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如何修复“创建的图形对象未放置在图形场景中”的错误

qwidget qt5 qml qt c++

mike510a · 技术社区 · 8 年前

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上

在这样做的过程中,我遇到了以下错误:

QQmlComponent:创建的图形对象未放置在图形中场景

之后是:

程序意外完成。

以下是我试图创建特殊QQuickPaintedItem的上下文以及它的源代码:

主要的qml公司

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公司

#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());

}

主要的cpp公司

#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();
}

预期结果是在QML场景图上绘制一个按钮有人知道我如何使用某种方法来实现这一点吗?(我知道Qt不支持它,但我正在尝试实现一种方法来实现它,所以不要同时使用“你不能”的答案,因为我确信有一种方法。

1 回复 | 直到 8 年前

JustWe 8 年前

预期结果是在QML场景图上绘制一个按钮

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;
};