Android Virtual Keyboard Rectangle always zero

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: 640
    height: 480
    visible: true
    Item{
        anchors.fill: parent
        Rectangle{
            anchors.fill: parent
            color:"black"
        }

        Rectangle{
            width: parent.width
            height: 20
            color:"red"
            anchors.top:parent.top
            anchors.left:parent.left
        }
        Label {
            id: labelOut
            y: 18
            text: "Virtual Keyboard Visible: " + Qt.inputMethod.visible + " height: " + Qt.inputMethod.keyboardRectangle.height
            anchors.leftMargin: 4
            anchors.left: parent.left
            anchors.bottom: text_field.top
            color: "white"
        }

        TextField{
            id:text_field
            width: parent.width
            anchors.bottom: parent.bottom
            textColor: "grey"
        }
        Rectangle{
            height: 1
            color: "green"
            width: parent.width
            anchors.bottom: parent.bottom
        }
    }
}