问题描述
===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()