GWT: Select a TreeItem with right click - gwt

Question

I'm capturing a right click event to show a context menu. What I haven't been able to figure out, is how to make the right click actually select the TreeItem, prior to showing of context menu.
All help is appreciated.
private Tree tree = new Tree() {
#Override
public void onBrowserEvent(Event event) {
if (event.getTypeInt() == Event.ONCONTEXTMENU) {
DOM.eventPreventDefault(event);
showContextMenu(event);
}
super.onBrowserEvent(event);
}
#Override
protected void setElement(Element elem) {
super.setElement(elem);
sinkEvents(Event.ONCONTEXTMENU);
}
};

Answer 1

ONMOUSEDOWN event gets fired before ONCONTEXTMENU. Have you tried to listen for onMouseDown events, and set the selected item? Something along these lines:
#Override
public void onBrowserEvent(Event event) {
switch (DOM.eventGetType(event)) {
case Event.ONMOUSEDOWN:
if (DOM.eventGetButton(event) == Event.BUTTON_RIGHT) {
TreeItem selectedItem = findSelectedItem(event);
if (selectedItem != null) {
selectedItem.setSelected(true);
}
} else {
super.onBrowserEvent(event);
}
break;
case Event.ONCONTEXTMENU:
showContextMenu(event);
break;
default:
super.onBrowserEvent(event);
break;
}
and findSelectedItem traverses the tree looking for the selected item:
TreeItem findSelectedItem(Event e) {
return findSelectedItemRecursive(event.getClientX(), event.getClientY());
}
TreeItem findSelectedTreeItemRecursive(TreeItem root, int x, int y) {
if (null == root) {
int count = getItemCount();
for (int i = 0; i < count; i++) {
TreeItem selected = findSelectedTreeItemRecursive(getItem(i), x, y);
if (selected != null) {
return selected;
}
}
return null;
}
int count = item.getChildCount();
for (int i = 0; i < count; i++) {
TreeItem selected = findSelectedTreeItem(item.getChild(i), x, y);
if (selected != null) {
return selected;
}
}
if (x >= item.getAbsoluteLeft()
&& x <= item.getAbsoluteLeft() + item.getOffsetWidth()
&& y >= item.getAbsoluteTop()
&& y <= item.getAbsoluteTop() + item.getOffsetHeight()) {
return item;
}
return null;
}

Answer 2

You can use dedicated overloaded TreeItem :
public class MyTreeItem extends TreeItem implements ContextMenuHandler {
public SBTreeItem(SBItemTree tree, String name) {
super();
Label w = new Label(name);
w.addDomHandler(this, ContextMenuEvent.getType());
setWidget(w);
}
public void onContextMenu(ContextMenuEvent event) {
Window.alert(getSBItem().getName());
event.getNativeEvent().stopPropagation();
}
}

Answer 3

I'd just like to add a couple of links leading to issues about this:
http://code.google.com/p/google-web-toolkit/issues/detail?id=4529&q=right%20click%20selection
http://code.google.com/p/google-web-toolkit/issues/detail?id=4604&q=right%20click%20selection

Answer 4

I know this is an old question, but hopefully here's an answer that will save time for the masses hitting this page from a Google search. IMO, the best way is to use Google's own internal tree searching code -- it's a solution that scales very well with the number of elements in the tree. I
am using GWT 2.5.1.
private void initTree() {
tree = new Tree() {
#Override
public void onBrowserEvent(Event event) {
/*
* If the event is a context menu event, we want the tree item
* to also be selected.
*
* This logic must occur before the call to the superclass
* method so the selection is updated before the context menu
* logic executes. This is useful when we want to make items in
* the context menu invisible/disabled based on the selection.
*/
if (DOM.eventGetType(event) == Event.ONCONTEXTMENU) {
if (getItemCount() > 0) {
// In my use case there is only 1 top-level tree item
TreeItem root = getItem(0);
// Taken from com.google.gwt.user.client.ui.Tree.elementClicked(Element):
ArrayList<Element> chain = new ArrayList<Element>();
collectElementChain(chain, getElement(), DOM.eventGetTarget(event));
TreeItem selection = findItemByChain(chain, 0, root);
/*
* For some reason SelectionEvent will only fire if
* selection is non-null; I am firing the selection
* event manually because I want to know when there has
* been a deselection of an item in the tree.
*/
if (selection != null) {
this.setSelectedItem(selection);
} else {
SelectionEvent.fire(this, null);
}
}
}
super.onBrowserEvent(event);
}
};
tree.setAnimationEnabled(true);
}
//// BEGIN code copied from com.google.gwt.user.client.ui.Tree:
/**
* Collects parents going up the element tree, terminated at the tree root.
*/
private void collectElementChain(ArrayList<Element> chain, Element hRoot,
Element hElem) {
if ((hElem == null) || (hElem == hRoot)) {
return;
}
collectElementChain(chain, hRoot, DOM.getParent(hElem));
chain.add(hElem);
}
private TreeItem findItemByChain(ArrayList<Element> chain, int idx,
TreeItem root) {
if (idx == chain.size()) {
return root;
}
Element hCurElem = chain.get(idx);
for (int i = 0, n = root.getChildCount(); i < n; ++i) {
TreeItem child = root.getChild(i);
if (child.getElement() == hCurElem) {
TreeItem retItem = findItemByChain(chain, idx + 1,
root.getChild(i));
if (retItem == null) {
return child;
}
return retItem;
}
}
return findItemByChain(chain, idx + 1, root);
}
//// END