Qt Communication between QML and C++ Call C++ in QML
Example
Register C++ classes in QML
At C++ side, imagine we have a class named QmlCppBridge, it implements a method called printHello().
class QmlCppBridge : public QObject
{
Q_OBJECT
public:
Q_INVOKABLE static void printHello() {
qDebug() << "Hello, QML!";
}
};
We want to use it in QML side. We should register the class by calling qmlRegisterType():
// Register C++ class as a QML module, 1 & 0 are the major and minor version of the QML module
qmlRegisterType<QmlCppBridge>("QmlCppBridge", 1, 0, "QmlCppBridge");
In QML, use following code to call it:
import QmlCppBridge 1.0 // Import this module, so we can use it in our QML script
QmlCppBridge {
id: bridge
}
bridge.printHello();
Using QQmlContext to inject C++ classes or variables to QML
We still use the C++ class in previous example:
QQmlApplicationEngine engine;
QQmlContext *context = engine.rootContext();
// Inject C++ class to QML
context->setContextProperty(QStringLiteral("qmlCppBridge"), new QmlCppBridge(&engine));
// Inject C++ variable to QML
QString demoStr = QStringLiteral("demo");
context->setContextProperty(QStringLiteral("demoStr"), demoStr);
At QML side:
qmlCppBridge.printHello(); // Call to C++ function
str: demoStr // Fetch value of C++ variable
Note: This example is based on Qt 5.7. Not sure if it fits earlier Qt versions.
