我一直在为PySide2
制作C++
示例代码
我一遍又一遍地复习fetchMore example
这种转换的错误点在哪里
最大的问题是数据方法
角色总是SizeHintRole
为什么?
这是代码
# -*- coding: utf-8 -*-
import sys, os, PySide2
from PySide2 import QtCore, QtWidgets, QtGui
dirname = os.path.dirname(PySide2.__file__)
plugin_path = os.path.join(dirname, 'plugins', 'platforms')
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = plugin_path
class Window(QtWidgets.QWidget):
def __init__(self, parent=None):
super(Window, self).__init__(parent)
self.model = FileListModel()
#6.0
# self.model.setDirPath(QtCore.QLibraryInfo.path(QtCore.QLibraryInfo.PrefixPath))
self.model.setDirPath(QtCore.QLibraryInfo.location(QtCore.QLibraryInfo.PrefixPath))
self.label = QtWidgets.QLabel("&Directory:")
self.lineEdit = QtWidgets.QLineEdit()
self.label.setBuddy(self.lineEdit)
self.view = QtWidgets.QListView()
self.view.setModel(self.model)
self.logViewer = QtWidgets.QTextBrowser(self)
self.logViewer.setSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
self.lineEdit.textChanged["QString"].connect(self.model.setDirPath)
self.lineEdit.textChanged["QString"].connect(self.logViewer.clear)
self.model.numberPopulated[int].connect(self.updateLog)
layout = QtWidgets.QGridLayout()
layout.addWidget(self.label, 0, 0)
layout.addWidget(self.lineEdit, 0, 1)
layout.addWidget(self.view, 1, 0, 1, 2)
layout.addWidget(self.logViewer, 2, 0, 1, 2)
self.setLayout(layout)
self.setWindowTitle("Fetch More Example")
def updateLog(self, number):
self.logViewer.append("{0} items added.".format(number))
class FileListModel(QtCore.QAbstractListModel):
numberPopulated = QtCore.Signal(int)
def __init__(self, parent=None):
super(FileListModel, self).__init__(parent)
self.fileCount = 0
self.fileList = []
def rowCount(self, parent=QtCore.QModelIndex()):
return 0 if parent.isValid() else self.fileCount
def data(self, index, role=QtCore.Qt.DisplayRole):
if not index.isValid():
return 0
if (index.row() >= len(self.fileList) or index.row() < 0):
return 0
#Why is the role only SizeHintRole?
if role == QtCore.Qt.DisplayRole:
return self.fileList[index.row()]
elif role == QtCore.Qt.BackgroundRole:
batch = (index.row() / 100) % 2
if batch == 0:
return QtWidgets.QApplication.palette().base()
else:
return QtWidgets.QApplication.palette().alternateBase()
return 0
def canFetchMore(self, parent):
if parent.isValid():
return False
return self.fileCount < len(self.fileList)
def fetchMore(self, parent):
if parent.isValid():
return
remainder = len(self.fileList) - self.fileCount
itemsToFetch = min(100, remainder)
if itemsToFetch <= 0:
return
self.beginInsertRows(QtCore.QModelIndex(), self.fileCount, self.fileCount + itemsToFetch - 1)
self.fileCount += itemsToFetch
self.endInsertRows()
self.emit(QtCore.SIGNAL("numberPopulated(int)"), itemsToFetch)
def setDirPath(self, path):
dir_ = QtCore.QDir(path)
self.beginResetModel()
self.fileList = dir_.entryList()
self.fileCount = 0
self.endResetModel()
if __name__ == '__main__':
app = QtWidgets.QApplication(sys.argv) if QtWidgets.QApplication.instance() is None else QtWidgets.QApplication.instance()
mainWin = Window()
mainWin.show()
sys.exit(app.exec_())
问题出在
data()
的最后一次返回中,它不应该返回0返回0时,视图或其委托尝试将值转换为适合该角色的类型,并且由于视图请求的第一个角色之一是大小提示(并且无法将返回的“0”转换为有效的大小提示),因此它不会请求任何其他数据:因为大小无效,该项被认为是隐藏的,因此不需要请求其他角色
只需删除
data()
末尾的return 0
,因为隐式的return
就足够了PS:您使用的
self.emit
语法被认为已经过时,请将其更改为self.numberPopulated.emit(itemsToFetch)
;此外,仅具有单个签名的信号不需要显式重载,因此您可以从textChanged
中删除["QString"]
,从numberPopulated
中删除[int]
。我还建议您在函数之间至少留一行空白,因为这样可以使代码更具可读性
我的回答将进一步解释musicamante's answer
QVariant是一种Qt/C++对象,允许处理各种类型的数据,但在python中,由于语言的动态类型,该对象类型不再是必需的,因此没有必要将其导出到python(尽管PyQt5有)。QVariant()生成了一个无效的QVariant,python等价物是None,因此
return QVariant()
可以转换为return None
或简单地return
同样可以颠倒,因为当返回{{4CD>}时,C++中转换为^ {< CD4}},然后转换为^ {CD6>},其含义与^ {CD7>}不同,因为第一个存储了0个,第二个不存储任何东西,因为它是无效的q变体。p>
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