实现QObject与JavaScript通讯(基于QWebEngine + QWebChannel)

实现QObject与JavaScript通讯(基于QWebEngine + QWebChannel)

通过使用QtWebEngine加载相关页面，然后用QtWebChannel作为Qt与Javascript交互通讯的桥梁；

1.Qt工程涉及profile文件QtJSInteract.pro

TEMPLATE = app
TARGET = QtJSConnect
INCLUDEPATH += .

QT += webenginewidgets webchannel

HEADERS += TMainWindow.h TInteractObject.h

SOURCES += main.cpp TMainWindow.cpp TInteractObject.cpp

RESOURCES += Resource.qrc

2.工程引用资源Resource.qrc

<!DOCTYPE RCC>
<RCC version="1.0">
  <qresource>
    <file>qwebchannel.js</file>
  </qresource>
</RCC>

其中qwebchannel.js是官方自动例子的js文件，可从Qt安装目录拷贝；

/****************************************************************************
**
** Copyright (C) 2015 The Qt Company Ltd.
** Copyright (C) 2014 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Milian Wolff <milian.wolff@kdab.com>
** Contact: http://www.qt.io/licensing/
**
** This file is part of the QtWebChannel module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL21$
** Commercial License Usage
** Licensees holding valid commercial Qt licenses may use this file in
** accordance with the commercial license agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and The Qt Company. For licensing terms
** and conditions see http://www.qt.io/terms-conditions. For further
** information use the contact form at http://www.qt.io/contact-us.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 or version 3 as published by the Free
** Software Foundation and appearing in the file LICENSE.LGPLv21 and
** LICENSE.LGPLv3 included in the packaging of this file. Please review the
** following information to ensure the GNU Lesser General Public License
** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** As a special exception, The Qt Company gives you certain additional
** rights. These rights are described in The Qt Company LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** $QT_END_LICENSE$
**
****************************************************************************/

"use strict";

var QWebChannelMessageTypes = {
    signal: 1,
    propertyUpdate: 2,
    init: 3,
    idle: 4,
    debug: 5,
    invokeMethod: 6,
    connectToSignal: 7,
    disconnectFromSignal: 8,
    setProperty: 9,
    response: 10,
};

var QWebChannel = function(transport, initCallback)
{
    if (typeof transport !== "object" || typeof transport.send !== "function") {
        console.error("The QWebChannel expects a transport object with a send function and onmessage callback property." +
                      " Given is: transport: " + typeof(transport) + ", transport.send: " + typeof(transport.send));
        return;
    }

    var channel = this;
    this.transport = transport;

    this.send = function(data)
    {
        if (typeof(data) !== "string") {
            data = JSON.stringify(data);
        }
        channel.transport.send(data);
    }

    this.transport.onmessage = function(message)
    {
        var data = message.data;
        if (typeof data === "string") {
            data = JSON.parse(data);
        }
        switch (data.type) {
            case QWebChannelMessageTypes.signal:
                channel.handleSignal(data);
                break;
            case QWebChannelMessageTypes.response:
                channel.handleResponse(data);
                break;
            case QWebChannelMessageTypes.propertyUpdate:
                channel.handlePropertyUpdate(data);
                break;
            default:
                console.error("invalid message received:", message.data);
                break;
        }
    }

    this.execCallbacks = {};
    this.execId = 0;
    this.exec = function(data, callback)
    {
        if (!callback) {
            // if no callback is given, send directly
            channel.send(data);
            return;
        }
        if (channel.execId === Number.MAX_VALUE) {
            // wrap
            channel.execId = Number.MIN_VALUE;
        }
        if (data.hasOwnProperty("id")) {
            console.error("Cannot exec message with property id: " + JSON.stringify(data));
            return;
        }
        data.id = channel.execId++;
        channel.execCallbacks[data.id] = callback;
        channel.send(data);
    };

    this.objects = {};

    this.handleSignal = function(message)
    {
        var object = channel.objects[message.object];
        if (object) {
            object.signalEmitted(message.signal, message.args);
        } else {
            console.warn("Unhandled signal: " + message.object + "::" + message.signal);
        }
    }

    this.handleResponse = function(message)
    {
        if (!message.hasOwnProperty("id")) {
            console.error("Invalid response message received: ", JSON.stringify(message));
            return;
        }
        channel.execCallbacks[message.id](message.data);
        delete channel.execCallbacks[message.id];
    }

