如何通过 QNetworkAccessManager 等待两个异步下载完成？

Question

===总结=============================================

我使用 QNetworkAccessManager 和 QNetworkRequests 同时下载两个图像。我如何确定两次下载已完成？

===详细说明=================================

我有两个图像的 URL，我想异步下载它们。为此，我初始化 QNetworkAccessManager 并使用两个 QNetworkRequest。完成后，每个请求都会将图像的内容写入文件中。

问题是两个请求彼此一无所知，因此无法验证另一个请求是否已完成。

您能告诉我如何等待这两个请求完成吗？

这是完整的代码：

import sys

from PyQt5.QtCore import QUrl, QFile, QIODevice

from PyQt5.QtNetwork import QNetworkAccessManager, QNetworkRequest

from PyQt5.QtWidgets import QApplication, QWidget

class MainWindow(QWidget):

    def __init__(self):

        super(MainWindow, self).__init__()

        img_url1 = "https://somesite.com/image1.jpg"

        img_url2 = "https://somesite.com/image2.jpg"

        self.downloader = QNetworkAccessManager()

        self.requests = []

        self.temp_files = []

        for index, mediafile_url in enumerate([img_url1, img_url2]):

            self.requests.append(self.downloader.get(QNetworkRequest(QUrl(mediafile_url))))

            request = self.requests[index]

            self.temp_files.append(QFile(f'{mediafile_url.split("/")[-1]}'))

            temp_file = self.temp_files[index]

            request.finished.connect(lambda *args, r=request, tf=temp_file: self.download_image(r, tf))

        self.show()

    @staticmethod

    def download_image(request, temp_file):

        image_data = request.readAll()

        temp_file.open(QIODevice.WriteOnly)

        temp_file.write(image_data)

        temp_file.close()

app = QApplication(sys.argv)

window = MainWindow()

app.exec_()

Answer 1

您必须创建一个跟踪下载的类：from dataclasses import dataclassimport sysfrom PyQt5.QtCore import pyqtSignal, QObject, QUrl, QFile, QIODevicefrom PyQt5.QtNetwork import QNetworkAccessManager, QNetworkRequest, QNetworkReplyfrom PyQt5.QtWidgets import QApplication, QWidget@dataclassclass DownloadRequest:    url: QUrl    filename: strclass DownloadManager(QObject):    finished = pyqtSignal()    def __init__(self, parent=None):        super().__init__(parent)        self._manager = QNetworkAccessManager()        self._pending_downloads = 0        self.manager.finished.connect(self.handle_finished)    @property    def manager(self):        return self._manager    @property    def pending_downloads(self):        return self._pending_downloads    def download(self, requests):        for request in requests:            qrequest = QNetworkRequest(request.url)            qrequest.setAttribute(QNetworkRequest.User, request.filename)            self.manager.get(qrequest)            self._pending_downloads += 1    def handle_finished(self, reply):        self._pending_downloads -= 1        if reply.error() != QNetworkReply.NoError:            print(f"code: {reply.error()} message: {reply.errorString()}")        else:            print("successful")            filename = reply.attribute(QNetworkRequest.User)            file = QFile(filename)            if file.open(QIODevice.WriteOnly):                file.write(reply.readAll())        print(f"pending downloads {self.pending_downloads}")        if self.pending_downloads == 0:            self.finished.emit()class MainWindow(QWidget):    def __init__(self, parent=None):        super().__init__(parent)        self._manager = DownloadManager()        self._manager.finished.connect(self.handle_finished)        img_url1 = "https://docs.python.org/3/_static/py.png"        img_url2 = "https://somesite.com/image2.jpg"        request1 = DownloadRequest(QUrl(img_url1), img_url1.split("/")[-1])        request2 = DownloadRequest(QUrl(img_url2), img_url2.split("/")[-1])        self._manager.download([request1, request2])    def handle_finished(self):        print("finished")def main():    app = QApplication(sys.argv)    window = MainWindow()    window.show()    app.exec_()if __name__ == "__main__":    main()