Question

我有一个奇怪的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QWidget派生类（QPushButton）的整体外观，然后将其绘制到QQuickPaintedItem

这样做我遇到了这个错误：

QQmlComponent：创建的图形对象未放置在图形中场景。

其次是：

该程序意外结束。

以下是我试图创建我的特殊QQuickPaintedItem以及它的源代码的上下文：

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());

}

的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();
}

预期结果是绘制到QML场景图上的按钮有谁知道如何使用某种方法实现这一目标？（我知道它不受Qt的支持，但是我试图实现一种方法来实现它，所以不要同时使用“你不能”的答案，因为有一种方式我确定。

Answer 1

预期结果是在QML场景图上绘制了一个按钮

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;
};

如何修复错误，说明创建的图形对象未放置在图形场景中

main.qml

widgetInterface.h

widgetinterface.cpp

的main.cpp

1 个答案: