c++ - QML Coverflow 非常慢

Question

我想为非触摸应用程序实现 CoverFlow。就像是: https://www.youtube.com/watch?v=0MT58xIzp5c

我已经掌握了基础知识，但有两个问题:

1. 与轻弹相比，使用鼠标滚轮非常慢，尤其是当我快速滚动时。如何让 incrementCurrentIndex() 和 decrementCurrentIndex() 函数像轻弹一样快？
2. 从一个项目滚动到下一个项目时，我可以看到一秒钟的白色背景(项目不会同时移动)。有没有办法解决这个问题？

这是我的代码的一个工作示例:

import QtQuick 2.4
import QtQuick.Window 2.2

Window {
    visible: true
    width: 1280
    height: 800
    MouseArea {
        //the mouse events will be replaced with c++ events later
        anchors.fill: parent
        onWheel: {
            if (wheel.angleDelta.y < 0)
            {
                view.incrementCurrentIndex()
            }
            else if (wheel.angleDelta.y > 0)
            {
                view.decrementCurrentIndex()
            }
        }
    }

    PathView {
        id: view
        property int itemAngle: 40.0
        property int itemSize: width/3.5

        anchors.fill: parent
        pathItemCount: 10
        preferredHighlightBegin: 0.5
        preferredHighlightEnd: 0.5
        interactive: true
        model: [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
        delegate: viewDelegate
        path: Path {
            startX: 0
            startY: height / 2
            PathPercent { value: 0.0 }
            PathAttribute { name: "z"; value: 0 }
            PathAttribute { name: "angle"; value: view.itemAngle }
            PathAttribute { name: "origin"; value: 0 }


            PathLine {x: view.width*0.4; y: view.height / 2}
            PathPercent { value: 0.48 }
            PathAttribute { name: "angle"; value: view.itemAngle }
            PathAttribute { name: "origin"; value: 0 }
            PathAttribute { name: "z"; value: 10 }


            PathLine { relativeX: 0; relativeY: 0 }
            PathAttribute { name: "angle"; value: 0.0 }
            PathAttribute { name: "origin"; value: 0 }
            PathAttribute { name: "z"; value: 10 }


            PathLine {x: view.width*0.6; y: view.height / 2}
            PathPercent { value: 0.52 }
            PathAttribute { name: "angle"; value: 0.0 }
            PathAttribute { name: "origin"; value: 0 }
            PathAttribute { name: "z"; value: 10 }


            PathLine { relativeX: 0; relativeY: 0 }
            PathAttribute { name: "angle"; value: -view.itemAngle }
            PathAttribute { name: "origin"; value: view.itemSize }
            PathAttribute { name: "z"; value: 10 }


            PathLine {x: view.width; y: view.height / 2}
            PathPercent { value: 1 }
            PathAttribute { name: "angle"; value: -view.itemAngle }
            PathAttribute { name: "origin"; value: view.itemSize }
            PathAttribute { name: "z"; value: 0 }
        }
    }

    Component {
        id: viewDelegate
        Rectangle {
            id: flipItem
            width: view.itemSize
            height: view.height
            color: "white"
            z: PathView.z

            property var rotationAngle: PathView.angle
            property var rotationOrigin: PathView.origin

            transform:
                Rotation {
                id: rot
                axis { x: 0; y: 1; z: 0 }
                angle: rotationAngle
                origin.x: rotationOrigin
                origin.y: width
            }


            Rectangle {
                border.color: "black"
                border.width: 2
                color: (index%2 === 0) ? "yellow" : "royalblue"
                anchors.top: flipItem.top
                anchors.topMargin: 100
                anchors.left: flipItem.left
                anchors.right: flipItem.right
                width: flipItem.width
                height: flipItem.height*0.55
                smooth: true
                antialiasing: true
                Text {
                    text: model.modelData
                    color: "gray"
                    font.pixelSize: 30
                    font.bold: true
                    anchors.centerIn: parent
                }
            }
        }
    }
}

