如何将QML信号与C ++插槽连接? [英] How to connect a QML signal with a C++ slot?

问题描述

我在QML中的 MessageDialog 信号有问题.在我的 MessageDialog 中，有两个按钮分别表示是和否.我想用信号连接每个按钮.这是我的qml文件:

I have a problem with a MessageDialog signal in QML. In my MessageDialog I have two buttons for Yes and No. I want to connect each button with a signal. Here is my qml file:

import QtQuick 2.2
import QtQuick.Dialogs 1.1

Item{
    MessageDialog {
        signal qmlYesSig(string msg)
        signal qmlNoSig (string msg)
        title: "Send data?"
        icon: StandardIcon.Question
        text: "Do you want to save your data on the online platform?"
        detailedText: "Click Yes "
        standardButtons: StandardButton.Yes | StandardButton.No
        Component.onCompleted: visible = true
        onYes: qmlYesSig("From yes")
        onNo: qmlNoSig("From no")
    }
}

这是我的广告位:

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

这就是我在main中使用它的方式:

And here is how i use this in main:

QQuickView view(QUrl::fromLocalFile("window.qml"));
QObject *item = view.rootObject();
AddData myClass;
QObject::connect(item, SIGNAL(qmlSignal(QString)),
                 &myClass, SLOT(cppSlot(QString)));

view.show();

它给了我错误:

C2665:'QObject :: connect':3个重载都不能转换所有参数类型

C2665: 'QObject::connect': none of the 3 overloads could convert all the argument types

我已经尝试了很多次，但是我无法使QML信号和C ++插槽正常工作.我也尝试从这里 Qt doc 给出示例同样的错误.

I have try many times but I can't make work QML signal and C++ slots. Also I have try the example from here Qt doc and give me the same error.

有人可以告诉我如何为 MessageDialog 连接QML信号和C ++插槽吗?

Can somebody give me an idea how to connect QML signal and C++ slots for a MessageDialog?

推荐答案

您的QML文件是:

Item{
    MessageDialog {
        signal qmlYesSig(string msg)
        signal qmlNoSig (string msg)

        [...]
    }
}

您的C ++代码为:

QObject *item = view.rootObject();
AddData myClass;
QObject::connect(item, SIGNAL(qmlSignal(QString)),
                 &myClass, SLOT(cppSlot(QString)));

这意味着您正在QML文件的根项目中寻找一个名为"qmlSignal"的信号.这个根项目就是

It means that you are looking for a signal called "qmlSignal" in the root item of your QML file. This root item is simply

Item{}

如您所见，没有称为"qmlSignal"的信号.

As you can see, there is no signal called "qmlSignal".

您必须在根项中定义信号并从消息框中发出它.

You have to define the signal in the root item and emit it from the message box.

Item{
    signal qmlSignal(string msg)

    MessageDialog {
        onYes: parent.qmlSignal("From yes")
        onNo: parent.qmlSignal("From no")
    }
}

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