    this.handlePropertyUpdate = function(message)
    {
        for (var i in message.data) {
            var data = message.data[i];
            var object = channel.objects[data.object];
            if (object) {
                object.propertyUpdate(data.signals, data.properties);
            } else {
                console.warn("Unhandled property update: " + data.object + "::" + data.signal);
            }
        }
        channel.exec({type: QWebChannelMessageTypes.idle});
    }

    this.debug = function(message)
    {
        channel.send({type: QWebChannelMessageTypes.debug, data: message});
    };

    channel.exec({type: QWebChannelMessageTypes.init}, function(data) {
        for (var objectName in data) {
            var object = new QObject(objectName, data[objectName], channel);
        }
        // now unwrap properties, which might reference other registered objects
        for (var objectName in channel.objects) {
            channel.objects[objectName].unwrapProperties();
        }
        if (initCallback) {
            initCallback(channel);
        }
        channel.exec({type: QWebChannelMessageTypes.idle});
    });
};

function QObject(name, data, webChannel)
{
    this.__id__ = name;
    webChannel.objects[name] = this;

    // List of callbacks that get invoked upon signal emission
    this.__objectSignals__ = {};

    // Cache of all properties, updated when a notify signal is emitted
    this.__propertyCache__ = {};

    var object = this;

    // ----------------------------------------------------------------------

    this.unwrapQObject = function(response)
    {
        if (response instanceof Array) {
            // support list of objects
            var ret = new Array(response.length);
            for (var i = 0; i < response.length; ++i) {
                ret[i] = object.unwrapQObject(response[i]);
            }
            return ret;
        }
        if (!response
            || !response["__QObject*__"]
            || response.id === undefined) {
            return response;
        }

        var objectId = response.id;
        if (webChannel.objects[objectId])
            return webChannel.objects[objectId];

        if (!response.data) {
            console.error("Cannot unwrap unknown QObject " + objectId + " without data.");
            return;
        }

        var qObject = new QObject( objectId, response.data, webChannel );
        qObject.destroyed.connect(function() {
            if (webChannel.objects[objectId] === qObject) {
                delete webChannel.objects[objectId];
                // reset the now deleted QObject to an empty {} object
                // just assigning {} though would not have the desired effect, but the
                // below also ensures all external references will see the empty map
                // NOTE: this detour is necessary to workaround QTBUG-40021
                var propertyNames = [];
                for (var propertyName in qObject) {
                    propertyNames.push(propertyName);
                }
                for (var idx in propertyNames) {
                    delete qObject[propertyNames[idx]];
                }
            }
        });
        // here we are already initialized, and thus must directly unwrap the properties
        qObject.unwrapProperties();
        return qObject;
    }

    this.unwrapProperties = function()
    {
        for (var propertyIdx in object.__propertyCache__) {
            object.__propertyCache__[propertyIdx] = object.unwrapQObject(object.__propertyCache__[propertyIdx]);
        }
    }

    function addSignal(signalData, isPropertyNotifySignal)
    {
        var signalName = signalData[0];
        var signalIndex = signalData[1];
        object[signalName] = {
            connect: function(callback) {
                if (typeof(callback) !== "function") {
                    console.error("Bad callback given to connect to signal " + signalName);
                    return;
                }

                object.__objectSignals__[signalIndex] = object.__objectSignals__[signalIndex] || [];
                object.__objectSignals__[signalIndex].push(callback);

                if (!isPropertyNotifySignal && signalName !== "destroyed") {
                    // only required for "pure" signals, handled separately for properties in propertyUpdate
                    // also note that we always get notified about the destroyed signal
                    webChannel.exec({
                        type: QWebChannelMessageTypes.connectToSignal,
                        object: object.__id__,
                        signal: signalIndex
                    });
                }
            },
            disconnect: function(callback) {
                if (typeof(callback) !== "function") {
                    console.error("Bad callback given to disconnect from signal " + signalName);
                    return;
                }
                object.__objectSignals__[signalIndex] = object.__objectSignals__[signalIndex] || [];
                var idx = object.__objectSignals__[signalIndex].indexOf(callback);
                if (idx === -1) {
                    console.error("Cannot find connection of signal " + signalName + " to " + callback.name);
                    return;
                }
                object.__objectSignals__[signalIndex].splice(idx, 1);
                if (!isPropertyNotifySignal && object.__objectSignals__[signalIndex].length === 0) {
                    // only required for "pure" signals, handled separately for properties in propertyUpdate
                    webChannel.exec({
                        type: QWebChannelMessageTypes.disconnectFromSignal,
                        object: object.__id__,
                        signal: signalIndex
                    });
                }
            }
        };
    }

