[英]How does setContextProperty() fail in this situation?
我在C ++中创建了三个类,分别是Window,PropertyList和MyParams,我想将PropertyList和MyParams这两个类传递给qml。
class Window
{
public:
PropertyList* getPropertyList();
private:
PropertyList* propertyList;
};
class PropertyList : public QObject
{
Q_OBJECT
public:
MyParams* getMyParams();
Q_INVOKABLE void test();
private:
MyParams* myParams;
};
class MyParams : public QObject
{
Q_OBJECT
public:
Q_INVOKABLE void test();
};
int main(int argc, char *argv[])
{
Window* window = new Window();
PropertyList* propertyList = window->getPropertyList();
MyParams* myParam = propertyList->getMyParams();
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty(QStringLiteral("myParams"), myParam);
engine.rootContext()->setContextProperty(QStringLiteral("propertyList"), propertyList);
}
为什么这样做:
engine.rootContext()->setContextProperty(QStringLiteral("propertyList"), propertyList);
这失败了:
engine.rootContext()->setContextProperty(QStringLiteral("myParams"), myParam);
是因为我将PropertyList声明为Q_OBJECT吗? 我该如何解决呢? 非常感谢。
可以成功调用propertyList.test(),而无法调用myParams.test()并使qml崩溃。
我在您的代码示例中看不到任何问题,因为示例不完整(请考虑: https : //stackoverflow.com/help/reprex )。
不过,我为您实施了一个解决方案。 希望对您有所帮助。 ( 警告 :类Window
周围会发生内存泄漏,但是它应该有助于理解C ++和Qml绑定)
这是您的PropertyList.h
:
#ifndef PROPERTYLIST_H
#define PROPERTYLIST_H
#include "myparams.h"
#include <QObject>
class PropertyList : public QObject
{
Q_OBJECT
public:
explicit PropertyList(QObject *parent = nullptr) : QObject (parent) { }
MyParams* getMyParams()
{
return myParams;
}
Q_INVOKABLE void test()
{
qDebug() << "PropertyList test";
}
private:
MyParams* myParams = new MyParams();
};
#endif // PROPERTYLIST_H
这是您的MyParams.h
:
#ifndef MYPARAMS_H
#define MYPARAMS_H
#include <QObject>
#include <QDebug>
class MyParams : public QObject
{
Q_OBJECT
public:
explicit MyParams(QObject *parent = nullptr) : QObject (parent) { }
Q_INVOKABLE void test()
{
qDebug() << "MyParams test";
}
};
#endif // MYPARAMS_H
这是您的main.cpp
:
#include "propertylist.h"
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QQmlEngine>
#include <QQmlContext>
#include <QDebug>
class Window
{
public:
PropertyList* getPropertyList()
{
return propertyList;
}
private:
PropertyList* propertyList = new PropertyList(nullptr);
};
int main(int argc, char *argv[])
{
QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
Window* window = new Window();
PropertyList* propertyList = window->getPropertyList();
MyParams* myParam = propertyList->getMyParams();
QQmlApplicationEngine engine;
engine.rootContext()->setContextProperty(QStringLiteral("myParams"), myParam);
engine.rootContext()->setContextProperty(QStringLiteral("propertyList"), propertyList);
engine.load(QUrl(QStringLiteral("qrc:/main.qml")));
if (engine.rootObjects().isEmpty())
{
return -1;
}
return app.exec();
}
这是您的main.qml
:
import QtQuick 2.9
import QtQuick.Window 2.2
import QtQuick.Controls 2.0
import QtQuick.Layouts 1.0
Window {
visible: true
width: 640
height: 480
title: qsTr("Hello World")
ColumnLayout {
anchors.centerIn: parent
Button {
text: "myParams"
onClicked: {
myParams.test()
}
}
Button {
text: "propertyList"
onClicked: {
propertyList.test()
}
}
}
}
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