PyQt5中使用QWebChannel和内嵌网页进行js交互
2018-11-09 本文已影响418人
yuchanns
项目上需要将网页内嵌到客户端可执行程序上使用。以前同事通常是使用C#的WinFrom解决，不过这次却因为兼容性问题（WinForm内核是IE7，不懂C#不知道怎么修改），不支持大部分BootStrap样式。于是我就用PyQt5的QWebEngineView写了个简单客户端代替。样式支持了，但是却遇到一个问题，网页有打印需求，调用js的window.print()而QWebEngineView却无法接收到打印请求作出反应。
经过查询资料和网友的提醒之后，我决定用QWebChannel来解决这个问题。
注：由于在查阅过程中没有及时保存参考来源，所以这里就不贴出参考的文章链接，请见谅
>>>原文地址
以下放出demo：
python端代码
#! /usr/bin/env
# -*- coding: utf-8 -*-
# webview.py
from PyQt5.QtWidgets import QApplication
from PyQt5.QtCore import QObject, pyqtSlot, QUrl
from PyQt5.QtWebChannel import QWebChannel
from PyQt5.QtWebEngineWidgets import QWebEngineView
import sys
class Print(QObject):
# pyqtSlot，中文网络上大多称其为槽。作用是接收网页发起的信号
@pyqtSlot(str, result=str)
def print(self, content):
print(content) # 对接收到的内容进行处理，比如调用打印机进行打印等等。此处略去，只在bash中显示接收到的消息
return content
if __name__ == '__main__':
app = QApplication(sys.argv)
browser = QWebEngineView() # 新增一个浏览器引擎
browser.setWindowTitle('QWebChannel交互Demo')
browser.resize(900, 600)
channel = QWebChannel() # 增加一个通信中需要用到的频道
printer = Print() # 通信过程中需要使用到的功能类
channel.registerObject('printer', printer) # 将功能类注册到频道中，注册名可以任意，但将在网页中作为标识
browser.page().setWebChannel(channel) # 在浏览器中设置该频道
url_string = "file:///G:/python/webview/index.html" # 内置的网页地址，此处我采用的是本地的。远程同样可以使用。
browser.load(QUrl(url_string))
browser.show()
sys.exit(app.exec_())
网页端代码
<!-- index.html -->
<!DOCTYPE html>
<html>
<title>QWebChannel交互Demo</title>
<body>
<button onclick="sendMes()">发送消息</button>
<p id="mes"></p>
<!-- 引入qwebchannel.js，才能与QWebEngineView进行交互 -->
<script type="text/javascript" src="qwebchannel.js"></script>
<script>
window.onload = function() {
new QWebChannel(qt.webChannelTransport, function (channel) {
window.printer= channel.objects.printer; // 此处channel.objects.printer中的printer就是上文提到的功能类注册的标识名
});
};
function sendMes() { // 调用python端的功能类的方法执行操作
printer.print('你收到一条网页发送的消息！')
}
</script>
</body>
</html>
QWebChannel交互Demo
以上就是解决方案。事实上交互一词还包含了从QWebEngineView向网页发送信号的部分，因为暂时没用到，所以demo上没有写出。后面我再补上。
附：qwebchannel.js库内容
/****************************************************************************
**
** Copyright (C) 2016 The Qt Company Ltd.
** Contact: http://www.qt.io/licensing/
**
** This file is part of the examples of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:BSD$
** You may use this file under the terms of the BSD license as follows:
**
** "Redistribution and use in source and binary forms, with or without
** modification, are permitted provided that the following conditions are
** met:
** * Redistributions of source code must retain the above copyright
** notice, this list of conditions and the following disclaimer.
** * Redistributions in binary form must reproduce the above copyright
** notice, this list of conditions and the following disclaimer in
** the documentation and/or other materials provided with the
** distribution.
** * Neither the name of The Qt Company Ltd nor the names of its
** contributors may be used to endorse or promote products derived
** from this software without specific prior written permission.
**
**
** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
**
** $QT_END_LICENSE$
**
****************************************************************************/
"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
};
}