    /**
     * Invokes all callbacks for the given signalname. Also works for property notify callbacks.
     */
    function invokeSignalCallbacks(signalName, signalArgs)
    {
        var connections = object.__objectSignals__[signalName];
        if (connections) {
            connections.forEach(function(callback) {
                callback.apply(callback, signalArgs);
            });
        }
    }

    this.propertyUpdate = function(signals, propertyMap)
    {
        // update property cache
        for (var propertyIndex in propertyMap) {
            var propertyValue = propertyMap[propertyIndex];
            object.__propertyCache__[propertyIndex] = propertyValue;
        }

        for (var signalName in signals) {
            // Invoke all callbacks, as signalEmitted() does not. This ensures the
            // property cache is updated before the callbacks are invoked.
            invokeSignalCallbacks(signalName, signals[signalName]);
        }
    }

    this.signalEmitted = function(signalName, signalArgs)
    {
        invokeSignalCallbacks(signalName, signalArgs);
    }

    function addMethod(methodData)
    {
        var methodName = methodData[0];
        var methodIdx = methodData[1];
        object[methodName] = function() {
            var args = [];
            var callback;
            for (var i = 0; i < arguments.length; ++i) {
                if (typeof arguments[i] === "function")
                    callback = arguments[i];
                else
                    args.push(arguments[i]);
            }

            webChannel.exec({
                "type": QWebChannelMessageTypes.invokeMethod,
                "object": object.__id__,
                "method": methodIdx,
                "args": args
            }, function(response) {
                if (response !== undefined) {
                    var result = object.unwrapQObject(response);
                    if (callback) {
                        (callback)(result);
                    }
                }
            });
        };
    }

    function bindGetterSetter(propertyInfo)
    {
        var propertyIndex = propertyInfo[0];
        var propertyName = propertyInfo[1];
        var notifySignalData = propertyInfo[2];
        // initialize property cache with current value
        // NOTE: if this is an object, it is not directly unwrapped as it might
        // reference other QObject that we do not know yet
        object.__propertyCache__[propertyIndex] = propertyInfo[3];

        if (notifySignalData) {
            if (notifySignalData[0] === 1) {
                // signal name is optimized away, reconstruct the actual name
                notifySignalData[0] = propertyName + "Changed";
            }
            addSignal(notifySignalData, true);
        }

        Object.defineProperty(object, propertyName, {
            configurable: true,
            get: function () {
                var propertyValue = object.__propertyCache__[propertyIndex];
                if (propertyValue === undefined) {
                    // This shouldn't happen
                    console.warn("Undefined value in property cache for property \"" + propertyName + "\" in object " + object.__id__);
                }

                return propertyValue;
            },
            set: function(value) {
                if (value === undefined) {
                    console.warn("Property setter for " + propertyName + " called with undefined value!");
                    return;
                }
                object.__propertyCache__[propertyIndex] = value;
                webChannel.exec({
                    "type": QWebChannelMessageTypes.setProperty,
                    "object": object.__id__,
                    "property": propertyIndex,
                    "value": value
                });
            }
        });

    }

    // ----------------------------------------------------------------------

    data.methods.forEach(addMethod);

    data.properties.forEach(bindGetterSetter);

    data.signals.forEach(function(signal) { addSignal(signal, false); });

    for (var name in data.enums) {
        object[name] = data.enums[name];
    }
}

//required for use with nodejs
if (typeof module === 'object') {
    module.exports = {
        QWebChannel: QWebChannel
    };
}

3.涉及相关Qt工程文件

main.cpp 文件：

#include <QApplication>
#include "TMainWindow.h"

int main(int argc, char** argv)
{
    QApplication app(argc, argv);

