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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 + ")" }
    }
}

設定螢幕方向為橫向，在AndroidManifest.xml檔案中:

<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
螢幕方向選項值：
1.landscape：橫屏(風景照)，顯示時寬度大於高度；
2.portrait：豎屏(肖像照)， 顯示時高度大於寬度；
3.user：使用者當前的首選方向；
4.behind：繼承Activity堆疊中當前Activity下面的那個Activity的方向；
5.sensor：由物理感應器決定顯示方向，它取決於使用者如何持有裝置，當裝置被旋轉時方向會隨之變化——在橫屏與豎屏之間；
6.nosensor：忽略物理感應器——即顯示方向與物理感應器無關，不管使用者如何旋轉裝置顯示方向都不會隨著改變(“unspecified”設定除外)；
7.unspecified：未指定，此為預設值，由Android系統自己選擇適當的方向，選擇策略視具體裝置的配置情況而定，因此不同的裝置會有不同的方向選擇；