从QML ListView处理QAbstractListModel中的数据

Question

我有一个QML ListView,它使用QAbstractListModel子类作为模型.

ListView {
    id: myListView
    x: 208
    y: 19
    width: 110
    height: 160
    delegate: myListDelegate {}
    model: MyListModel
    opacity: 0
}

该模型是MyListItems 的列表.

class MyListModel : public QAbstractListModel
{
    Q_OBJECT
public:
    enum MyRoles {
        HeadingRole = Qt::UserRole + 1,
        DescriptionRole,
        QuantityRole
    };

    explicit MyListModel(QObject *parent = 0);

    void addMyListItem(const MyListItem &item);
    int rowCount(const QModelIndex & parent = QModelIndex()) const;
    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const;
    void dropList();

private:
    QList<MyListItem> m_list;

};

在代表中,我有一个鼠标区.

我怎么可以拦截在鼠标区域点击,并挑选这 MyListItem从我的QList模型和地方发送它的应用程序的C++部分里面？

Answer 1

评论提到返回指向MyListItemfrom data()到QML 的指针,并在QML中访问和修改它.这需要您MyListItem继承QObject并Q_PROPERTY为要在QML中访问的每个成员添加一个.它还需要密切关注对象所有权(QQmlEngine::ObjectOwnership).

还有另一种方法:实现QAbstractListModel::setData()和QAbstractListModel::roleNames(),模型内容可以从QML更改,如model.roleName = foo.

下面的最小工作示例,每次单击代表时数量加倍:

C++:

struct MyListItem
{
    QString heading;
    QString description;
    int quantity;
};

class MyListModel : public QAbstractListModel
{
    Q_OBJECT
    Q_ENUMS(MyRoles)
public:
    enum MyRoles {
        HeadingRole = Qt::UserRole + 1,
        DescriptionRole,
        QuantityRole
    };

    using QAbstractListModel::QAbstractListModel;

    QHash<int,QByteArray> roleNames() const override {
        return { { HeadingRole, "heading" },
            { DescriptionRole, "description" },
            { QuantityRole, "quantity" },
        };
    }
    int rowCount(const QModelIndex & parent = QModelIndex()) const override {
        if (parent.isValid())
            return 0;
        return m_list.size();
    }

    bool setData(const QModelIndex &index, const QVariant &value, int role) override
    {
        if (!hasIndex(index.row(), index.column(), index.parent()) || !value.isValid())
            return false;

        MyListItem &item = m_list[index.row()];
        if (role == DescriptionRole) item.description = value.toString();
        else if (role == HeadingRole) item.heading = value.toString();
        else if (role == QuantityRole) item.quantity = value.toInt();
        else return false;

        emit dataChanged(index, index, { role } );

        return true ;

    }

    QVariant data(const QModelIndex & index, int role = Qt::DisplayRole) const override {
        if (!hasIndex(index.row(), index.column(), index.parent()))
            return {};

        const MyListItem &item = m_list.at(index.row());
        if (role == DescriptionRole) return item.description;
        if (role == HeadingRole) return item.heading;
        if (role == QuantityRole) return item.quantity;

        return {};
    }

private:
    QVector<MyListItem> m_list = {
        { "heading 1", "description 1", 1 },
        { "heading 2", "description 2", 42 },
        { "heading 3", "description 3", 4711 }
    };
};

QML:

ListView {
    id: listView
    anchors.fill: parent
    model: MyListModel {}

    delegate: Item {
        implicitHeight: text.height
        width: listView.width
        Text {
            id: text
            text: model.heading + " " + model.description + " " + model.quantity
        }

        MouseArea {
            anchors.fill: text
            onClicked: {
                model.quantity *= 2;
            }
        }
    }
}

Answer 2

您还可以使用index委托中的属性来操作数据。您只需要QModelIndex使用模型上的 index 方法将 QML 索引转换为 a 。这是一个简单的示例，每次单击列表项时，我们将显示值更改为字符串“3”。

ListView {
    id: listView
    anchors.fill: parent
    model: my_model

    delegate: Rectangle {
        height: 50
        width: listView.width

        MouseArea {
            anchors.fill: parent
            onClicked: {
                // Column is always zero as it's a list
                var column_number = 0; 
                // get `QModelIndex`
                var q_model_index = my_model.index(index, column_number);

                // see for list of roles: 
                // http://doc.qt.io/qt-5/qabstractitemmodel.html#roleNames
                var role = 1

                var data_changed = my_model.setData(q_model_index, "3", role);

                console.log("data change successful?", data_changed);
            }
        }
    }
}

除了index委托中的属性外，所有默认角色名称都在委托中可用。例如，我之前使用过decoration角色来设置color我的Rectangle委托的属性。请参阅此列表了解更多信息。

ListView {
    delegate: Rectangle {
        // list items have access to all default `roleNames` 
        // in addition to the `index` property.
        // For example, using the decoration role, demo'd below
        color: decoration
    }
}

另请参阅此链接，其中 Mitch Curtis 建议使用 qmlRegisterUncreatableType 来注册用户枚举。