    TMainWindow mainWindow;
    mainWindow.show();
    return app.exec();
}

TMainWindow.h 文件：

#ifndef TMAINWINDOW_H
#define TMAINWINDOW_H

#include <QDialog>

QT_BEGIN_NAMESPACE
class QPlainTextEdit;
class QLineEdit;
class QPushButton;
class QWebEngineView;
QT_END_NAMESPACE

class TMainWindow : public QDialog
{
    Q_OBJECT

public:
    TMainWindow(QDialog *parent = 0);
    ~TMainWindow();

    void OnReceiveMessageFromJS(QString strParameter);
    
signals:
    void SigSendMessageToJS(QString strParameter);

private:
    void OnSendMessageByInteractObj();
    void OnSendMessageByJavaScript();

    QPlainTextEdit *mpQtContentTextEdit;
    QLineEdit      *mpQtSendLineEdit;
    QPushButton    *mpQtSendBtnByInteractObj;
    QPushButton    *mpQtSendBtnByJavaScript;
    QWebEngineView *mpJSWebView;
};

#endif //TMAINWINDOW_H 

TMainWindow.cpp 文件：

#include "TMainWindow.h"
#include "TInteractObject.h"

#include <QPlainTextEdit>
#include <QLineEdit>
#include <QPushButton>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QGroupBox>
#include <QWebChannel>
#include <QWebEngineView>
#include <QFileInfo>

TMainWindow::TMainWindow(QDialog *parent)
    : QDialog(parent)
{
    //---Qt widget and layout---
    mpQtContentTextEdit      = new QPlainTextEdit(this);
    mpQtContentTextEdit->setMidLineWidth(400);
    mpQtContentTextEdit->setReadOnly(true);

    mpQtSendLineEdit         = new QLineEdit(this);
    mpQtSendBtnByInteractObj = new QPushButton("Send", this);
    mpQtSendBtnByInteractObj->setToolTip(tr("Send message by Interact object style"));

    mpQtSendBtnByJavaScript  = new QPushButton("Send2", this);
    mpQtSendBtnByJavaScript->setToolTip(tr("Send message by runJavaScript style"));

    QHBoxLayout *pQtSendHLayout = new QHBoxLayout;
    pQtSendHLayout->setMargin(0);
    pQtSendHLayout->setSpacing(0);
    pQtSendHLayout->addWidget(mpQtSendLineEdit);
    pQtSendHLayout->addSpacing(5);
    pQtSendHLayout->addWidget(mpQtSendBtnByInteractObj);
    pQtSendHLayout->addSpacing(5);
    pQtSendHLayout->addWidget(mpQtSendBtnByJavaScript);

    QVBoxLayout *pQtTotalVLayout = new QVBoxLayout;
    pQtTotalVLayout->setMargin(5);
    pQtTotalVLayout->setSpacing(0);
    pQtTotalVLayout->addWidget(mpQtContentTextEdit);
    pQtTotalVLayout->addSpacing(5);
    pQtTotalVLayout->addLayout(pQtSendHLayout);

    QGroupBox *pQtGroup = new QGroupBox("Qt View", this);
    pQtGroup->setLayout(pQtTotalVLayout);

    //---Web widget and layout---
    mpJSWebView = new QWebEngineView(this);

    QWebChannel *pWebChannel   = new QWebChannel(mpJSWebView->page());
    TInteractObj *pInteractObj = new TInteractObj(this);
    pWebChannel->registerObject(QStringLiteral("interactObj"), pInteractObj);

    mpJSWebView->page()->setWebChannel(pWebChannel);
    mpJSWebView->page()->load(QUrl::fromLocalFile(QFileInfo("./JSTest.html").absoluteFilePath()));
    mpJSWebView->show();

    QVBoxLayout *pJSTotalVLayout = new QVBoxLayout();
    pJSTotalVLayout->setMargin(0);
    pJSTotalVLayout->setSpacing(0);
    pJSTotalVLayout->addWidget(mpJSWebView);

    QGroupBox *pWebGroup = new QGroupBox("Web View", this);
    pWebGroup->setLayout(pJSTotalVLayout);

    //---TMainWindow total layout---
    QHBoxLayout *mainLayout = new QHBoxLayout;
    mainLayout->setMargin(5);
    mainLayout->setSpacing(0);
    mainLayout->addWidget(pQtGroup);
    mainLayout->addSpacing(5);
    mainLayout->addWidget(pWebGroup);
    setLayout(mainLayout);
    this->setMinimumSize(800, 600);

    connect(mpQtSendBtnByInteractObj, &QPushButton::clicked,                this,         &TMainWindow::OnSendMessageByInteractObj);
    connect(mpQtSendBtnByJavaScript,  &QPushButton::clicked,                this,         &TMainWindow::OnSendMessageByJavaScript);
    connect(pInteractObj,             &TInteractObj::SigReceivedMessFromJS, this,         &TMainWindow::OnReceiveMessageFromJS);
    connect(this,                     &TMainWindow::SigSendMessageToJS,     pInteractObj, &TInteractObj::SigSendMessageToJS);
}

