ReferenceError error after calling TreeView.forceLayout in Qt 6.5

[A Former User]

I have a tree view in a popup. The code looks like this:

Popup {
    id: root
    
    TreeView {
        id: treeView
        ......

        model: myModel
        delegate: TreeViewDelegate {
            indicator: Image {
                ......
                MouseArea {
                    .....
                    onClicked: {
                        if (myModel.canFetchMore(index)) {
                            myModel.fetchMore(index);
                        }
                        treeView.expand(row);
                        treeView.forceLayout();
                        // Got **ReferenceError: treeViewItem is not defined** in the next line
                        treeView.positionViewAtRow(row, TreeView.AlignTop);
            
                        // If I call some property in root, it will report **ReferenceError: root is not defined**
                     }
                }
            }
        }
    }
}

Does anyone know the reason of the error?
Thanks in advance.