QML PathView 中的 SetRootIndex

2022-01-19 00:00:00 qt qml c++

我正在使用 QML PathView 来展示我的模型.这样的模型继承自 QStandardItemModel 并具有两级数据(父项和子项).我需要在 PathView 中显示模型的第二级，即选定父级的所有子级.使用 QAbstractItemView 可以通过使用setRootIndex 函数.如何使用 PathView 获得相同的结果?

I'm using a QML PathView to show my model. Such a model inherits from QStandardItemModel and has two levels of data (parent items and child items). I need to show the second level of the model in the PathView, i.e. all the children of a selected parent. Using a QAbstractItemView this result can be achieve by using the setRootIndex function. How can I achieve the same result with a PathView?

有人可以帮助我吗?提前致谢.

Can someone help me? Thanks in advance.

这里是一个模型示例:

newPetModel::newPetModel()
{
...
 fillModel();
}
...
void newPetModel::fillModel()
{
 QStandardItem* rootItem = invisibleRootItem();
 // groups
 QStandardItem* GroupAnimals = new QStandardItem();
 rootItem->setChild(rootItem->rowCount(), GroupAnimals);
 GroupAnimals->setData(QString("Animals"),nameRole);

 QStandardItem* GroupPlants = new QStandardItem();
 rootItem->setChild(rootItem->rowCount(), GroupPlants);
 GroupPlants->setData(QString("Plants"),nameRole);

 QStandardItem* GroupInsects = new QStandardItem();
 rootItem->setChild(rootItem->rowCount(), GroupInsects);
 GroupInsects->setData(QString("Insects"),nameRole);
 // items
 QStandardItem* Cat = new QStandardItem();
 GroupAnimals->setChild(GroupAnimals->rowCount(), Cat);
 Cat->setData(QString("Cat"),nameRole);
 Cat->setData(QString("qrc:/cat.jpg"),imgRole);

 QStandardItem* Dog = new QStandardItem();
 GroupAnimals->setChild(GroupAnimals->rowCount(), Dog);
 Dog->setData(QString("Dog"),nameRole);
 Dog->setData("qrc:/dog.jpg",imgRole);`enter code here`
 //-----
 QStandardItem* Peas = new QStandardItem();
 GroupPlants->setChild(GroupPlants->rowCount(), Peas);
 Peas->setData(QString("Peas"),nameRole);
 Peas->setData("qrc:/peas.jpg",imgRole);
 //-----
 QStandardItem* Spider = new QStandardItem();
 GroupInsects->setChild(GroupInsects->rowCount(), Spider);
 Spider->setData(QString("Spider"),nameRole);
 Spider->setData("qrc:/peas.jpg",imgRole);

 QStandardItem* Fly = new QStandardItem();
 GroupInsects->setChild(GroupInsects->rowCount(), Fly);
 Fly->setData(QString("Fly"),nameRole);
 Fly->setData("qrc:/fly.jpg",imgRole);
}

推荐答案

QML 适用于列表模型，正如您在您的案例中看到的那样.然而，这个限制可以通过使用 DelegateModel.引用文档:

QML works with list models, as you have seen also in your case. However, this limitation can be easily overcome by using DelegateModel. Quoting the documentation:

通常不需要创建 DelegateModel.但是，当 QAbstractItemModel 子类用作模型时，它对于操作和访问 modelIndex 很有用.此外，DelegateModel 与 Package 一起用于为多个视图提供代理，并与 DelegateModelGroup 一起用于对代理项进行排序和过滤.

It is usually not necessary to create a DelegateModel. However, it can be useful for manipulating and accessing the modelIndex when a QAbstractItemModel subclass is used as the model. Also, DelegateModel is used together with Package to provide delegates to multiple views, and with DelegateModelGroup to sort and filter delegate items.

这种 QML 类型有一个属性 根索引.再次引用文档:

Such QML type has a property rootIndex. Quoting again the documentation:

QAbstractItemModel 提供了一个层次结构的数据树，而 QML 只对列表数据进行操作.rootIndex 允许此模型提供 QAbstractItemModel 中任何节点的子节点.

QAbstractItemModel provides a hierarchical tree of data, whereas QML only operates on list data. rootIndex allows the children of any node in a QAbstractItemModel to be provided by this model.

这是您需要设置(和重置)的属性，如链接文档的示例中所述.请注意，通过使用 DelegateModel 不应定义 PathView 中的委托.一个工作示例(visualdatamodel/slideshow.qml)可在以下路径下的标准框架分发中找到:

This is the property you need to set (and reset), as described in the example of the linked documentation. Note that by using DelegateModel the delegate in your PathView should not be defined. A working example (visualdatamodel/slideshow.qml) is available in the standard framework distribution under the path:

Qt/QtXXX/Examples/Qt-5.4/quick/views

最后注意 DelegateModel 和 VisualDataModel 经常以可互换的方式使用，因为

Finally note that DelegateModel and VisualDataModel are often used in an interchangeable way since

由于兼容性原因，此类型(VisualDataModel)由 Qt QML 模块提供.相同的实现现在主要用作 Qt QML 模型中的 DelegateModel 模块.

This type (VisualDataModel) is provided by the Qt QML module due to compatibility reasons. The same implementation is now primarily available as DelegateModel in the Qt QML Models module.

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