QML與C++幾種交互方式

更新時(shí)間：2024年04月30日 08:48:38 作者：狗蛋兒l

QML作為構(gòu)建界面的語(yǔ)言是非常簡(jiǎn)潔的,但是界面的后臺(tái)有些時(shí)候是經(jīng)常要與C++交互的,本文主要介紹了QML與C++幾種交互方式,感興趣的可以了解一下

QML調(diào)用CPP函數(shù)

要求：

使用 Q_OBJECT 宏需要繼承 QObject 類。Q_OBJECT能夠啟用信號(hào)和槽機(jī)制、使用動(dòng)態(tài)屬性系統(tǒng)。（使用 Q_OBJECT 宏的類需要通過Qt的元對(duì)象編譯器（moc）進(jìn)行處理。）
使用 Q_INVOKABLE 修飾要暴露給 QML 的函數(shù)。

1.在main.cpp中進(jìn)行注冊(cè)

 // 注冊(cè)c++類到qml  參數(shù)分別為導(dǎo)入的 模塊名稱  主版本號(hào)  次版本號(hào)  模塊名稱
 qmlRegisterType<CppObject>("CppObject",1,0,"CppObject");

2.在qml中導(dǎo)入

import CppObject 1.0
 CppObject{
       id:cppobj
   }

3.通過id+方法名的方式調(diào)用

   // 加上這個(gè)宏，當(dāng)前函數(shù)就可以被qml訪問調(diào)用
    Q_INVOKABLE void func();

//test.h
#ifndef TEST_H
#define TEST_H

#include <QObject>
#include "QDebug"
class CppObject : public QObject
{
    Q_OBJECT
public:
    explicit CppObject(QObject *parent = nullptr);
    //通過宏定義在qml使用cpp類中的函數(shù)
    Q_INVOKABLE void print_(QString str)
    {
        qDebug()  << str;
    }

};
#endif // TEST_H

//main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include <QLocale>
#include <QTranslator>
#include "test.h"
int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
    QGuiApplication app(argc, argv);

    QTranslator translator;
    const QStringList uiLanguages = QLocale::system().uiLanguages();
    for (const QString &locale : uiLanguages) {
        const QString baseName = "untitled_" + QLocale(locale).name();
        if (translator.load(":/i18n/" + baseName)) {
            app.installTranslator(&translator);
            break;
        }
    }

	//主要是這里其他的都是默認(rèn)的
    // 注冊(cè)c++類到qml  參數(shù)分別為導(dǎo)入的 模塊名稱  主版本號(hào)  次版本號(hào)  模塊名稱
    qmlRegisterType<CppObject>("CppObject",1,0,"CppObject");



    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(
        &engine,
        &QQmlApplicationEngine::objectCreated,
        &app,
        [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        },
        Qt::QueuedConnection);
    engine.load(url);

    return app.exec();
}

//main.qml
import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
import CppObject 1.0

Window {
    id: win
    width: 800
    height: 600
    visible: true
    title: qsTr("Hello World")

    CppObject{
            id:cppobj
        }

    Button{
            width: 50
            height: 50
            background: Rectangle{
                color:"red"
            }
            onClicked: {
                //obj.printMsg()
                cppobj.print_("test")
            }
        }

}

定義全局變量，注冊(cè)到上下文

樣例：

#include <QQmlContext>
QQmlApplicationEngine engine;
//這兩句是重點(diǎn)，設(shè)置全局變量
QQmlContext *context = engine.rootContext();
context->setContextProperty("SCREEN_WIDTH", 800);

也可以用此方法將類對(duì)象暴露給QMLsetContextProperty兩個(gè)參數(shù)表示的意義為:

第一個(gè)參數(shù)表示 qml 可以識(shí)別的對(duì)象名
第二個(gè)參數(shù)表示 C++ 對(duì)象

#include <QtQml/QQmlContext>
#include "vacUdpClient.h"
 
/*** main.cpp ***/
vacUdpClient udpclient;
QQmlContext* context = engine.rootContext();
context->setContextProperty("udpclient", &udpclient);

使用時(shí)候當(dāng)變量用就行，SCREEN_WIDTH為變量名

//main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QLocale>
#include <QTranslator>
//全局變量必須得頭文件
#include <QQmlContext>

int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
    QGuiApplication app(argc, argv);

    QTranslator translator;
    const QStringList uiLanguages = QLocale::system().uiLanguages();
    for (const QString &locale : uiLanguages) {
        const QString baseName = "untitled_" + QLocale(locale).name();
        if (translator.load(":/i18n/" + baseName)) {
            app.installTranslator(&translator);
            break;
        }
    }

    QQmlApplicationEngine engine;
    //這兩句是重點(diǎn)，設(shè)置全局變量
    QQmlContext *context = engine.rootContext();
    context->setContextProperty("SCREEN_WIDTH", 800);



    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(
        &engine,
        &QQmlApplicationEngine::objectCreated,
        &app,
        [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        },
        Qt::QueuedConnection);
    engine.load(url);
    return app.exec();
}

