c++ - C++和QML之间的通信

此page显示了如何从QML内调用C++函数。

我要做的是通过C++函数更改按钮上的图像(触发状态更改或完成更改)。

我该如何实现？

更新

我尝试了Radon的方法，但是当我插入以下行时:

    QObject *test = dynamic_cast<QObject *>(viewer.rootObject());

编译器提示如下:

    error: cannot dynamic_cast '((QMLCppBinder*)this)->QMLCppBinder::viewer.QDeclarativeView::rootObject()' (of type 'struct QGraphicsObject*') to type 'class QObject*' (source is a pointer to incomplete type)

如果相关，QMLCppBinder是我尝试构建的类，以封装从多个QML页面到C++代码的连接。这似乎比人们预期的要复杂。

这是一个骨架类，为此提供了一些上下文:

    class QMLCppBinder : public QObject
    {
        Q_OBJECT
    public:
        QDeclarativeView viewer;

        QMLCppBinder() {
            viewer.setSource(QUrl("qml/Connect/main.qml"));
            viewer.showFullScreen();
            // ERROR
            QObject *test = dynamic_cast<QObject *>(viewer.rootObject());
        }
    }

最佳答案

如果为图像设置了objectName，则可以很容易地从C++访问它:

main.qml

import QtQuick 1.0

Rectangle {
    height: 100; width: 100

    Image {
        objectName: "theImage"
    }
}

C++中的:

// [...]

QDeclarativeView view(QUrl("main.qml"));
view.show();

// get root object
QObject *rootObject = dynamic_cast<QObject *>(view.rootObject());

// find element by name
QObject *image = rootObject->findChild<QObject *>(QString("theImage"));

if (image) { // element found
    image->setProperty("source", QString("path/to/image"));
} else {
    qDebug() << "'theImage' not found";
}

// [...]

→QObject.findChild()，QObject.setProperty()