Combobox and Menu doesn't work in Full Screen QML

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2

ApplicationWindow {

    title: qsTr("Hello World")
    width: Screen.desktopAvailableWidth
    height: Screen.desktopAvailableHeight
    visible: true
    visibility: "FullScreen"
    menuBar: MenuBar {
        Menu {
            title: qsTr("&File")
            MenuItem {
                text: qsTr("&Open")
                onTriggered: messageDialog.show(qsTr("Open action triggered"));
            }

           MenuItem {
           text: qsTr("E&xit")
           onTriggered: Qt.quit();

            }
        }
    }
    ComboBox {

        anchors.centerIn: parent;

        width: 400

        model: [ "Banana", "Apple", "Coconut" ]

    }

}