QML中含DelegateModelGroups的DelegateModel拖拽功能异常求助

参考《Moving item in QML GridView》的拖拽实现代码，在GridView中拖拽图标时出现以下错误：

• file:///home/christoforos/Videos/launchpadPlasmaMod/contents/ui/AllApps.qml:151:11: QML MyDelegateModel (parent or ancestor of DelegateModelGroup): move: from index out of range
• file:///home/christoforos/Videos/launchpadPlasmaMod/contents/ui/AllApps.qml:260: TypeError: Cannot read property 'visualIndex' of null

我的GridView使用的是包含DelegateModelGroups的DelegateModel，相关代码如下：

MyDelegateModel.qml #

import QtQuick 2.15
import QtQuick.Controls 2.15
import QtQml.Models 2.4
DelegateModel {
    property int from: 0
    property int to: 10
    groups: [
        DelegateModelGroup {
            id: newItems
            name: "new"
            includeByDefault: true
            onCountChanged: {
                newItems.setGroups(from, to - from, ["new","visible"]);
            }
        },
        DelegateModelGroup {
            id: visibleItems
            name: "visible"

        }

    ]
    filterOnGroup: "visible"
}

GridView代码 #

GridView {
    id: mainGrid
    cellWidth: 195
    cellHeight: 155
    anchors.fill: parent
    property int lastChangedIndex: -1
    property int xAxis: 0
    property int yAxis: 0
    displaced: Transition {
            NumberAnimation {
                properties: "x,y"
                easing.type: Easing.OutQuad
            }
        }
    model:MyDelegateModel{
        id:visualModel
        from:index*35
        to:Math.min(from + 35, appsModel.count)
        model:appsModel
        delegate: MouseArea{
            id: delegateRoot
            property bool held: false
            property int visualIndex:index
            width: mainGrid.cellWidth-45; height: mainGrid.cellHeight-45;
            drag.target: held ? box : undefined
            onClicked:{
                executable.exec("$(gtk-launch " + appsModel.get(index).display + ")") ;
                console.log(appsModel.get(index).display)
            }
            pressAndHoldInterval : 200
            onPressAndHold: {
                    held = true
                    box.opacity = 0.5
                    box.z = 10
                }
            onReleased: {
                    if (held === true) {
                        held = false
                        box.opacity = 1
                        box.Drag.drop()
                        box.z = 1
                    } else {
                        //action on release
                    }
                }
            Kirigami.Icon {
                id: box
                parent: mainGrid
                x: delegateRoot.x; y: delegateRoot.y-10;
                width: delegateRoot.width;
                height:delegateRoot.height;
                source: appicon
                Text {
                    anchors.top: parent.bottom
                    anchors.horizontalCenter:parent.horizontalCenter
                    text: name
                    font.pixelSize: 12
                    color:"black"
                }
                    Drag.active: delegateRoot.drag.active
                    Drag.source: delegateRoot
                    Drag.hotSpot.x: 36
                    Drag.hotSpot.y: 36
                SequentialAnimation on rotation {
                     NumberAnimation { to:  4; duration: 60 }
                     NumberAnimation { to: -4; duration: 120 }
                     NumberAnimation { to:  0; duration: 60 }
                        running: delegateRoot.held
                        loops: Animation.Infinite; alwaysRunToEnd: true
                }
                    states: [
                        State {
                            when: box.Drag.active
                            ParentChange {
                                target: box
                                parent: mainGrid
                            }
                            AnchorChanges {
                                target: box
                                anchors.horizontalCenter: undefined
                                anchors.verticalCenter: undefined
                            }
                        }
                    ]
                }
                DropArea {
                    id: dropArea
                    anchors {
                        fill: parent
                        margins: 15
                    }
                    signal trigger
                    Timer {
                        id: dropZoneTimer
                        interval: 1000
                        onTriggered: {
                            dropArea.trigger()
                        }
                    }
                    onTrigger: {
                        visualModel.items.move(drag.source.visualIndex,
                                               delegateRoot.visualIndex)
                        mainGrid.lastChangedIndex = delegateRoot.visualIndex
                    }
                    onEntered: {
                        if (drag.source.visualIndex !== delegateRoot.visualIndex) {
                            dropZoneTimer.start()
                        }
                    }
                    onExited: {
                        dropZoneTimer.stop()
                        mainGrid.lastChangedIndex = -1
                    }
                    onDropped: {
                        if (mainGrid.lastChangedIndex !== delegateRoot.visualIndex) {
                            visualModel.items.move(drag.source.visualIndex, delegateRoot.visualIndex)
                        }
                        console.log("drag from",drag.source.visualIndex,"drop to",delegateRoot.visualIndex )
                    }
                }
              }
           }
        }

已调试一整天仍未解决问题，恳请各位提供帮助。

内容的提问来源于stack exchange，提问作者cgiannakidis