Question

我正在学习在后台使用C ++编写QtQuick应用程序。我的计划是尽可能在QtQuick（QML）中编写代码，但有一件事我找不到，所以我决定使用C ++。基本上，我需要创建一个应用程序，为用户提供某些小部件和一个按钮。单击该按钮后，将创建并调用CLI命令。我可以使用javascript创建这个CLI命令，但是我找不到如何执行这个命令的方法，所以我决定使用C ++。

计划是在QML中的按钮上注册信号，并将此信号与C ++中的插槽连接。我打开了QML文档，在那里我找到了几个有用的例子。我的测试应用程序代码包含两个源文件：

main.qml：

import QtQuick 2.4
import QtQuick.Controls 1.3
import QtQuick.Window 2.2
import QtQuick.Dialogs 1.2
import QtQuick.Layouts 1.1
import "scripts.js" as Logic


ApplicationWindow {
    title: qsTr("Hello World")
    width: 640
    height: 480
    visible: true
    minimumHeight: 480
    minimumWidth: 640


    ColumnLayout{
        spacing: 2
        height: parent.height - 100
        width: parent.width

        GridLayout {
            id: grid
            columns: 3

            Label { text: "Vstupni soubor";  }
            TextField {
                id: input_file_field
            }
            Button {
                text: "..."
                onClicked: fileDialogInputFile.open()
            }


            Label { text: "Vystupni adresar";  }
            TextField {id: output_dir_field}
            Button {
                text: "..."
                onClicked: fileDialogOutputDir.open()
            }

            CheckBox{
                id: opt1
                text: "Volba 1"
            }

            CheckBox{
                id: opt2
                text: "Volba 2"
            }

            CheckBox{
                id: opt3
                text: "Volba 3"
            }

        }

        Button {

            signal qmlSignal(string msg)
            objectName: "myButton"

            text: "Analyzuj"
            onClicked: {
                qmlSignal("Hello from QML")
                console.log("Nahodne cislo " + Logic.func())
            }
        }

    }


    TextArea {
        id: log_output
        width: parent.width
        height: 100
        y: parent.height - 100
        readOnly: true
        text: "Log zprav";
    }

    FileDialog {
        id: fileDialogInputFile
        title: "Please choose a file"
        onAccepted: {
            input_file_field.text = fileDialogInputFile.fileUrl
        }
    }

    FileDialog {
        id: fileDialogOutputDir
        title: "Please select output directory"
        selectFolder: true
        onAccepted: {
            output_dir_field.text = fileDialogOutputDir.fileUrl
            console.log("You chose: " + fileDialogOutputDir.fileUrl)
        }
    }


}

main.cpp中：

#include <QApplication>
#include <QQmlApplicationEngine>
#include <QDebug>
#include <QObject>

class MyClass : public QObject
{
    Q_OBJECT

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


int main(int argc, char *argv[]) {
    qDebug() << "Hello World - main!";

    QGuiApplication app(argc, argv);

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

    MyClass myClass;
    QObject *win = engine.rootObjects()[0];
    QObject *item = win->findChild<QObject*>("myButton");

    QObject::connect(item, SIGNAL(qmlSignal(QString)),
                     &myClass, SLOT(cppSlot(QString)));

    return app.exec();
}

可以编译和运行程序。当我运行程序时，我可以在控制台上看到这个：

QML debugging is enabled. Only use this in a safe environment.
Hello World - main!
QObject::connect: No such slot MyClass::cppSlot(QString) in ../pokus/main.cpp:30
QObject::connect:  (sender name:   'myButton')

这意味着，程序正在运行，但无法将cppSlot连接到我的按钮生成的信号上。我遇到的问题是我遵循了QML手册，博客处理了最复杂的问题，即我花了一天的谷歌搜索没有任何结果..

Answer 1

您的代码无法编译：

debug/main.o: In function `MyClass::MyClass()':
/home/micurtis/dev/test/guitest/main.cpp:6: undefined reference to `vtable for MyClass'

如果我#include "main.moc"并删除对Logic.js的引用，当我点击“Analyzuj”时它对我有用：

    // ...
    return app.exec();
}

#include "main.moc"

输出：

Starting /home/micurtis/dev/test/guitest/guitest...
QML debugging is enabled. Only use this in a safe environment.
Hello World - main!
Called the C++ slot with message: "Hello from QML"
/home/micurtis/dev/test/guitest/guitest exited with code 0

QtQuick应用程序和C ++插槽绑定错误

1 个答案: