如何修复“Created graphical object was not placed in the graphics scene”的错误

Question

我有一个 st运行ge 错误是由一个看似简单的问题引起的。

在我的源代码中，我试图使用 QQuickPaintedItem 来渲染派生的 QWidget class (QPushButton) 的整体外观，然后将其绘制到 QQuickPaintedItem

在这样做的过程中，我运行遇到了这个错误：

QQmlComponent: Created graphical object was not placed in the graphics scene.

其次是：

The program has unexpectedly finished.

这是我试图创建我的特殊 QQuickPaintedItem 的上下文及其源代码：

main.qml

import QtQuick 2.9
import com.particletool 1.0
import QtQuick.Particles 2.0
import QtQuick.Window 2.3
import QtQuick.Controls 2.2
import QtQuick.Dialogs 1.2
import QtQuick.Controls 1.4 as QQ1
  Item {
     id: root
     width: Screen.width
     height: Screen.height
     WidgetInterface {
        id: w
     }
   }

widgetInterface.h

#ifndef WIDGETINTERFACE_H
#define WIDGETINTERFACE_H

#include <QObject>
#include <QQuickItem>
#include <QQuickPaintedItem>
#include <QWidget>
#include <QPushButton>
#include <QtQuick>
class WidgetInterface : public QQuickPaintedItem
{
public:
    WidgetInterface(QQuickItem *parent = nullptr, QWidget* renderWidget = nullptr);
    QWidget* m_widget;
    QPushButton* m_button;
protected:
    void paint(QPainter* painter);
public slots:
   void morphIntoButton(QString txt);
};

#endif // WIDGETINTERFACE_H

widgetinterface.cpp

#include "widgetinterface.h"
#include <QQuickPaintedItem>
#include <QObject>
#include <QPainter>
#include <QWidget>
#include <QPushButton>
WidgetInterface::WidgetInterface(QQuickItem *parent, QWidget* renderWidget) : QQuickPaintedItem(parent), m_widget(renderWidget)
{
    morphIntoButton("test");
    QQmlEngine::setObjectOwnership(m_button, QQmlEngine::JavaScriptOwnership);
}

void WidgetInterface::paint(QPainter *painter)
{
    if (m_widget != nullptr) {
        painter->end();
        m_button->render(painter);

    } else {

    }
}


void WidgetInterface::morphIntoButton(QString txt)
{
    m_widget->setGeometry(0,0, this->width(), this->height());

    m_button = new QPushButton(m_widget);
    m_button->setGeometry(m_widget->geometry());
    m_button->setText(txt);
    this->update(this->boundingRect().toRect());

}

main.cpp

#include <QtGui/QGuiApplication>
#include <QApplication>
#include <QtQml/QQmlApplicationEngine>
#include "src/interfaces/widgetinterface.h"
int main(int argc, char *argv[])
{
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);

    QGuiApplication app(argc, argv);


    QQmlApplicationEngine engine;

      qmlRegisterType<WidgetInterface>("com.particletool", 1, 0, "WidgetInterface");

    engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
    if (engine.rootObjects().isEmpty())
        return -1;

    return app.exec();
}

预期的结果是在 QML 场景图上绘制了一个按钮有谁知道我如何使用某种方法实现这一目标？（我知道 Qt 不支持它，但我正在尝试实现一种实现它的方法，所以不要同时使用 "You can't" 答案，因为我确定有一种方法。

Answer 1

The expected result is a button being drawn on to the QML scene graph

class WidgetInterface : public QQuickPaintedItem
{
public:
    WidgetInterface(QQuickItem *parent = Q_NULLPTR) :
        QQuickPaintedItem(parent)
    {
        mButton = new QPushButton("TEST", Q_NULLPTR);
        auto resize = [=](){
            mButton->setGeometry(QRect(QPoint(), boundingRect().size().toSize()));
            QPixmap p(mButton->size());
            mButton->render(&p);
            if(!p.isNull())
                mButtonPix = p;
            update();
        };
        connect(this, &QQuickPaintedItem::widthChanged,  this, resize, Qt::QueuedConnection);
        connect(this, &QQuickPaintedItem::heightChanged, this, resize, Qt::QueuedConnection);
    }
    ~WidgetInterface() {
        mButton->deleteLater();
    }
protected:
    void paint(QPainter* painter){
        painter->drawPixmap(0, 0, mButtonPix);
    }
private:
    QPushButton* mButton;
    QPixmap      mButtonPix;
};

如何修复“Created graphical object was not placed in the graphics scene”的错误

How can I fix the error saying Created graphical object was not placed in the graphics scene

c++

qt

qwidget

qml

qt5

main.qml

widgetInterface.h

widgetinterface.cpp

main.cpp