TMainWindow::~TMainWindow()
{
}

void TMainWindow::OnReceiveMessageFromJS(QString strParameter)
{
    if (strParameter.isEmpty())
    {
        return;
    }

    mpQtContentTextEdit->appendPlainText(strParameter);
}

void TMainWindow::OnSendMessageByInteractObj()
{
    QString strMessage = mpQtSendLineEdit->text().trimmed();
    if (strMessage.isEmpty())
    {
        return;
    }

    emit SigSendMessageToJS(strMessage);
}

void TMainWindow::OnSendMessageByJavaScript()
{
    QString strMessage = mpQtSendLineEdit->text().trimmed();
    if (strMessage.isEmpty())
    {
        return;
    }

    strMessage = QString("Received string from Qt: %1").arg(strMessage);
    mpJSWebView->page()->runJavaScript(QString("output('%1');").arg(strMessage));
}

说明：

TInteractObject.h 文件：

#ifndef TINTERACT_OBJECT_H
#define TINTERACT_OBJECT_H

#include <QObject>

class TInteractObj : public QObject
{
    Q_OBJECT

public:
    TInteractObj(QObject *parent);
    ~TInteractObj();

    Q_INVOKABLE void JSSendMessage(QString strParameter);       //Called by JS: Send message to Qt

signals:
    void SigReceivedMessFromJS(QString strParameter);          //Receive message from Web

    void SigSendMessageToJS(QString strParameter);             //Send message to Web
};


#endif //TINTERACT_OBJECT_H 

说明：

TInteractObject.cpp 文件：

#include "TInteractObject.h"

TInteractObj::TInteractObj(QObject *parent)
    :QObject(parent)
{
}

TInteractObj::~TInteractObj()
{
}

void TInteractObj::JSSendMessage(QString strParameter)
{
    emit SigReceivedMessFromJS(strParameter);
}

4.页面端模拟文件JSTest.html

<!DOCTYPE html>  
<html>  
    <head>  
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
        <script type="text/javascript" src="qrc:///qtwebchannel/qwebchannel.js"></script>  
        <script type="text/javascript">  
        //---Web show receive message---
        function output(message)  
        {  
            var output = document.getElementById("output");  
            output.innerHTML = output.innerHTML + message + "\n";  
        }  
        
        //Web initial loading 
         window.onload = function() {  
            output("");  
            new QWebChannel(qt.webChannelTransport, function(channel) { 
            
                //Get Qt interact object  
                var interactObj = channel.objects.interactObj; 
                
                //Web send message to Qt 
                document.getElementById("send").onclick = function() {  
                    var input = document.getElementById("input");  
                    if (!input.value) {  
                        return;  
                    }  
                    
                    //Web use the interface of Qt 
                    interactObj.JSSendMessage(input.value);  
                    input.value = "";                      
                }  
                
                //Web connect the Qt signal, then Qt can call "output" function
                interactObj.SigSendMessageToJS.connect(function(str) {  
                    output("Received string from Qt: " + str);  
                });    
            });  
            }  
  
        </script>  
        <style type="text/css">  
            html {  
                height: 100%;  
                width: 100%;  
            }  
            #input {  
                width: 650px;  
                margin: 0 10px 0 0;  
            }  
            #send {  
                width: 90px;  
                margin: 0;  
            }  
            #output {  
                width: 770px;  
                height: 550px;  
            }  
        </style>  
    </head>  
    <body>  
        <textarea id="output" readonly="readonly"></textarea><br />  
        <input id="input" />  
        <input type="submit" id="send" value="Send" onclick="javascript:click();" />  
    </body>  
</html>  

说明：

5.运行效果

Qt界面Send按钮通过QtWebChannel绑定对象，向Web页面端发送消息("Hello JavaScript")；
Qt界面Send2按钮通过runJavaScript调用页面端公共接口，向Web页面端发送消息("Hello JavaScript")；
Web页面端Send按钮通过关联Qt界面公共接口，向Qt端发送消息("Hello Qt")；