ReferenceError: PickerPanel is not defined

[XiaoGuo, Liu]

https://developer.ubuntu.com/api/apps/qml/sdk-15.04.1/Ubuntu.Components.PickerPanel/

on the page, I just copied the code and made one example for it:

import QtQuick 2.4
import Ubuntu.Components 1.3

/*!
    \brief MainView with a Label and Button elements.
*/

MainView {
    // objectName for functional testing purposes (autopilot-qt5)
    objectName: "mainView"

    // Note! applicationName needs to match the "name" field of the click manifest
    applicationName: "pickerpanel1.liu-xiao-guo"

    width: units.gu(60)
    height: units.gu(85)

    Page {
        title: i18n.tr("pickerpanel1")

        Button {
            id: dateButton
            property date date: new Date()
            text: Qt.formatDateTime(date, "yyyy/MMMM")
            onClicked: PickerPanel.openDatePicker(dateButton, "date", "Years|Months")
        }
    }
}

When running on the phone and on Ubuntu SDK desktop kit:

qrc:///Main.qml:25: ReferenceError: PickerPanel is not defined