我正在尝试在Qml引擎中注册JB_NodeModel。 我收到此错误：

“对隐式删除的qqmlElement（JB_NodeModel）的默认构造函数的调用-隐式删除了qqmlElement（JB_NodeModel）的默认构造函数，因为基类JB_NodeModel没有默认构造函数。”

但是我看不到默认构造函数有问题。 任何帮助将不胜感激。

我使用了初始化程序列表，但似乎无济于事。

这是JB_NodeModel.h的简化版本：

class SP3CORESHARED_EXPORT JB_NodeModel : public QAbstractItemModel
{
    Q_OBJECT
public:
 explicit JB_NodeModel(QObject *parent = nullptr);

~JB_NodeModel();

protected:
    JB_Node* rootNode;
    JB_Node* actingRootNode;
    bool isValidURL(QString fieldName,JB_Node* node) const;

    QVector<QString> columnHeadingsV;    
    QHash<int,QVector<QString>> mapped_dbFieldNamesH;    
    QList<QString> unEditableDBFieldNamesList;
    QList<QString> editableCheckBoxDBFieldNamesList; 

private:
    JB_DatabaseManager& mDB;
    int jobID;
    int numOfLevels;
    QSharedPointer<JB_NodeModelHelpProt> nodeModelHelper;
    QVector<QSharedPointer<QHash<QString,JB_Node*>>> nodesHV;     
    QVector<JB_Node*> alteredNodesV;
    bool isTreeModel;
    bool canEmitDataChanged;

 };

这是JB_NodeModel.cpp构造函数的来源：

JB_NodeModel::JB_NodeModel(QObject *parent)
: QAbstractItemModel(parent),rootNode(nullptr),actingRootNode(nullptr),mDB(JB_DatabaseManager::instance()),jobID(aJobID),numOfLevels(1),nodeModelHelper(nullptr),isTreeModel(true),canEmitDataChanged(true),dragDropHelper(false)
{
    QSharedPointer<JB_NodeModelHelpProt> aNodeModelHelper(new JB_NodeModHelp_TreeGrpPers());
    nodeModelHelper = aNodeModelHelper;

    canEmitDataChanged = true;
    dragDropHelper = false;

    Q_ASSERT(!nodeModelHelper.isnull());

    alteredNodesV.clear();

    rootNode = nullptr;
    actingRootNode = nullptr;

等

这是在QML引擎中注册：

QGuiApplication app(argc,argv);

qmlRegisterType<JB_NodeModel>("JB_NodeModel",1,"JB_NodeModel");


qqmlApplicationEngine engine;

const QUrl url(QStringLiteral("qrc:/main.qml"));
QObject::connect(&engine,&qqmlApplicationEngine::objectCreated,&app,[url](QObject *obj,const QUrl &objUrl) {
    if (!obj && url == objUrl)
        QCoreApplication::exit(-1);
},Qt::QueuedConnection);
engine.load(url);

这是qqmlprivate.h有关qqmlElement的相关部分：

class QJSEngine;
class qqmlEngine;
class qqmlCustomParser;
namespace qqmlPrivate
{
    void Q_QML_EXPORT qdeclarativeelement_destructor(QObject *);
    template<typename T>
    class qqmlElement final : public T
{
public:
    ~qqmlElement() override {
        qqmlPrivate::qdeclarativeelement_destructor(this);
    }
    static void operator delete(void *ptr) {
        // We allocate memory from this class in qqmlType::create
        // along with some additional memory.
        // So we override the operator delete in order to avoid the
        // sized operator delete to be called with a different size than
        // the size that was allocated.
        ::operator delete (ptr);
    }
    static void operator delete(void *,void *) {
        // Deliberately empty placement delete operator.
        // Silences MSVC warning C4291: no matching operator delete found
    }
};


template<typename T>

//错误发生在下一行

void createInto(void *memory) { new (memory) qqmlElement<T>; }

template<typename T>
QObject *createParent(QObject *p) { return new T(p); }