Scroll to item in TreeView, positionViewAtIndex seems not work

[xiaowang]

I'm trying to scroll an item to the top of treeView, and used "__listView.positionViewAtIndex(row, mode)", but it seems not work. The main qml code is as following.

TreeView {

    id: treeView
    anchors.top: header.bottom
    anchors.left: parent.left
    width: parent.width - 30
    anchors.bottom: parent.bottom

    clip: true
    style: treeViewStyle
    backgroundVisible: false
    alternatingRowColors: false
    frameVisible: false
    headerVisible: false
    horizontalScrollBarPolicy: Qt.ScrollBarAlwaysOff
    verticalScrollBarPolicy: Qt.ScrollBarAlwaysOn
    flickableItem.interactive: true

    TableViewColumn {
        title: "DevTypeName"
        role: "modelDevTypeName"
        width: parent.width
        elideMode: Text.ElideLeft
    }

    model: deviceInspectionModel

    itemDelegate: deviceDelegate

    rowDelegate: Rectangle {
        height: 46
        color: panelTheme.palette.backgroundColor
    }

    property bool isCollapse: true

    onClicked: {
        if (isCollapse) {
            console.log("expand")
            emit: treeView.expand(index);
            __listView.positionViewAtIndex(index, TreeView.Beginning )
            isCollapse = false;
        } else {
            console.log("collapse")
            emit: treeView.collapse(index);
            isCollapse = true;
        }
    }
}

Any Idea?
Thanks.

[xiaowang]

It should be used as following:
__listView.positionViewAtIndex(treeView.currentIndex.row, treeView.Beginning)

And it works when the treeview's length is enough long.