QML with Window.FullScreen Qt.FramelessWindowHint and transparent make the app is black screen

my qml application neet FramelessWindowHint and transparent background, so i set the like fllow:
ApplicationWindow {
visible: true
width: 800
height: 1280

visibility: Qt.platform.os == "android" ? Window.AutomaticVisibility : Window.FullScreen;
flags: Qt.FramelessWindowHint | Qt.WindowSystemMenuHint| Qt.WindowMinimizeButtonHint| Qt.Window
color: "transparent";//"black"

Rectangle

{ color: "transparent";//"#212126" anchors.fill: parent }

// others ...
}

this works on windows not normal, i want it's with transparent backgroud, but it's with black bakcground, then i try it on android, but it works normal, why???

I try the Qt example "Touch Gallery" with the same problome problem