
       }
     }
   }

   void updateState() {
     if (children.size() == 0) {
       UIObject.setVisible(childSpanElem, false);
       DOM.setElementProperty(imgElem, "src", imgSrc("tree_white.gif"));
       return;
     }

     // We must use 'display' rather than 'visibility' here,
     // or the children will always take up space.
     if (open) {
       UIObject.setVisible(childSpanElem, true);
       DOM.setElementProperty(imgElem, "src", imgSrc("tree_open.gif"));
     } else {
       UIObject.setVisible(childSpanElem, false);
       DOM.setElementProperty(imgElem, "src", imgSrc("tree_closed.gif"));
     }
   }

   void updateStateRecursive() {
     updateState();
     for (int i = 0, n = children.size(); i < n; ++i) {
       ((TreeItem) children.get(i)).updateStateRecursive();
     }
   }

   private void clearContentPanel() {
     if (contentPanel != null) {
       // Child should not be owned by anyone anymore.
       Widget child = contentPanel.getWidget();
       if (contentPanel.getWidget() != null) {
         contentPanel.remove(child);
       }

       // Tree should no longer own contentPanel.
       if (tree != null) {
         tree.disown(contentPanel);
         contentPanel = null;
       }
     }
   }

   private void ensureContentPanel() {
     if (contentPanel == null) {
       // Ensure contentElem is empty.
       DOM.setInnerHTML(contentElem, "");
       contentPanel = new ContentPanel(contentElem);
       if (getTree() != null) {
         tree.adopt(contentPanel);
       }
     }
   }

 }
	/*
	* Copyright 2006 Google Inc.
	*
	* Licensed under the Apache License, Version 2.0 (the "License"); you may not
	* use this file except in compliance with the License. You may obtain a copy of
	* the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
	* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
	* License for the specific language governing permissions and limitations under
	* the License.
	*/
	package com.google.gwt.user.client.ui;

	import com.google.gwt.user.client.DOM;
	import com.google.gwt.user.client.Element;

	import java.util.List;
	import java.util.Vector;

	/**
	* An item that can be contained within a
	* {@link com.google.gwt.user.client.ui.Tree}.
	* <p>
	* <h3>Example</h3>
	* {@example com.google.gwt.examples.TreeExample}
	* </p>
	*/
	public class TreeItem extends UIObject implements HasHTML {

	/**
	* <code>Panel</code> containing the <code>Widget</code> associated with
	* the current tree item.
	*/
	class ContentPanel extends SimplePanel {
	private ContentPanel(Element e) {
	super(e);
	}

	/**
	* Gets the <code>TreeItem</code> associated with this
	* <code>ContentPanel</code> for testing purposes.
	*
	* @return the tree item
	*/
	TreeItem getTreeItem() {
	return TreeItem.this;
	}

	/**
	* Prevent anyone from stealing a tree item's content pane.
	*
	* @see com.google.gwt.user.client.ui.Widget#setParent(com.google.gwt.user.client.ui.Widget)
	*/
	void setParent(Widget widget) {
	throw new UnsupportedOperationException(
	"Cannot directly setParent on a WidgetTreeItem's ContentPanel");
	}

	void treeSetParent(Widget widget) {
	super.setParent(widget);
	}
	}

	private Vector children = new Vector();
	private ContentPanel contentPanel;
	private Element itemTable, contentElem, imgElem, childSpanElem;
	private boolean open;
	private TreeItem parent;
	private boolean selected;
	private Object userObject;
	private Tree tree;

	/**
	* Creates an empty tree item.
	*/
	public TreeItem() {
	setElement(DOM.createDiv());
	itemTable = DOM.createTable();
	contentElem = DOM.createSpan();
	childSpanElem = DOM.createSpan();
	imgElem = DOM.createImg();

	// Uses the following Element hierarchy:
	// <div (handle)>
	// <table (itemElem)>
	// <tr>
	// <td><img (imgElem)/></td>
	// <td><span (contents)/></td>
	// </tr>
	// </table>
	// <span (childSpanElem)> children </span>
	// </div>

	Element tbody = DOM.createTBody(), tr = DOM.createTR();
	Element tdImg = DOM.createTD(), tdContent = DOM.createTD();
	DOM.appendChild(itemTable, tbody);
	DOM.appendChild(tbody, tr);
	DOM.appendChild(tr, tdImg);
	DOM.appendChild(tr, tdContent);
	DOM.setStyleAttribute(tdImg, "verticalAlign", "middle");
	DOM.setStyleAttribute(tdContent, "verticalAlign", "middle");

	DOM.appendChild(getElement(), itemTable);
	DOM.appendChild(getElement(), childSpanElem);
	DOM.appendChild(tdImg, imgElem);
	DOM.appendChild(tdContent, contentElem);

