c++ - Qt - 单击 QML 按钮时如何运行 C++ 函数？使用 QQmlApplicationEngine

Question

myclass.h

#ifndef MYCLASS_H
#define MYCLASS_H

#include <QDebug>
#include <QObject>

class MyClass : public QObject
{
public:
    MyClass();

public slots:
    void buttonClicked();
    void buttonClicked(QString &in);
};

#endif // MYCLASS_H

---

myclass.cpp

#include "myclass.h"

MyClass::MyClass()
{
}

void MyClass::buttonClicked()
{
    // Do Something
}

void MyClass::buttonClicked(QString &in)
{
    qDebug() << in;
}

---

main.cpp

#include <QApplication>
#include <QQmlApplicationEngine>
#include <myclass.h>
#include <QQmlContext>

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

    QQmlApplicationEngine engine;
    engine.load(QUrl(QStringLiteral("qrc:///main.qml")));

    MyClass myClass;  // A class containing my functions

    // Trying to "SetContextProperty" as I saw people do it to achieve C++/QML connection
    QQmlContext * context = new QQmlContext(engine.rootContext());
    context->setContextProperty("_myClass", &myClass);

    return app.exec();
}

我想在 myClass 类中使用一个函数，该函数在单击 QML 按钮时采用 QString 参数..

当我编译并运行时......一切顺利。但是当我点击按钮时......它在调试器中显示了这个错误:

qrc:///main.qml:80: ReferenceError: _myClass is not defined

~> “我的 QML 文件中的第 80 行”:

74:    MouseArea {
75:        id: mouseArea1
76:        anchors.fill: parent
77:        hoverEnabled: true;
78:        onEntered: { rectangle1.border.width = 2 }
79:        onExited: { rectangle1.border.width = 1 }
80:        onClicked: _myClass.buttonClicked("Worked?")
81:    }

---

编辑:(至于导致编译错误的错误)

正如@Jairo所建议的，所有类都必须继承自QObject。

仍在寻找解决我的主要问题的方法。

Answer 1

呃哦。这里有几处错误。 (代码甚至可以编译吗？)

要事第一。将某些内容传递给 QML 引擎的根属性时，您无法创建新的上下文——您必须直接使用根上下文，如下所示:

engine.rootContext()->setContextProperty("_myClass", &myClass);

接下来，类定义有一些问题。在下面的代码中查看我的评论:

class MyClass : public QObject
{
    // This macro is required for QObject support.  You should get a compiler
    // error if you don't include this.
    Q_OBJECT

public:
    // QObjects are expected to support a parent/child hierarchy.  I've modified
    // the constructor to match the standard.
    explicit MyClass(QObject *parent = 0);

public slots:
    // This method needs to take either a QString or a const reference to one.
    // (QML doesn't support returning values via the parameter list.)
    void buttonClicked(const QString& in);
};

构造函数的实现应该将父类传递给基类:

MyClass::MyClass(QObject *parent) :
    QObject(parent)
{
}