How to access ListView's current item from qml

问题

I have an application that stores and edits notes. The list of notes is displayed in a listview like this:

Page {
        id: noteList
        title: i18n.tr("QNote")
        visible: false

        Column {
            anchors.fill: parent

            ListView {
                anchors.fill: parent
                model: notes
                delegate: ListItem.Standard {
                    text: Title
                    onClicked: editNote(NoteText, Title, modelData);
                    progression: true
                }
            }
        }
    }

function editNote(text, title, item) {
    pageStack.push(noteEdit, {title: title, text: text});
    handler.setActiveItem(item);
}

The notes item is a NoteListModel that subclasses the QAbstractListModel and contains NoteListItems. What I would like to do is to store the currently selected NoteListItem so I could easily access the Note object inside when the user wants to save the modified note. However, I don't know how to access the backing NoteListItem from the qml delegate. the modelData seems to be something else. Is there any way to do so? If i could wrap the Note object in a QVariant I could access it easily through roles but when I tried it like this

QVariant NoteListItem::data(int role) {
    switch (role) {
    case Title:
        return note.getTitle();
    case NoteText:
        return note.getText();
    case NoteObject:
        return QVariant::fromValue(note);
    default:
        return QVariant();
    }
}

it resulted in a compiler error saying

qmetatype.h:642: error: invalid application of 'sizeof' to incomplete type 'QStaticAssertFailure'

Or should i try to access the selected list item from the backing code? Is there any way for that? Dou you have any ideas?

Thanks for your time. Regards, Peter

回答1:

This took me a very long time to find, as there are many incorrect solutions on Stackoverflow.

The pure QML way is to use a DelegateModel and access it from QML as follows:

import QtQuick 2.4
import QtQml.Models 2.1

ListView {
    property var currentSelectedItem

    onCurrentItemChanged{
            // Update the currently-selected item
            currentSelectedItem = myDelegateModel.items.get(currentIndex).model;
            // Log the Display Role
            console.log(currentSelectedItem.display);
    }

    model: DelegateModel {
        id: myDelegateModel
        model: myAbstractItemModel
        delegate: {
            // Define delegates here
        }
    }
}

This line returns an object (var) that you can access in the same way as within a delegate: myDelegateModel.items.get(currentIndex).model

This example assumes you are only using the default DelegateModelGroup.

See http://doc.qt.io/qt-5/qml-qtqml-models-delegatemodel.html and http://doc.qt.io/qt-5/qml-qtqml-models-delegatemodelgroup.html#get-method method

来源：https://stackoverflow.com/questions/16389831/how-to-access-listviews-current-item-from-qml