SEGV_MAPERR 对于 PyQt5 对象

Question

为什么下面的演示代码会产生一个SEGV_MAPERR？如何解决它？

提示：一旦删除了“#ref1”注释的行，就不会产生错误。这在从问题中抽象出来的生产代码中不容易完成。

from PyQt5 import QtCore, QtGui, QtWidgets, QtWebChannel

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.webView = QtWebEngineWidgets.QWebEngineView(self.centralwidget)
        self.webView.setHtml("")
        self.gridLayout.addWidget(self.webView, 0, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)
        page = self.webView.page() # REF1
        for i in range(2):
            self.init_page()

    def init_page(self):
        class EditObject(QtCore.QObject):
            @QtCore.pyqtSlot(str)
            def edit(self, s):
                print("test")
        editObject = EditObject(self.webView.page())
        poChannel = self.webView.page().webChannel()
        print(1)
        if poChannel is None:
            poChannel = QtWebChannel.QWebChannel()
            self.webView.page().setWebChannel(poChannel)
        print(2)
        objects = poChannel.registeredObjects()
        print(objects)
        poChannel.registerObject("editObject", editObject)
        self.webView.setHtml("")

from PyQt5 import QtWebEngineWidgets

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    MainWindow = QtWidgets.QMainWindow()
    ui = Ui_MainWindow()
    ui.setupUi(MainWindow)
    MainWindow.show()
    sys.exit(app.exec_())

这类似于Issues with PyQt5==5.10 on Ubuntu 18, but with example code. For the example code, https://gist.github.com/gioditalia/03c9fd5d793aeccbe065fea45d842431改编。

Answer 1

问题是poChannel是一个局部变量，执行完init_page就会被删除，所以在第二次迭代中poChannel引用会指向一个不正确的内存地址。所以解决方案是将它的周期扩展到视图的周期，所以我们利用 Qt 属性并将其作为父级传递给 self.webView.

poChannel = QtWebChannel.QWebChannel(self.webView)

虽然 PyQt 在 the docs 和生成的文件中指出：# WARNING! All changes made in this file will be lost!，但修改 .ui 生成的 class 并不方便，而是您必须创建另一个 class 从适当的小部件继承并使用 Qt Designer 提供的界面。

from PyQt5 import QtCore, QtGui, QtWidgets, QtWebEngineWidgets, QtWebChannel

class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.gridLayout = QtWidgets.QGridLayout(self.centralwidget)
        self.webView = QtWebEngineWidgets.QWebEngineView(self.centralwidget)
        self.gridLayout.addWidget(self.webView, 0, 0, 1, 1)
        MainWindow.setCentralWidget(self.centralwidget)

class EditObject(QtCore.QObject):
    @QtCore.pyqtSlot(str)
    def edit(self, s):
        print("test")

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.setupUi(self)
        for i in range(2):
            self.init_page()

    def init_page(self):
        editObject = EditObject(self.webView.page())
        poChannel = self.webView.page().webChannel()
        if poChannel is None:
            poChannel = QtWebChannel.QWebChannel(self)
            self.webView.page().setWebChannel(poChannel)
        objects = poChannel.registeredObjects()
        poChannel.registerObject("editObject", editObject)

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

SEGV_MAPERR 对于 PyQt5 对象

SEGV_MAPERR for PyQt5 object

python

pyqt

segmentation-fault

pyqt5

qobject