我想要实现的是从 C++ 端控制滚动(使用事件)并使其与用鼠标轻弹一样快。

Answer 1

这是您的代码，(我希望)按您预期的方式工作:

import QtQuick 2.4
import QtQuick.Window 2.2

Window {
    visible: true
    width: 1280
    height: 800
    MouseArea {
        //the mouse events will be replaced with c++ events later
        anchors.fill: parent
        onWheel: {
            if (wheel.angleDelta.y < 0)
            {
                if (scrollViewAnimation.running) {
                    scrollViewAnimation.stop()
                    scrollViewAnimation.to--
                    scrollViewAnimation.start()
                }
                else {
                    scrollViewAnimation.to = Math.round(view.offset - 1)
                    scrollViewAnimation.start()
                }
            }
            else if (wheel.angleDelta.y > 0)
            {
                if (scrollViewAnimation.running) {
                    scrollViewAnimation.stop()
                    scrollViewAnimation.to++
                    scrollViewAnimation.start()
                }
                else {
                    scrollViewAnimation.to = Math.round(view.offset + 1)
                    scrollViewAnimation.start()
                }
            }
        }
    }

    PathView {
        id: view
        property int itemAngle: 40.0
        property int itemSize: width/3.5

        anchors.fill: parent
        pathItemCount: 10
        preferredHighlightBegin: 0.5
        preferredHighlightEnd: 0.5
        interactive: true
        model: [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]
        delegate: viewDelegate

        onDragStarted: {
            scrollViewAnimation.stop()
        }

        NumberAnimation on offset {
            id: scrollViewAnimation
            duration: 250
            easing.type: Easing.InOutQuad
        }

        path: Path {
            startX: 0
            startY: height / 2
            PathPercent { value: 0.0 }
            PathAttribute { name: "z"; value: 0 }
            PathAttribute { name: "angle"; value: view.itemAngle }
            PathAttribute { name: "origin"; value: 0 }


            PathLine {x: view.width*0.4; y: view.height / 2}
            PathPercent { value: 0.45 }
            PathAttribute { name: "angle"; value: view.itemAngle }
            PathAttribute { name: "origin"; value: 0 }
            PathAttribute { name: "z"; value: 10 }


            PathLine { relativeX: 0; relativeY: 0 }
            PathAttribute { name: "angle"; value: 0.0 }
            PathAttribute { name: "origin"; value: 0 }
            PathAttribute { name: "z"; value: 10 }


            PathLine {x: view.width*0.6; y: view.height / 2}
            PathPercent { value: 0.55 }
            PathAttribute { name: "angle"; value: 0.0 }
            PathAttribute { name: "origin"; value: 0 }
            PathAttribute { name: "z"; value: 10 }


            PathLine { relativeX: 0; relativeY: 0 }
            PathAttribute { name: "angle"; value: -view.itemAngle }
            PathAttribute { name: "origin"; value: view.itemSize }
            PathAttribute { name: "z"; value: 10 }


            PathLine {x: view.width; y: view.height / 2}
            PathPercent { value: 1 }
            PathAttribute { name: "angle"; value: -view.itemAngle }
            PathAttribute { name: "origin"; value: view.itemSize }
            PathAttribute { name: "z"; value: 0 }
        }
    }

    Component {
        id: viewDelegate
        Rectangle {
            id: flipItem
            width: view.itemSize
            height: view.height
            color: "white"
            z: PathView.z

            property var rotationAngle: PathView.angle
            property var rotationOrigin: PathView.origin

            transform:
                Rotation {
                id: rot
                axis { x: 0; y: 1; z: 0 }
                angle: rotationAngle
                origin.x: rotationOrigin
                origin.y: width
            }


            Rectangle {
                border.color: "black"
                border.width: 2
                color: (index%2 === 0) ? "yellow" : "royalblue"
                anchors.top: flipItem.top
                anchors.topMargin: 100
                anchors.left: flipItem.left
                anchors.right: flipItem.right
                width: flipItem.width
                height: flipItem.height*0.55
                smooth: true
                antialiasing: true
                Text {
                    text: model.modelData
                    color: "gray"
                    font.pixelSize: 30
                    font.bold: true
                    anchors.centerIn: parent
                }
            }
        }
    }
}

1. 滚动的问题在于函数 PathView.incrementCurrentIndex() 和 PathView.decrementCurrentIndex() 仅将 PathView 移动到下一个元素.例如，您在索引 1 上，快速调用 PathView.incrementCurrentIndex() 4 次，结果是您移动到索引 2 而不是 5。我制作了一个 Animation移动 PathView(但不确定它是否朝正确的方向移动)。另请注意 onDragStarted: { scrollViewAnimation.stop() }。
2. 为了在滚动时去除空白，我刚刚将 PathPercent { value: 0.48 } 和 PathPercent { value: 0.52 } 修改为 PathPercent { value: 0.45 } 和 PathPercent { value: 0.55 }