qt qml scrollbar 移动APP风格的滚动轴

依附于Flickable组件的滚动轴
    自动放置在恰当位置
    拖动时显示，不动时消失
Lisence: MIT 请保留此声明
Author: surfsky.cnblogs.com 2014-12

【先看效果】

【下载】

http://download.csdn.net/detail/surfsky/8426563

【核心代码】

ScrollBar {
    id: root
    opacity: 0
    orientation: Qt.Vertical

    // 绑定到Flickable组件
    property Flickable target : Flickable{}

    // 位置
     orientation==Qt.Vertical ? 10 : target.width-10
    height: orientation==Qt.Vertical ? target.height-10 : 10
    anchors.right: orientation==Qt.Vertical ? target.right : undefined
    anchors.bottom: orientation==Qt.Vertical ? undefined : target.bottom

    // 滚动
    position: orientation==Qt.Vertical ? target.visibleArea.yPosition   : target.visibleArea.xPosition
    pageSize: orientation==Qt.Vertical ? target.visibleArea.heightRatio : target.visibleArea.widthRatio


    // 移动时显隐滚动轴
    Connections{
        target: root.target
        onMovingVerticallyChanged: {
            if (target.movingVertically)
                fadeIn.start();
            else
                fadeOut.start();
        }
        onMovingHorizontallyChanged: {
            if (target.movingHorizontally)
                fadeIn.start();
            else
                fadeOut.start();
        }
    }
    NumberAnimation { id:fadeIn;  target: root; properties: "opacity"; duration: 400; from:0; to:1 }
    NumberAnimation { id:fadeOut; target: root; properties: "opacity"; duration: 400; from:1; to:0 }
}

【调用示例】

    FlickableScrollBar {
        target: view
        orientation: Qt.Vertical
    }