无法在QML中使用C++ QQuickPaintedItem单例

#include <QQuickPaintedItem>
#include <QPainter>

class MyPaintedItem : public QQuickPaintedItem
{
    Q_OBJECT
public:
    static MyPaintedItem* instance();

    void paint(QPainter* painter) override;
};

MyPaintedItem* MyPaintedItem::instance()
{
    static MyPaintedItem item;
    return &item;
}

void MyPaintedItem::paint(QPainter* painter)
{
    // 绘制逻辑
    painter->drawRect(boundingRect());
}

#include <QQmlEngine>
#include <QQmlContext>

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlEngine engine;
    MyPaintedItem* item = MyPaintedItem::instance();
    engine.rootContext()->setContextProperty("MyPaintedItem", item);

    // 加载QML文件并显示界面
    QQmlComponent component(&engine, QUrl("main.qml"));
    QObject* rootObject = component.create();
    // ...

    return app.exec();
}

import QtQuick 2.0

Item {
    width: 200
    height: 200

    MyPaintedItem {
        id: paintedItem
        anchors.fill: parent
    }

    // 其他QML代码
}