QML：原始模型中的动态视图重新排序 [英] QML: Dynamic view re-ordering in original model

问题描述

使用此Qt教程通过拖动视图项来实现QML动态视图排序： QML动态视图订购教程。在我们的案例中，原始基础模型是 QAbstractListModel 子孙。模型将数据存储在 QList< QObject *>中。 objectList; 字段类型。工作正常，但是仅在代理 DelegateModel 中更改了项目顺序。

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.

如何在原始基础模型中以及在其他重要的C ++和QML使用者中自动更改项目订单？还是我可以以某种方式通过C ++访问某些结果（排序的）列表模型模型？

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?

谢谢您的帮助！

推荐答案

在 QML动态视图订购教程3 示例 visualModel.items.move（）用我的 ObjectListModel :: move（）方法调用：

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();
    }
}

代理组件：

DropArea {
    anchors { fill: parent; }

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

以上功能对于 ListView 和 ObjectListModel 本身-我检查过：项目（因此对象）正确移动，索引正确，C ++使用者工作正常且正确考虑新订单，等等。

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.

但是另一个消费者，例如 MapItemView beginMoveRows / endMoveRows 调用后，$ c>无法使用该模型：移动的项目在地图上消失，并且其他操作一项使应用程序崩溃。

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 {
         }
     }
 }

已报告 QTBUG-81076 错误，已确认。

Reported QTBUG-81076 bug, which is confirmed.

解决方法：

现在找到解决方法：创建了第二个重复模型，其内容在第一个模型的每次更改，每次添加/删除/移动（重新排序）时，将完全替换。由于 beginResetModel / endResetModel 对于 MapItemView 正常工作，上述方法有效。因此， MapItemView 现在仅使用第二个模型。因此，在每次第一个模型更改时，都会为第二个模型调用此方法：

Found workaround for now: created 2nd duplicate model which content will be replaced completely on every change in the 1st model on every add/delete/moving(reordering). Above works since beginResetModel/endResetModel works correctly for MapItemView. So MapItemView now utilizes only the 2nd model. So on every 1st model change this method is called for the 2nd model:

QObjectList ObjectListModel::swapObjectList(const QObjectList& newlist)
{
    QObjectList oldlist(_objectList);
    beginResetModel();
    _objectList = newlist;
    endResetModel();
    return oldlist;
}

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