使用QtNetwork和PyQt5检查互联网连接情况

Question

我试图用QtNetwork来检查网络的连通性，但却找不出正确的方法。这是我正在编写的代码，似乎既没有调用finished信号，也没有调用error信号。我在这里错过了什么？

import sys
from PyQt5 import QtCore, QtNetwork, QtWidgets


class CheckConnectivity:
    def __init__(self):
        url = QtCore.QUrl("https://www.google.com/")
        req = QtNetwork.QNetworkRequest(url)
        net_manager = QtNetwork.QNetworkAccessManager()
        self.res = net_manager.get(req)
        self.res.finished.connect(self.processRes)
        self.res.error.connect(self.processErr)
        self.msg = QtWidgets.QMessageBox()

    def processRes(self):
        if self.res.bytesAvailable():
            self.msg.information(self, "Info", "You are connected to the Internet.")
        else:
            self.msg.critical(self, "Info", "You are not connected to the Internet.")
        self.msg.show()
        self.res.close()

    def processErr(self, *args):
        print(*args)


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    ic = CheckConnectivity()
    sys.exit(app.exec_())

Answer 1

问题是因为net_manager被删除了，请记住，变量只存在于创建变量的上下文中，在您的示例中，net_manager是一个局部变量，在__init__方法结束时将被删除。

class CheckConnectivity(QtCore.QObject):
    def __init__(self, *args, **kwargs):
        QtCore.QObject.__init__(self, *args, **kwargs)
        url = QtCore.QUrl("https://www.google.com/")
        req = QtNetwork.QNetworkRequest(url)
        self.net_manager = QtNetwork.QNetworkAccessManager()
        self.res = self.net_manager.get(req)
        self.res.finished.connect(self.processRes)
        self.res.error.connect(self.processErr)
        self.msg = QtWidgets.QMessageBox()

    @QtCore.pyqtSlot()
    def processRes(self):
        if self.res.bytesAvailable():
            self.msg.information(None, "Info", "You are connected to the Internet.")
        self.res.deleteLater()

    @QtCore.pyqtSlot(QtNetwork.QNetworkReply.NetworkError)
    def processErr(self, code):
        self.msg.critical(None, "Info", "You are not connected to the Internet.")
        print(code)

使用pyqtSlot()装饰器是明智的，因为它的使用可以帮助应用程序更快一些，消耗更少的内存，但是为此类必须从QObject继承。