	DOM.setStyleAttribute(contentElem, "display", "inline");
	DOM.setStyleAttribute(getElement(), "whiteSpace", "nowrap");
	DOM.setStyleAttribute(childSpanElem, "whiteSpace", "nowrap");
	setStyleName(contentElem, "gwt-TreeItem", true);
	}

	/**
	* Constructs a tree item with the given HTML.
	*
	* @param html the item's HTML
	*/
	public TreeItem(String html) {
	this();
	setHTML(html);
	}

	/**
	* Constructs a tree item with the given <code>Widget</code>.
	*
	* @param widget the item's widget
	*/
	public TreeItem(Widget widget) {
	this();
	setWidget(widget);
	}

	/**
	* Adds a child tree item containing the specified text.
	*
	* @param itemText the text to be added
	* @return the item that was added
	*/
	public TreeItem addItem(String itemText) {
	TreeItem ret = new TreeItem(itemText);
	addItem(ret);
	return ret;
	}

	/**
	* Adds another item as a child to this one.
	*
	* @param item the item to be added
	*/

	public void addItem(TreeItem item) {
	// If this element already belongs to a tree or tree item, it should be
	// removed.
	if ((item.getParentItem() != null) \|\| (item.getTree() != null)) {
	item.remove();
	}
	item.setTree(tree);
	item.setParentItem(this);
	children.add(item);
	DOM.setStyleAttribute(item.getElement(), "marginLeft", "16px");
	DOM.appendChild(childSpanElem, item.getElement());
	if (children.size() == 1) {
	updateState();
	}
	}

	/**
	* Adds a child tree item containing the specified widget.
	*
	* @param widget the widget to be added
	* @return the item that was added
	*/
	public TreeItem addItem(Widget widget) {
	TreeItem ret = new TreeItem(widget);
	addItem(ret);
	return ret;
	}

	/**
	* Gets the child at the specified index.
	*
	* @param index the index to be retrieved
	* @return the item at that index
	*/

	public TreeItem getChild(int index) {
	if ((index < 0) \|\| (index >= children.size())) {
	return null;
	}

	return (TreeItem) children.get(index);
	}

	/**
	* Gets the number of children contained in this item.
	*
	* @return this item's child count.
	*/

	public int getChildCount() {
	return children.size();
	}

	/**
	* Gets the index of the specified child item.
	*
	* @param child the child item to be found
	* @return the child's index, or <code>-1</code> if none is found
	*/

	public int getChildIndex(TreeItem child) {
	return children.indexOf(child);
	}

	public String getHTML() {
	return DOM.getInnerHTML(contentElem);
	}

	/**
	* Gets this item's parent.
	*
	* @return the parent item
	*/
	public TreeItem getParentItem() {
	return parent;
	}

	/**
	* Gets whether this item's children are displayed.
	*
	* @return <code>true</code> if the item is open
	*/
	public boolean getState() {
	return open;
	}

	public String getText() {
	return DOM.getInnerText(contentElem);
	}

	/**
	* Gets the tree that contains this item.
	*
	* @return the containing tree
	*/
	public Tree getTree() {
	return tree;
	}

	/**
	* Gets the user-defined object associated with this item.
	*
	* @return the item's user-defined object
	*/
	public Object getUserObject() {
	return userObject;
	}

	/**
	* Gets the <code>Widget</code> associated with this tree item.
	*
	* @return the widget
	*/
	public Widget getWidget() {
	if (contentPanel == null) {
	return null;
	}
	return contentPanel.getWidget();
	}

	/**
	* Determines whether this item is currently selected.
	*
	* @return <code>true</code> if it is selected
	*/
	public boolean isSelected() {
	return selected;
	}

	/**
	* Removes this item from its tree.
	*/
	public void remove() {
	if (parent != null) {
	// If this item has a parent, remove self from it.
	parent.removeItem(this);
	} else if (tree != null) {
	// If the item has no parent, but is in the Tree, it must be a top-level
	// element.
	tree.removeItem(this);
	}
	}

	/**
	* Removes one of this item's children.
	*
	* @param item the item to be removed
	*/

	public void removeItem(TreeItem item) {
	if (!children.contains(item)) {
	return;
	}
	// Update Item state.
	item.setTree(null);
	item.setParentItem(null);

	children.remove(item);
	DOM.removeChild(childSpanElem, item.getElement());

	if (children.size() == 0) {
	updateState();
	}
	}

	/**
	* Removes all of this item's children.
	*/
	public void removeItems() {
	while (getChildCount() > 0) {
	removeItem(getChild(0));
	}
	}

	public void setHTML(String html) {
	clearContentPanel();
	DOM.setInnerHTML(contentElem, html);
	}

