从javascript返回值到pyqt5 [英] Return value from javascript to pyqt5
问题描述
我正在尝试从PyQt5应用程序内部加载和查询JS地图窗口小部件。我可以使用这个方法：
I'm trying to load and query a JS map widget from inside a PyQt5 application. I'm able to use the method:
PyQt5.QtWebEngineWidgets.QWebEngineView（）。page（）。runJavaScript（）
从 QWebEngineView（）中加载的网页执行JS功能但是我遇到了麻烦了解如何将一个由JS函数返回的值存储回python。
to execute JS function from the webpage loaded in a QWebEngineView() but I'm having troubles in understanding how to store back to python a value which is returned by a JS function.
这里有一个完整的例子：
A complete example is available here:
以下PyQt5代码使用 leaflet.js 地图窗口小部件加载html页面（ pyqtwebtest.html ）在PyQt4主窗口中添加一个按钮来执行JS代码，目的是将返回的值存储在python变量中...
The following PyQt5 code load an html page (pyqtwebtest.html) with a leaflet.js map widget inside a PyQt4 mainwindow and add a button to execute a JS code with the aim to store the returned value inside a python variable ...
#!/usr/local/bin/python36
import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
from PyQt5.QtWebEngineWidgets import *
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.form_widget = FormWidget(self)
_widget = QWidget()
_layout = QVBoxLayout(_widget)
_layout.addWidget(self.form_widget)
self.setCentralWidget(_widget)
class FormWidget(QWidget):
def __init__(self, parent):
super(FormWidget, self).__init__(parent)
self.__controls()
self.__layout()
def __controls(self):
self.browser = QWebEngineView()
self.browser.load(QUrl('file:///Users/epi/pyqtwebtest.html'))
def __layout(self):
self.vbox = QVBoxLayout()
self.hBox = QVBoxLayout()
self.getboundsbutton = QPushButton()
self.hBox.addWidget(self.browser)
self.hBox.addWidget(self.getboundsbutton)
self.vbox.addLayout(self.hBox)
self.setLayout(self.vbox)
self.getboundsbutton.clicked.connect(self.getBounds)
def getBounds(self):
self.bounds = self.browser.page().runJavaScript("[map.getBounds().getSouthWest().lat, map.getBounds().getSouthWest().lng, map.getBounds().getNorthEast().lat, map.getBounds().getNorthEast().lng]")
print(self.bounds)
# this is where I get stuck .. the result is None
# the same js code in the html file prints the bounds values
# that I want to store on the python side of the app
def main():
app = QApplication(sys.argv)
win = MainWindow()
win.show()
app.exec_()
if __name__ == '__main__':
sys.exit(main())
加载以下html页面：
which load the following html page:
<!DOCTYPE html>
<html>
<head>
<title>PyQtLeaflet</title>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<link rel="shortcut icon" type="image/x-icon" href="docs/images/favicon.ico" />
<link rel="stylesheet" href="https://unpkg.com/leaflet@1.0.2/dist/leaflet.css" />
<script src="https://unpkg.com/leaflet@1.0.2/dist/leaflet.js"></script>
<style>
#map {
width: 600px;
height: 400px;
}
</style>
</head>
<body>
<div id='map'></div>
<script>
var mbAttr = 'Map data © <a href="http://openstreetmap.org">OpenStreetMap</a> contributors, ' +
'<a href="http://creativecommons.org/licenses/by-sa/2.0/">CC-BY-SA</a>, ' +
'Imagery © <a href="http://mapbox.com">Mapbox</a>',
mbUrl = 'https://api.tiles.mapbox.com/v4/{id}/{z}/{x}/{y}.png?access_token=pk.eyJ1IjoibWFwYm94IiwiYSI6ImNpandmbXliNDBjZWd2M2x6bDk3c2ZtOTkifQ._QA7i5Mpkd_m30IGElHziw';
var grayscale = L.tileLayer(mbUrl, {id: 'mapbox.light', attribution: mbAttr}),
streets = L.tileLayer(mbUrl, {id: 'mapbox.streets', attribution: mbAttr});
var map = L.map('map', {
center: [10, 10],
zoom: 10,
layers: [grayscale]
});
var baseLayers = {
"Grayscale": grayscale,
"Streets": streets
};
L.control.layers(baseLayers).addTo(map);
// this is the "bounds" variable which I am trying to get from pyqt
bounds = [map.getBounds().getSouthWest().lat, map.getBounds().getSouthWest().lng, map.getBounds().getNorthEast().lat, map.getBounds().getNorthEast().lng]
console.log(bounds)
</script>
</body>
</html>
我知道这个问题可能被认为是重复但是我很难找到最近版本的pyqt5完全相同的方法（> = 5.7）
I understand that this question may be considered a duplicate but I had difficulties in finding the exact same methods for a recent version of pyqt5 (>=5.7)
推荐答案
runJavaScript 异步工作，因此它永远不会返回一个值 - 而是将一个回调（即Python函数）传递给它，并使用javascript值调用它。对于您的示例，您只需传递 print 作为第二个参数。
runJavaScript in QtWebEngine works asynchronously, so it never returns a value - instead, you pass a callback (i.e. a Python function) to it which gets called with the javascript value. For your example, you could simply pass print as second argument.
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