C++使用信号槽进行QML

Question

我有一个小班不能正常工作,我不知道它有什么问题.编译器给出了以下消息:

main.cpp: error: undefined reference to 'CDetails::CDetails()'

这是代码中的快照:

//main.cpp
#include <QtGui/QGuiApplication>
#include "qtquick2applicationviewer.h"
#include <QQmlContext>
#include <QDebug>

class CDetails : public QObject
{   Q_OBJECT
    public:
        CDetails() {}
        ~CDetails(void) {}


    public slots:
        void cppSlot(const QString &msg)
        {    qDebug() << "Called the C++ slot with message:" << msg;
        }
};

int main(int argc, char *argv[])
{   QGuiApplication app(argc, argv);
    QtQuick2ApplicationViewer viewer;
    viewer.setMainQmlFile(QStringLiteral("qml/testqml/main.qml"));
    viewer.showExpanded();

    CDetails *test = new CDetails();
    QObject::connect((QObject*)viewer.rootObject(),
                 SIGNAL(qmlSignal(QString)),test,
                 SLOT(cppSlot(QString)));
    return app.exec();
}

在main.qml中:

import QtQuick 2.0
Rectangle {
    id: guide
    width: 360
    height: 360
    signal qmlSignal(string msg)
    Text {
        text: qsTr("Hello World")
        anchors.centerIn: parent
    }
    property double scaleFactor: 1.0
    property string iconUrl: "image.png"
    MouseArea {
        anchors.fill: parent
        onClicked: {
            guide.qmlSignal("Hello from QML")
        }
    }
}

更新:感谢关于构造函数的建议.现在的错误是:

error: undefined reference to 'vtable for CDetails'

在这里错过了什么？欢迎所有建议.

Answer 1

错误:未定义引用'vtable for CDetails'

在这里错过了什么？欢迎所有建议.

似乎你在主要功能之前缺少moc include.

main.cpp中

#include <QtGui/QGuiApplication>
#include <QQmlContext>
#include <QDebug>

class CDetails : public QObject
{   Q_OBJECT
    public:
        CDetails() {}
        ~CDetails(void) {}


    public slots:
        void cppSlot(const QString &msg)
        {    qDebug() << "Called the C++ slot with message:" << msg;
        }
};

#include "main.moc"

int main(int argc, char *argv[])
{   QGuiApplication app(argc, argv);
    QQuickView view;
    viewer.setMainQmlFile(QStringLiteral("qml/testqml/main.qml"));
    viewer.showExpanded();

    CDetails *test = new CDetails();
    QObject::connect((QObject*)viewer.rootObject(),
                 SIGNAL(qmlSignal(QString)),test,
                 SLOT(cppSlot(QString)));
    return app.exec();
}

main.pro

...
TEMPLATE = app
TARGET = main
QT += quick
SOURCES += main.cpp
...

请注意,您还需要添加之前的自定义行,例如处理应用程序查看器等.

或者,您也可以将类和main.cpp分离,这意味着您将类的声明放入单独的标头中,然后将defintition放入单独的源文件中.

main.cpp将包含新建立的标头,您需要确保将新标头和源文件分别添加到qmake项目文件中HEADERS的SOURCES变量,以完成moc处理.

Answer 2

您缺少构造函数和析构函数的实现。快速解决：

class CDetails : public QObject
{   Q_OBJECT
public:
  CDetails() {}
  ~CDetails(void) {}
   ...
};