如何等待通过QNetworkAccessManager完成两次异步下载？

如何解决如何等待通过QNetworkAccessManager完成两次异步下载？

===摘要============================================

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qnetworkrequests。完成后，每个请求都将图像内容写入文件。

问题是，两个请求彼此都不知道，因此，无法验证另一个请求是否已完成。

您能否告诉我我如何等待两个请求完成？

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_()

解决方法

您必须创建一个跟踪下载的类：

from dataclasses import dataclass
import sys

from PyQt5.QtCore import pyqtSignal,QObject,QUrl,QFile,QIODevice
from PyQt5.QtNetwork import QNetworkAccessManager,QNetworkRequest,QNetworkReply
from PyQt5.QtWidgets import QApplication,QWidget


@dataclass
class DownloadRequest:
    url: QUrl
    filename: str


class 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()