A collapsible nested list example in QML

nested_list.qml

import QtQuick 1.1

Item {
    width: 200
    height: 300

    ListView {
        anchors.fill: parent
        model: nestedModel
        delegate: categoryDelegate
    }

    ListModel {
        id: nestedModel
        ListElement {
            categoryName: "Veggies"
            collapsed: true

            // A ListElement can't contain child elements, but it can contain
            // a list of elements. A list of ListElements can be used as a model
            // just like any other model type.
            subItems: [
                ListElement { itemName: "Tomato" },
                ListElement { itemName: "Cucumber" },
                ListElement { itemName: "Onion" },
                ListElement { itemName: "Brains" }
            ]
        }

        ListElement {
            categoryName: "Fruits"
            collapsed: true
            subItems: [
                ListElement { itemName: "Orange" },
                ListElement { itemName: "Apple" },
                ListElement { itemName: "Pear" },
                ListElement { itemName: "Lemon" }
            ]
        }

        ListElement {
            categoryName: "Cars"
            collapsed: true
            subItems: [
                ListElement { itemName: "Nissan" },
                ListElement { itemName: "Toyota" },
                ListElement { itemName: "Chevy" },
                ListElement { itemName: "Audi" }
            ]
        }
    }

    Component {
        id: categoryDelegate
        Column {
            width: 200

            Rectangle {
                id: categoryItem
                border.color: "black"
                border.width: 5
                color: "white"
                height: 50
                width: 200

                Text {
                    anchors.verticalCenter: parent.verticalCenter
                    x: 15
                    font.pixelSize: 24
                    text: categoryName
                }

                Rectangle {
                    color: "red"
                    width: 30
                    height: 30
                    anchors.right: parent.right
                    anchors.rightMargin: 15
                    anchors.verticalCenter: parent.verticalCenter

                    MouseArea {
                        anchors.fill: parent

                        // Toggle the 'collapsed' property
                        onClicked: nestedModel.setProperty(index, "collapsed", !collapsed)
                    }
                }
            }

            Loader {
                id: subItemLoader

                // This is a workaround for a bug/feature in the Loader element. If sourceComponent is set to null
                // the Loader element retains the same height it had when sourceComponent was set. Setting visible
                // to false makes the parent Column treat it as if it's height was 0.
                visible: !collapsed
                property variant subItemModel : subItems
                sourceComponent: collapsed ? null : subItemColumnDelegate
                onStatusChanged: if (status == Loader.Ready) item.model = subItemModel
            }
        }

    }

    Component {
        id: subItemColumnDelegate
        Column {
            property alias model : subItemRepeater.model
            width: 200
            Repeater {
                id: subItemRepeater
                delegate: Rectangle {
                    color: "#cccccc"
                    height: 40
                    width: 200
                    border.color: "black"
                    border.width: 2

                    Text {
                        anchors.verticalCenter: parent.verticalCenter
                        x: 30
                        font.pixelSize: 18
                        text: itemName
                    }
                }
            }
        }
    }
}