QML: Dynamic view re-ordering in original model

问题

Implemented QML Dynamic View Ordering by Dragging View Items using this Qt tutorial: QML Dynamic View Ordering Tutorial. Original underlying model is QAbstractListModel descendant in our case. Model stores data in a QList<QObject*> objectList; field type. Works fine, however item ordering changed in proxy DelegateModel only.

How to change items order automatically in original underlying model as well for other C++ and QML consumers where order matters? Or I could we otherway access some resulted (sorted) List Model model from C++ somehow?

Thanks for any help!

回答1:

In the QML Dynamic View Ordering Tutorial 3 example I've replaced visualModel.items.move() call with my ObjectListModel::move() method like this:

ObjectListModel : public QAbstractListModel:

void ObjectListModel::move(int from, int to)
{
    if(0 <= from && from < count() && 0 <= to && to < count() && from != to) {
        if(from == to - 1) // Allow item moving to the bottom
            to = from++;

        beginMoveRows(QModelIndex(), from, from, QModelIndex(), to);
        objectList.move(from, to);
        endMoveRows();
    }
}

Delegate component:

DropArea {
    anchors { fill: parent; }

    onEntered: {
        let from = drag.source.DelegateModel.itemsIndex
        let to = mouseArea.DelegateModel.itemsIndex
        objectListModel.move(from, to)
    }
}

And above works perfectly for the ListView and ObjectListModel itself - I have checked: items (and therefore objects) are moved correctly, indexes are correct, C++ consumers works just fine and take new order into account correctly, etc.

However another consumer like MapItemView fails to use the model after beginMoveRows/endMoveRows calls: moved item disappeared on the map and other manipulations with an item crashes the app.

 Map {
     ...
     MapItemView {
         model: objectListModel

         delegate: SomeItemIndicator {
         }
     }
 }

Probably QTBUG-81076 bug. Some other hacks like emitting dataChanged() signal, etc do not help as well. Any ideas how to solve this situation?

来源：https://stackoverflow.com/questions/59537237/qml-dynamic-view-re-ordering-in-original-model

标签

listview

drag-and-drop

qml

qt5