ImageModel.hpp Example File

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    #ifndef IMAGEMODEL_HPP
    #define IMAGEMODEL_HPP

    #include <bb/cascades/DataModel>
    #include <bb/cascades/Image>

    #include <QContiguousCache>

    /**
     * The ImageModel is a custom DataModel that provides a list of 10000 images.
     * However the model does not keep all the images in memory all the time but only
     * the subset that is currently needed by the view.
     * For the implementation it utilizes the QContiguousCache class.
     */
    class ImageModel : public bb::cascades::DataModel
    {
        Q_OBJECT

        /**
         * A property that provides the number of currently cached items. We use it
         * to show that number in the UI.
         */
        Q_PROPERTY(int cachedItemCount READ cachedItemCount NOTIFY cachedItemCountChanged)

    public:
        ImageModel(QObject *parent = 0);

        // These methods are re-implemented from the DataModel base class
        int childCount(const QVariantList &indexPath);
        bool hasChildren(const QVariantList &indexPath);
        QString itemType(const QVariantList &indexPath);
        QVariant data(const QVariantList &indexPath);

        // The accessor method for the cached item count property
        int cachedItemCount() const;

    Q_SIGNALS:
        // The change notification signal for the cached item count property
        void cachedItemCountChanged();

    private:
        // An internal helper method to refill the cache in a given range
        void cacheRows(int from, int to) const;

        // An internal helper method to create a new Image element for the given position
        bb::cascades::Image fetchRow(int position) const;

        // The contiguous cache that caches all the Image objects
        mutable QContiguousCache<bb::cascades::Image> m_rows;

        // The number of images this model provides (10000 by default)
        const int m_count;
    };

    #endif