后台工作人员填充 QListView 缩略图

Question

我有一个显示项目名称列表的简单 QListview。我想在下载后显示每个项目的缩略图。我如何执行以下操作，因为我不熟悉使用后台工作人员之类的东西并且我不确定如何实现这一点。

这解释了我认为最好的方法......

• 使用覆盖 initStyleOption() 函数的自定义 QStyledItemDelegate。

• 检测缺少图标并发出异步请求以加载它。

• 同时，显示默认的空图标，以便用户看到占位符

• 当下载图标的异步请求完成时，它会通知我的小部件更新项目图标。

• 当我创建所有 QStandardModelItems 时，我给他们一个自定义数据（自定义角色），其中包含每个项目的缩略图路径

  import os
  import sys
  from PySide2 import QtCore, QtGui, QtWidgets
  
  try:
      # python 2
      from urllib import urlretrieve
      from urllib2 import urlopen
  except Exception as e:
      # python 3
      from urllib.request import urlretrieve, urlopen
  
  import time
  from urllib.parse import urlparse
  
  def getThumbnail(url, output):
      if os.path.exists(output):
          return output
      # # download 1
      # # urlretrieve(url, output)
      # # return os.path.abspath(output)
  
      # download 2
      response = urlopen(url, timeout=5000)
      f = open(output, "wb")
      try:
          f.write(response.read())
      finally:
          f.close()
      return output
  
  class ExampleDialog(QtWidgets.QDialog):
  
      def __init__(self):
          super(ExampleDialog, self).__init__()
  
          self.itemModel = QtGui.QStandardItemModel()
  
          self.uiListView = QtWidgets.QListView()
          # self.uiListView.setViewMode(QtWidgets.QListView.IconMode)
          self.uiListView.setIconSize(QtCore.QSize(80, 60))  #set icon size
          self.uiListView.setGridSize(QtCore.QSize(90, 70)) #set icon grid display
          self.uiListView.setModel(self.itemModel)
  
          self.mainLayout = QtWidgets.QVBoxLayout(self)
          self.mainLayout.addWidget(self.uiListView)
  
          self.populateImages()
  
  
      def populateImages(self):
          root = os.path.join(os.getenv('APPDATA'), 'MyApp\\cache')
          if not os.path.exists(root):
              os.makedirs(root)
  
          print('IMAGES:', root)
  
          for x in range(20):
              url = 'https://picsum.photos/id/{}/80/60.jpg'.format(x)
  
              p = urlparse(url).path
              ext = os.path.splitext(p)[-1]
              output = os.path.join(root, '{}{}'.format(x, ext))
  
              # get thumbnail
              getThumbnail(url, output)
  
              # Item
              item = QtGui.QStandardItem('{}'.format(x))
              item.setData(QtGui.QPixmap(output), QtCore.Qt.DecorationRole)
              item.setData(output, QtCore.Qt.UserRole)
              self.itemModel.appendRow(item)
  
  if __name__ == '__main__':
      app = QtWidgets.QApplication(sys.argv)
      window =  ExampleDialog()
      window.show()
      window.raise_()
      sys.exit(app.exec_())
  

Answer 1

您可以使用 QNetworkAccessManager 进行异步下载，而不是使用后台工作程序。

from dataclasses import dataclass
from functools import cached_property
import sys

from PySide2 import QtCore, QtGui, QtWidgets, QtNetwork


@dataclass
class IconDownloader(QtCore.QObject):
    url: QtCore.QUrl
    index: QtCore.QPersistentModelIndex
    _parent: QtCore.QObject = None

    def __post_init__(self):
        super().__init__()
        self.setParent(self._parent)

    @cached_property
    def network_manager(self):
        manager = QtNetwork.QNetworkAccessManager()
        manager.finished.connect(self._handle_finished)
        return manager

    def start(self):
        if self.index.isValid():
            request = QtNetwork.QNetworkRequest(self.url)
            request.setAttribute(
                QtNetwork.QNetworkRequest.FollowRedirectsAttribute, True
            )
            self.network_manager.get(request)

    def _handle_finished(self, reply):
        if reply.error() == QtNetwork.QNetworkReply.NoError:
            pixmap = QtGui.QPixmap()
            ok = pixmap.loadFromData(reply.readAll())
            if ok and self.index.isValid():
                model = self.index.model()
                model.setData(
                    QtCore.QModelIndex(self.index), pixmap, QtCore.Qt.DecorationRole
                )
        else:
            print(reply.error(), reply.errorString())
        reply.deleteLater()
        self.deleteLater()


class ExampleDialog(QtWidgets.QDialog):
    def __init__(self):
        super(ExampleDialog, self).__init__()

        self.itemModel = QtGui.QStandardItemModel()

        self.uiListView = QtWidgets.QListView()
        # self.uiListView.setViewMode(QtWidgets.QListView.IconMode)
        self.uiListView.setIconSize(QtCore.QSize(80, 60))  # set icon size
        self.uiListView.setGridSize(QtCore.QSize(90, 70))  # set icon grid display
        self.uiListView.setModel(self.itemModel)

        self.mainLayout = QtWidgets.QVBoxLayout(self)
        self.mainLayout.addWidget(self.uiListView)

        self.populateImages()

    def populateImages(self):
        for x in range(20):
            url = f"https://picsum.photos/id/{x}/80/60.jpg"
            item = QtGui.QStandardItem(f"x")
            self.itemModel.appendRow(item)
            downloader = IconDownloader(
                QtCore.QUrl(url),
                QtCore.QPersistentModelIndex(self.itemModel.indexFromItem(item)),
                self,
            )
            downloader.start()


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    window = ExampleDialog()
    window.show()
    window.raise_()
    sys.exit(app.exec_())