	/**
	* Selects or deselects this item.
	*
	* @param selected <code>true</code> to select the item, <code>false</code>
	* to deselect it
	*/
	public void setSelected(boolean selected) {
	if (this.selected == selected) {
	return;
	}
	this.selected = selected;
	setStyleName(contentElem, "gwt-TreeItem-selected", selected);
	}

	/**
	* Sets whether this item's children are displayed.
	*
	* @param open whether the item is open
	*/
	public void setState(boolean open) {
	setState(open, true);
	}

	/**
	* Sets whether this item's children are displayed.
	*
	* @param open whether the item is open
	* @param fireEvents <code>true</code> to allow open/close events to be
	* fired
	*/
	public void setState(boolean open, boolean fireEvents) {
	if (open && children.size() == 0) {
	return;
	}

	this.open = open;
	updateState();

	if (fireEvents) {
	tree.fireStateChanged(this);
	}
	}

	public void setText(String text) {
	clearContentPanel();
	DOM.setInnerText(contentElem, text);
	}

	/**
	* Sets the user-defined object associated with this item.
	*
	* @param userObj the item's user-defined object
	*/
	public void setUserObject(Object userObj) {
	userObject = userObj;
	}

	/**
	* Sets the current widget. Any existing child widget will be removed.
	* @param widget Widget to set
	*/
	public void setWidget(Widget widget) {
	ensureContentPanel();
	contentPanel.setWidget(widget);
	}

	/**
	* Returns the widget, if any, that should be focused on if this TreeItem is
	* selected.
	*
	* @return widget to be focused.
	*/
	protected HasFocus getFocusableWidget() {
	Widget widget = getWidget();
	if (widget instanceof HasFocus) {
	return (HasFocus) widget;
	} else {
	return null;
	}
	}

	void addTreeItems(List accum) {
	for (int i = 0; i < children.size(); i++) {
	TreeItem item = (TreeItem) children.get(i);
	accum.add(item);
	item.addTreeItems(accum);
	}
	}

	Vector getChildren() {
	return children;
	}

	Element getContentElem() {
	return contentElem;
	}

	int getContentHeight() {
	return DOM.getElementPropertyInt(itemTable, "offsetHeight");
	}

	Element getImageElement() {
	return imgElem;
	}

	int getTreeTop() {
	TreeItem item = this;
	int ret = 0;

	while (item != null) {
	ret += DOM.getElementPropertyInt(item.getElement(), "offsetTop");
	item = item.getParentItem();
	}

	return ret;
	}

	String imgSrc(String img) {
	if (tree == null) {
	return img;
	}
	String src = tree.getImageBase() + img;
	return src;
	}

	void setParentItem(TreeItem parent) {
	this.parent = parent;
	}

	void setTree(Tree tree) {
	if (this.tree == tree) {
	return;
	}

	if (this.tree != null) {
	if (this.tree.getSelectedItem() == this) {
	this.tree.setSelectedItem(null);
	}

	// Detach contentPanel from old tree.
	if (contentPanel != null) {
	this.tree.disown(contentPanel);
	}
	}
	this.tree = tree;
	for (int i = 0, n = children.size(); i < n; ++i) {
	((TreeItem) children.get(i)).setTree(tree);
	}
	updateState();
	if (tree != null) {
	if (contentPanel != null) {
	tree.adopt(contentPanel);
	}
	}
	}

	void updateState() {
	if (children.size() == 0) {
	UIObject.setVisible(childSpanElem, false);
	DOM.setElementProperty(imgElem, "src", imgSrc("tree_white.gif"));
	return;
	}

	// We must use 'display' rather than 'visibility' here,
	// or the children will always take up space.
	if (open) {
	UIObject.setVisible(childSpanElem, true);
	DOM.setElementProperty(imgElem, "src", imgSrc("tree_open.gif"));
	} else {
	UIObject.setVisible(childSpanElem, false);
	DOM.setElementProperty(imgElem, "src", imgSrc("tree_closed.gif"));
	}
	}

	void updateStateRecursive() {
	updateState();
	for (int i = 0, n = children.size(); i < n; ++i) {
	((TreeItem) children.get(i)).updateStateRecursive();
	}
	}

	private void clearContentPanel() {
	if (contentPanel != null) {
	// Child should not be owned by anyone anymore.
	Widget child = contentPanel.getWidget();
	if (contentPanel.getWidget() != null) {
	contentPanel.remove(child);
	}

	// Tree should no longer own contentPanel.
	if (tree != null) {
	tree.disown(contentPanel);
	contentPanel = null;
	}
	}
	}

	private void ensureContentPanel() {
	if (contentPanel == null) {
	// Ensure contentElem is empty.
	DOM.setInnerHTML(contentElem, "");
	contentPanel = new ContentPanel(contentElem);
	if (getTree() != null) {
	tree.adopt(contentPanel);
	}
	}
	}

	}