//main.qml
import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15
Window {
    id: window
    visible: true
    //使用全局變量
    width: SCREEN_WIDTH
    height: 500
    title: qsTr("Hello World")

    Button{
        width: 100
        height: 100
        background: {
            color:"black"
        }
    }
}

CPP訪問QML函數(shù)

//main.cpp
#include <QGuiApplication>
#include <QQmlApplicationEngine>
#include <QLocale>
#include <QTranslator>


int main(int argc, char *argv[])
{
#if QT_VERSION < QT_VERSION_CHECK(6, 0, 0)
    QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
#endif
    QGuiApplication app(argc, argv);

    QTranslator translator;
    const QStringList uiLanguages = QLocale::system().uiLanguages();
    for (const QString &locale : uiLanguages) {
        const QString baseName = "untitled_" + QLocale(locale).name();
        if (translator.load(":/i18n/" + baseName)) {
            app.installTranslator(&translator);
            break;
        }
    }

    QQmlApplicationEngine engine;
    const QUrl url(QStringLiteral("qrc:/main.qml"));
    QObject::connect(
        &engine,
        &QQmlApplicationEngine::objectCreated,
        &app,
        [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
                QCoreApplication::exit(-1);
        },
        Qt::QueuedConnection);
    engine.load(url);


    //重點(diǎn)
    auto list = engine.rootObjects();
    auto window = list.first();
    QVariant res;
    QVariant arg_1 = 123;
    QVariant arg_2 = "zhangsan";
    QMetaObject::invokeMethod(window, "qmlFunc",Q_RETURN_ARG(QVariant, res),Q_ARG(QVariant, arg_1),Q_ARG(QVariant, arg_2));

    qDebug() << "res = " << res;


    return app.exec();
}

//main.qml
import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15


Window {
    id: window
    visible: true
    width: SCREEN_WIDTH
    height: 500
    title: qsTr("Hello World")


    //供C++端調(diào)用的函數(shù)
    function qmlFunc(i, s) {
            return "success"
        }

   
}

單實(shí)例注冊(cè)類

main.cpp文件里加這個(gè)

 // qml單實(shí)例注冊(cè)
qmlRegisterSingletonInstance("PersonMudle", 1, 0, "MyPerson", &person);

以下這樣使用

import PersonMudle 1.0
	Button {
            objectName: "qml_button"
            text: "QML button"
            font.pixelSize: 25
 
            onClicked: {
                MyPerson.showInfo()
            }
        }

信號(hào)與槽

	//加在main.cpp中
   // engine 加載完成后 load以后
   auto list = engine.rootObjects();
   //auto objName = list.first()->objectName(); // 獲取第一個(gè)objname
   //auto mybuttonObj = list.first()->findChild<QObject *>("mybutton");
   auto window = list.first();
	
	//槽函數(shù)鏈接
	// 第一個(gè)參數(shù)為組件
	// 第二個(gè)為信號(hào)名
	// 第三個(gè)為類的實(shí)例化
	// 第三個(gè)為槽函數(shù)
   QObject::connect(window,SIGNAL(qmlSig(int,QString)),
                    CppObject::getInstance(),SLOT(cppSlot(int,QString)));

例子：

	//類
	Person person("張三", 18);
	//上下文: 將類對(duì)象注冊(cè)到QML的上下文背景中
    auto ctext = engine.rootContext();
    ctext->setContextProperty("OtPerson", &person);
 
    //cpp獲取qml中的指定對(duì)象
    auto rootObj = engine.rootObjects();
    // rootObj.first()獲取所有對(duì)象列表
    auto button = rootObj.first()->findChild<QObject*>("qml_button");
    // 使用QT4的方式綁定信號(hào)和槽： qml的信號(hào)，cpp的槽
    QObject::connect(button, SIGNAL(clicked()), &person, SLOT(clickButton()));
    QObject::connect(button, SIGNAL(coutNum(int)), &person, SLOT(clickCal(int)));
    /*
    // 使用QT5的方式綁定信號(hào)和槽不可行，此處button is nullptr
    auto button = rootObj.first()->findChild<QPushButton*>("qml_button");
    if (!button) {
        qDebug() << "button is nullptr";
    }
    QObject::connect(button, &QAbstractButton::clicked, &person, &Person::clieckButton);
    */

//main.qml
import QtQuick 2.15
import QtQuick.Window 2.15
import QtQuick.Controls 2.15 as QtCtrl
import QtQuick.Layouts 1.0
 
 
Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("qml和cpp交互總結(jié)")
 
    Item {
        id: item
        anchors.fill: parent
 
        QtCtrl.Button {
            objectName: "qml_button"
            text: "QML button"
            font.pixelSize: 25
            property int cal: 1
            // qml中自定義信號(hào)
            signal coutNum(int num)
 
            onClicked: {
                OtPerson.showInfo()
                if (0 == cal++ % 10) {
                    coutNum(cal)
                }
            }
        }
    }
 
}

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