QtQuick获取屏幕信息

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import QtQuick 2.3
import QtQuick.Window 2.1

Item {
    id: root
    width: 400
    height: propertyGrid.implicitHeight + 16

    function orientationToString(o) {
        switch (o) {
        case Qt.PrimaryOrientation:
            return "primary";
        case Qt.PortraitOrientation:
            return "portrait";
        case Qt.LandscapeOrientation:
            return "landscape";
        case Qt.InvertedPortraitOrientation:
            return "inverted portrait";
        case Qt.InvertedLandscapeOrientation:
            return "inverted landscape";
        }
        return "unknown";
    }

    Grid {
        id: propertyGrid
        columns: 2
        spacing: 8
        x: spacing
        y: spacing

        Text {
            text: "Screen \"" + Screen.name + "\":"
            font.bold: true
        }
        Item { width: 1; height: 1 } // spacer

        Text { text: "dimensions" }
        Text { text: Screen.width + "x" + Screen.height }

        Text { text: "pixel density" }
        Text { text: Screen.pixelDensity.toFixed(2) + " dots/mm (" + (Screen.pixelDensity * 25.4).toFixed(2) + " dots/inch)" }

        Text { text: "logical pixel density" }
        Text { text: Screen.logicalPixelDensity.toFixed(2) + " dots/mm (" + (Screen.logicalPixelDensity * 25.4).toFixed(2) + " dots/inch)" }

        Text { text: "device pixel ratio" }
        Text { text: Screen.devicePixelRatio.toFixed(2) }

        Text { text: "available virtual desktop" }
        Text { text: Screen.desktopAvailableWidth + "x" + Screen.desktopAvailableHeight }

        Text { text: "orientation" }
        Text { text: orientationToString(Screen.orientation) + " (" + Screen.orientation + ")" }

        Text { text: "primary orientation" }
        Text { text: orientationToString(Screen.primaryOrientation) + " (" + Screen.primaryOrientation + ")" }
    }
}

http://doc.qt.io/qt-5/qtquick-window-screeninfo-qml.html

设置屏幕方向为横向，在AndroidManifest.xml文件中:

<activity android:screenOrientation="portrait" ... 

http://stackoverflow.com/questions/20774498/qml-screen-orientation-lock
https://forum.qt.io/topic/49120/how-to-lock-screen-orientation-qml-android-ios/3
屏幕方向选项值：
1.landscape：横屏(风景照)，显示时宽度大于高度；
2.portrait：竖屏(肖像照)， 显示时高度大于宽度；
3.user：用户当前的首选方向；
4.behind：继承Activity堆栈中当前Activity下面的那个Activity的方向；
5.sensor：由物理感应器决定显示方向，它取决于用户如何持有设备，当设备被旋转时方向会随之变化——在横屏与竖屏之间；
6.nosensor：忽略物理感应器——即显示方向与物理感应器无关，不管用户如何旋转设备显示方向都不会随着改变(“unspecified”设置除外)；
7.unspecified：未指定，此为默认值，由Android系统自己选择适当的方向，选择策略视具体设备的配置情况而定，因此不同的设备会有不同的方向选择；

其他信息：
为app添加收费功能:
http://blog.qt.io/blog/2013/12/12/implementing-in-app-purchase-on-android/