QML TreeView 在向模型添加新数据后未在运行时更新

Question

我有一个通过 QStandardItemModel 获取数据的 QML TreeView。当应用程序为运行时，我按下了一个添加新条目的按钮。我知道数据在变化，但 QML TreeView 没有更新。我也试过 beginResetModel() 和 endResetModel()。加载应用程序时，数据在 TreeView 中正确显示，但在修改模型中的数据时，TreeView 不会更改。

treeviewmodel.cpp

#include <QDebug>
#include <QStandardItemModel>
#include "treeviewmodel.h"

TreeViewModel::TreeViewModel(QObject *parent) :
    QStandardItemModel(parent)
{
    m_roleNameMapping[TreeViewModel_Role_Name] = "name_role";

    QStandardItem* entry;
    entry = new QStandardItem(QString("my_entry"));
    entry->setData("abc", TreeViewModel_Role_Name);

    auto childEntry = new QStandardItem( "my_child_entry" );
    childEntry->setData( "def",TreeViewModel_Role_Name);
    entry->appendRow(childEntry);
    appendRow( entry );

}
TreeViewModel& TreeViewModel::Instance()
{
    static TreeViewModel instance; //Guaranteed to be destroyed
    return instance;
}
void TreeViewModel::addEntry()
{
    qDebug () << "Adding entry...";

    QStandardItem* entry;
    entry = new QStandardItem(QString("my_entry"));
    entry->setData("Second Entry", TreeViewModel_Role_Name);
    auto childEntry = new QStandardItem( "my_child_entry" );
    childEntry->setData( "Second Entry Child",TreeViewModel_Role_Name);
    entry->appendRow(childEntry);
    appendRow( entry );
    qDebug () << rowCount(); //Increases everytime I call the function
                             //Data is being added
}
QHash<int, QByteArray> TreeViewModel::roleNames() const
{
    return m_roleNameMapping;
}

main.qml

import treeModel 1.0
...
MyTreeModel {
    id: theModel
}

//Left Tree View
Rectangle {
    id: leftView
    Layout.minimumWidth: 50
    width: 200
    //Layout.fillWidth: true
    color: "white"
    TreeView {
        id: treeView
        anchors.fill: parent
        model: theModel
        TableViewColumn {
            role: "name_role"
            title: "Name"
        }
        TableViewColumn {
            role: "description_role"
            title: "Description"
        }
    }
}

ToolButton {
    iconSource: "lock.png"
    onClicked: {
    treeviewmodel.addEntry()
    }
}

main.cpp

QQmlContext* treeViewModelCtx = engine.rootContext();
treeViewModelCtx->setContextProperty("treeviewmodel", &TreeViewModel::Instance());

//Register types
qmlRegisterType<TreeViewModel>("treeModel", 1, 0, "MyTreeModel" );

Answer 1

希望这个例子对您有所帮助。不幸的是，我没有你的完整代码来查看问题出在哪里。

也许关键是 data 和 roleNames 方法。

在这个例子中，我们还有一个名为 addButton 的按钮来添加新项目。

main.cpp

#include "animalmodel.h"

#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <qqmlcontext.h>
#include <qqml.h>

int main(int argc, char ** argv)
{
    QGuiApplication app(argc, argv);

    AnimalModel model;
    model.addAnimal("Wolf", "Medium");
    model.addAnimal("Polar bear", "Large");
    model.addAnimal("Quoll", "Small");

    QQmlApplicationEngine engine;

    QQmlContext *ctxt = engine.rootContext();
    ctxt->setContextProperty("myModel", &model);

    engine.load(QUrl(QStringLiteral("qrc:/view.qml")));

    return app.exec();
}

animalmodel.h

#ifndef ANIMALMODEL_H
#define ANIMALMODEL_H

#include <QStandardItemModel>

class AnimalModel : public QStandardItemModel
{
    Q_OBJECT
public:
    enum AnimalRoles {
        TypeRole = Qt::UserRole + 1,
        SizeRole
    };

    AnimalModel(QObject *parent = 0);

    Q_INVOKABLE void addAnimal(const QString &type, const QString &size);

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;

protected:
    QHash<int, QByteArray> roleNames() const;
};

#endif // ANIMALMODEL_H

animalmodel.cpp

#include "animalmodel.h"

AnimalModel::AnimalModel(QObject *parent)
    : QStandardItemModel(parent)
{

}

void AnimalModel::addAnimal(const QString &type, const QString &size)
{
    QStandardItem* entry = new QStandardItem();
    entry->setData(type, TypeRole);

    auto childEntry = new QStandardItem();
    childEntry->setData(size, SizeRole);
    entry->appendRow(childEntry);

    appendRow( entry );
}

QVariant AnimalModel::data(const QModelIndex & index, int role) const {
    QStandardItem *myitem = itemFromIndex(index);

    if (role == TypeRole)
        return myitem->data(TypeRole);
    else if (role == SizeRole) {
        if (myitem->child(0) != 0)
        {
            return myitem->child(0)->data(SizeRole);
        }
    }

    return QVariant();
}

QHash<int, QByteArray> AnimalModel::roleNames() const {
    QHash<int, QByteArray> roles;
    roles[TypeRole] = "type";
    roles[SizeRole] = "size";
    return roles;
}

QML TreeView 在向模型添加新数据后未在运行时更新

QML TreeView not updating at runtime after adding new data to the model

c++

qt

qml

qtquick2

qtquickcontrols