public void setModel(TreeModel model) {
		if (model != null) {
			if (_model != model) {
				if (_model != null) {
					_model.removeTreeDataListener(_dataListener);
				} else {
					if (_treechildren != null) _treechildren.detach();
						//don't call getItems().clear(), since it readonly
					//bug# 3095453: tree can't expand if model is set in button onClick
					smartUpdate("model", true);
				}
				clearSelection();
				_model = model;
				initDataListener();
			}
			doSort(this);
			syncModel();
		} else if (_model != null) {
			_model.removeTreeDataListener(_dataListener);
			_model = null;
			if (_treechildren != null) _treechildren.detach();
				//don't call getItems().clear(), since it readonly
			//bug# 3095453: tree can't expand if model is set in button onClick
			smartUpdate("model", false);
		}
	}