Question

基于Qt给出的QML example treeview，如何在不破坏模型的情况下清除整个树模型？本质上，我想擦除树上的所有项目/元素，而又不破坏树本身。我正在使用的特定代码是donated by eyllanesc。

我修改了原始代码，将*elementFromIndex(...)设为Q_INVOKABLE

在QML中，我尝试过：

elementFromIndex(treemodel.index(0,0))->clear();
elementFromIndex(-1)->clear();

，然后意识到QML不理解指针。因此，由于树的逻辑，我有点茫然。我知道我本质上需要调用类似的东西： myRootItem.clear() 但我不知道如何引用myRootItem的身份。 TreeModel本身内部没有clear（）函数，只有TreeElement对象。

Complete code example here

TreeElement.h

class TreeElement : public QObject
{
    Q_OBJECT
public:
    Q_PROPERTY(QQmlListProperty<TreeElement> items READ items)
    Q_CLASSINFO("DefaultProperty", "items")
    TreeElement(QObject *parent = Q_NULLPTR);

    Q_INVOKABLE TreeElement *parentItem() const;
    bool insertItem(TreeElement *item, int pos = -1);
    QQmlListProperty<TreeElement> items();

    TreeElement *child(int index) const;
    void clear();

    Q_INVOKABLE int pos() const;
    Q_INVOKABLE int count() const;

private:
    static void appendElement(QQmlListProperty<TreeElement> *property, TreeElement *value);
    static int countElement(QQmlListProperty<TreeElement> *property);
    static void clearElement(QQmlListProperty<TreeElement> *property);
    static TreeElement *atElement(QQmlListProperty<TreeElement> *property, int index);

    QList<TreeElement *> m_childs;
    TreeElement *m_parent;
};

TreeModel.h

class TreeModel : public QAbstractItemModel
{
    Q_OBJECT
public:
    Q_PROPERTY(QQmlListProperty<TreeElement> items READ items)
    Q_PROPERTY(QVariantList roles READ roles WRITE setRoles NOTIFY rolesChanged)
    Q_CLASSINFO("DefaultProperty", "items")

    TreeModel(QObject *parent = Q_NULLPTR);
    ~TreeModel() override;

    QHash<int, QByteArray> roleNames() const Q_DECL_OVERRIDE;
    QVariant data(const QModelIndex &index, int role) const Q_DECL_OVERRIDE;
    Qt::ItemFlags flags(const QModelIndex &index) const Q_DECL_OVERRIDE;
    QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
    QModelIndex parent(const QModelIndex &index) const Q_DECL_OVERRIDE;
    int rowCount(const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
    int columnCount(const QModelIndex &parent = QModelIndex()) const Q_DECL_OVERRIDE;
    QQmlListProperty<TreeElement> items();

    QVariantList roles() const;
    void setRoles(const QVariantList &roles);

    Q_INVOKABLE QModelIndex indexFromElement(TreeElement *item);
    Q_INVOKABLE bool insertElement(TreeElement *item, const QModelIndex &parent = QModelIndex(), int pos = -1);

    TreeElement *elementFromIndex(const QModelIndex &index) const;

private:
    TreeElement *m_root;
    QHash<int, QByteArray> m_roles;

signals:
    void rolesChanged();
};

如何从QML树视图模型中删除数据？

0 个答案: