Add and Delete items in Swipe view on Current index change.

[Anup deshpande]

Hi,
I am trying to add and delete elements in Swipe view when ever my current index is changed. initially i load the swipe view with 15 items.
When ever i swipe to left, am trying to remove an item at the beginning and trying to add an item at the end so that my number of items in my swipe view is maintained with 15 elements.
I would like to do vise versa(right swiping).
Im not able to achieve it. Can somebody help.
Note
I have to load 10k elements. I Dont want to use loader or Repeater.

import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 2.2
import QtQuick.Window 2.3

Window {
    visible: true
    width: 500
    height: 400
    title: qsTr("Hello World")
    property int _count:_swipeView.count
    property int  prevIndex: -1
    property Component comp



    SwipeView{
        id:_swipeView
        width: parent.width
        height: parent.height
        currentIndex: 0

        onCurrentIndexChanged: {
            console.log("Changing current index and previous "+currentIndex,prevIndex)
            if (prevIndex==-1){
                console.log("First time access ="+prevIndex + " Current Index="+currentIndex)
                prevIndex= currentIndex;
                return
            }
            if (prevIndex<currentIndex){
                console.log("Moving left PrevIndex="+prevIndex + " Current Index="+currentIndex)
                removeElementAtBeginning()
                addElementAtEnd()
                prevIndex=currentIndex
                return
            }
            if (prevIndex>currentIndex){
                console.log("Moving Right PrevIndex="+prevIndex + " Current Index="+currentIndex)
                addElementAtBeginning()
                removeElementAtEnd()
                prevIndex=currentIndex
                return
            }

        }
    }

    function createSwipeViewObjects(){
        for(var i=0;i<15;++i){
            comp= Qt.createComponent("SwipeSource.qml")
            var obj=comp.createObject(_swipeView);
            obj.text="Anup "+i
            _swipeView.insertItem(i,obj)
        }
    }

    function addElementAtEnd(){
        ++_count
        comp= Qt.createComponent("SwipeSource.qml")
        var obj=comp.createObject(_swipeView);
        obj.text= "Anup "+_count

        _swipeView.addItem(obj)
        console.log("current index after adding at end"+_swipeView.currentIndex)

    }

    function removeElementAtBeginning(){
        _swipeView.takeItem(0)
        console.log("current index after removing at beginning"+_swipeView.currentIndex)

    }

    function addElementAtBeginning(){

        comp= Qt.createComponent("SwipeSource.qml")
        var obj=comp.createObject(_swipeView);
        obj.text="dummy"
        _swipeView.insertItem(0,obj)
        console.log("adding Element At Beginning "+_swipeView.currentIndex)


    }

    function removeElementAtEnd(){
        //  console.log("Dummy Implementation")


    }


    Component.onCompleted: {
        createSwipeViewObjects()

    }
}


swipeSource.qml
import QtQuick 2.0

Rectangle{
    width : 300
    height : 400
    color: Qt.rgba(0,0,1,0.5)
    property alias text: t1.text
    Text {
        id:t1
        anchors.centerIn: parent
        font.pixelSize: 30;
        color: "blue"

    }

    Component.onDestruction: {
        console.log("Destroying..")
    }
}

[J.Hilk]

Swipe view, probably not what you want, but path view should work,

take this example:

import QtQuick 2.12
import QtQuick.Controls 2.12
import QtQuick.Window 2.2
import QtQuick.Layouts 1.12

Window
{
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    color: "green"
    id: win

    Rectangle {
        id:root
        anchors.fill: parent


        function createModel () {
            var model= []
            for(var i=0; i < 255; i++){
                model.push(Qt.rgba(i/255,i/255,i/255, 255));
            }
            return model;
        }

        property var myModel: createModel()
        property int loopIndex: 0

        ListModel {
                id: model
                ListElement {}
                ListElement {}
                ListElement {}
            }

            Component {
                id: delegate
                Rectangle {
                    id: wrapper
                    width: view.width
                    height: view.height
                    color: root.myModel[root.loopIndex ]

                    Text {
                        anchors.centerIn: parent
                        font.pointSize: 26
                        font.bold: true
                        color: "white"
                        text:root.loopIndex
                    }
                }
            }

            Timer {
                running:  true
                repeat: true
                interval: 500
                onTriggered: view.incrementCurrentIndex()
            }

            PathView {
                id: view
                anchors.fill: parent
                snapMode: PathView.SnapOneItem
                highlightRangeMode: PathView.StrictlyEnforceRange
                currentIndex: 0
                property int lastIndex: 0
                onCurrentIndexChanged: {
                    var dif = currentIndex - lastIndex
                    if(dif == 1 || dif == -2)
                        root.loopIndex ++
                    if(dif == -1 || dif == 2)
                        root.loopIndex--
                    lastIndex = currentIndex
                }
                model: model
                delegate: delegate
                path: Path {
                    startX: -view.width / 2  // let the first item in left
                    startY: view.height / 2  // item's vertical center is the same as line's

                    PathLine {
                        relativeX: view.width * view.model.count  // all items in lines
                        relativeY: 0
                    }
                }
            }
    }
}

[Anup deshpande]

@J-Hilk Thank you. it works !!:) but there is a bug.
The item at the 0th and last index keeps rotating, i.e swipe has to stop once we reach end or come to starting index. is there a way to stop it.?

[J.Hilk]

@Anup-deshpande just a matter of catching the edge cases I believe.

My above example can be adjusted with the following change to the onCurrentIndexChanged behavior :

onCurrentIndexChanged: {
                    var dif = currentIndex - lastIndex
                    if(dif == 1 || dif == -2){
                        if(root.loopIndex == root.myModel.length -1)
                            root.loopIndex = 0
                        else
                            root.loopIndex ++
                    }
                    if(dif == -1 || dif == 2){
                        if(root.loopIndex == 0)
                            root.loopIndex = root.myModel.length -1
                        else
                            root.loopIndex--
                    }
                    lastIndex = currentIndex
                }