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QML ListView in qml is not updated when model changed



  • I am trying to update a model in a QML ListView from a cpp file..

    this is my model implementation albummodel.h

    
    
    #include <QAbstractListModel>
    #include <QStringList>
    #include <QQmlListProperty>
    
    class Album
    {
    public:
        Album(const QString &type, const QString &size);
    
    
        QString type() const;
        QString size() const;
    
    private:
        QString m_type;
        QString m_size;
    
    };
    
    class AlbumModel : public QAbstractListModel
    {
        Q_OBJECT
        Q_PROPERTY(QQmlListProperty<QObject> myModel NOTIFY listChanged)
    
    public:
    
        enum AlbumRoles {
            TypeRole = Qt::UserRole + 1,
            SizeRole
        };
    
        AlbumModel(QObject *parent = 0);
    
        //QQmlListProperty<QObject> getList();
    
        void addAlbum(const Album &album);
    
        int rowCount(const QModelIndex & parent = QModelIndex()) const;
    
        QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
    
    protected:
        QHash<int, QByteArray> roleNames() const;
    private:
        QList<Album> m_albums;
    signals:
        void listChanged();
    #include <QAbstractListModel>
    #include <QStringList>
    #include <QQmlListProperty>
    
    class Album
    {
    public:
        Album(const QString &type, const QString &size);
    
    
        QString type() const;
        QString size() const;
    
    private:
        QString m_type;
        QString m_size;
    
    };
    
    class AlbumModel : public QAbstractListModel
    {
        Q_OBJECT
        Q_PROPERTY(QQmlListProperty<QObject> myModel NOTIFY listChanged)
    
    public:
    
        enum AlbumRoles {
            TypeRole = Qt::UserRole + 1,
            SizeRole
        };
    
        AlbumModel(QObject *parent = 0);
    
        //QQmlListProperty<QObject> getList();
    
        void addAlbum(const Album &album);
    
        int rowCount(const QModelIndex & parent = QModelIndex()) const;
    
        QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
    
    protected:
        QHash<int, QByteArray> roleNames() const;
    private:
        QList<Album> m_albums;
    signals:
        void listChanged();
    };
    

    This is my albummodel.cpp

    #include "albummodel_mediaplayer.h"
    
    Album::Album(const QString &type, const QString &size)
        : m_type(type), m_size(size)
    {
    }
    
    QString Album::type() const
    {
        return m_type;
    }
    
    QString Album::size() const
    {
        return m_size;
    }
    
    AlbumModel::AlbumModel(QObject *parent)
        : QAbstractListModel(parent)
    {
    }
    
    void AlbumModel::addAlbum(const Album &album)
    {
        beginInsertRows(QModelIndex(), rowCount(), rowCount());
        m_albums << album;
        endInsertRows();
    
        emit listChanged();
    }
    
    int AlbumModel::rowCount(const QModelIndex & parent) const {
        Q_UNUSED(parent);
        return m_albums.count();
    }
    
    QVariant AlbumModel::data(const QModelIndex & index, int role) const {
        if (index.row() < 0 || index.row() >= m_albums.count())
            return QVariant();
    
        const Album &Album = m_albums[index.row()];
        if (role == TypeRole)
            return Album.type();
        else if (role == SizeRole)
            return Album.size();
        return QVariant();
    }
    
    
    QHash<int, QByteArray> AlbumModel::roleNames() const {
        QHash<int, QByteArray> roles;
        roles[TypeRole] = "type";
        roles[SizeRole] = "size";
        return roles;
    }
    
    
    /*QQmlListProperty<QObject> AlbumModel::getList(){
        return QQmlListProperty<QObject>(this, *list);
    }*/
    

    and my qml file

    ListView {
    model: myModel
    
    ....
    }
    

    But the model isn't updated.....Can someone help me to get the connection right?


  • Moderators

    @lomilomi said in QML ListView in qml is not updated when model changed:

    Q_PROPERTY(QQmlListProperty<QObject> myModel NOTIFY listChanged)

    This is wrong, you don't need any Q_PROPERTY when using a QAbstract*Model.

    In QML, you should simply point model to an instance of AlbumModel. I don't know how you create/ pass it from C++ to QML so I can't exactly tell you how to do it in your case.

    In general, though, setting it through root context property of the QQmlEngine is the easiest route and works well.



  • @sierdzio

    This is my main program

    void main() {
          qmlRegisterType<AlbumModel>("AlbumModel",1,0,"AlbumModel");
          Album g("test", "test");
           AlbumModel h();
           h.addAlbum(g);
      }
    

    Qml file

    import AlbumModel 1.0 ListView { model: AlbumModel.myModel delegate: playListThumbnail Component { id: playListThumbnail
    
                Item {
     Text {
                        id: albumTitleText
                        text:  type//item_title 
    }}
    ....
    }
    

  • Moderators

    You create 2 different instances of AlbumModel: one in C++ and one in QML. Then you add an album in C++ - but obviously the other object in QML won't know about it.

    Solution: do not create 2 objects. For example, in C++:

    void main() {
          Album g("test", "test");
           AlbumModel h();
           h.addAlbum(g);
           engine.rootContext()->setContextProperty("AlbumModel", &h);
      }
    

    With this it should work fine.



  • This is almost verbatim the same as this example on the wiki


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