Error with the example Qt for Android project

[Qt_crazyer]

I want to try Qt for Android. After I have built the Android kits, I open an example project, but it has error.

import QtQuick.Controls.Material 2.1
import QtQuick.Controls.Universal 2.1

error: QML module not found. (QtQuick.Controls.Material)
error: QML module not found. (QtQuick.Controls.Universal)

I am using Qt creator 5.9.1 on windows10. And I don't know much about QML.
How should I solve it?
Thanks in advance.