PyQt：使用 QDataStream 保存本机 QTreeWidget
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【中文标题】PyQt：使用 QDataStream 保存本机 QTreeWidget【英文标题】：PyQt: Saving native QTreeWidgets using QDataStream 【发布时间】：2014-03-06 08:40:59 【问题描述】：我最近花了一些时间研究如何在 PyQt 中使用 QDataStream 和 QTreeWidget。我从来没有找到具体的例子来做到这一点，而且 QDataStream 的 pyqt 文档通常似乎非常稀缺。所以我想我会在这里发布一个问题作为面包屑路径，以防其他人需要提示。我会稍等片刻，以防有人想跳进去试一试，我会尽力回复。
问题是：在 PyQt 中，如何使用 QDataStream 将 QTreeWidgetItems 作为原生 QT 对象保存到文件中，然后将文件读回以完全恢复保存时的树结构？
埃里克
【问题讨论】：
【参考方案1】：在one of my other answers 的一个类似问题中，我写了一个简单的demo，可以序列化为xml。
相同的代码可以很容易地适应 QDataStream。我并不是真的推荐它作为解决方案（可能有几十种不同的方法可以实现相同的目标），但它至少提供了一个可行的示例：
import sip
sip.setapi('QString', 2)
from xml.etree import cElementTree as etree
from PyQt4 import QtGui, QtCore
class Window(QtGui.QWidget):
def __init__(self, xml):
QtGui.QWidget.__init__(self)
self.tree = QtGui.QTreeWidget(self)
self.tree.header().hide()
self.button = QtGui.QPushButton('Export', self)
self.button.clicked[()].connect(self.exportTree)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.tree)
layout.addWidget(self.button)
self._array = QtCore.QByteArray()
self._buffer = QtCore.QBuffer(self._array, self)
self._buffer.open(QtCore.QIODevice.ReadWrite)
self._datastream = QtCore.QDataStream(self._buffer)
self.importTree(xml)
def importTree(self, xml):
def build(item, root):
for element in root.getchildren():
child = QtGui.QTreeWidgetItem(item)
data = element.attrib['data'].encode('ascii')
self._array.swap(self._array.fromBase64(data))
self._buffer.reset()
self._datastream >> child
build(child, element)
item.setExpanded(True)
root = etree.fromstring(xml)
build(self.tree.invisibleRootItem(), root)
def exportTree(self):
def build(item, root):
for row in range(item.childCount()):
child = item.child(row)
self._array.clear()
self._buffer.reset()
self._datastream << child
data = self._array.toBase64().data().decode('ascii')
element = etree.SubElement(root, 'node', data=data)
build(child, element)
root = etree.Element('root')
build(self.tree.invisibleRootItem(), root)
from xml.dom import minidom
print(minidom.parseString(etree.tostring(root)).toprettyxml())
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Window("""\
<?xml version="1.0" ?>
<root>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB/////wAA
AAAAAAAAAAEAAAAKAAAAAAYAUgBlAGQ=">
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAP//
//8AAAAAAAEAAAAKAAAAAAgAQwB5AGEAbg==">
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAICA
AAAAAAAAAAEAAAAKAAAAAAoARwByAGUAZQBu"/>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAAAA
//8AAAAAAAEAAAAKAAAAAAgAQgBsAHUAZQ=="/>
</node>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB/////6Wl
AAAAAAAAAAEAAAAKAAAAAAwATwByAGEAbgBnAGU=">
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//+AgAAA
gIAAAAAAAAEAAAAKAAAAAAwAUAB1AHIAcABsAGU="/>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAICA
AAAAAAAAAAEAAAAKAAAAAAoARwByAGUAZQBu"/>
</node>
</node>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAP//
//8AAAAAAAEAAAAKAAAAAAgAQwB5AGEAbg==">
<node data="AAAAAQAAAAEAAAAJAAAAQwAB/////6Wl
AAAAAAAAAAEAAAAKAAAAAAwATwByAGEAbgBnAGU=">
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAP//
//8AAAAAAAEAAAAKAAAAAAgAQwB5AGEAbg=="/>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//+AgAAA
gIAAAAAAAAEAAAAKAAAAAAwAUAB1AHIAcABsAGU="/>
</node>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAICA
AAAAAAAAAAEAAAAKAAAAAAoARwByAGUAZQBu">
<node data="AAAAAQAAAAEAAAAJAAAAQwAB//8AAAAA
//8AAAAAAAEAAAAKAAAAAAgAQgBsAHUAZQ=="/>
<node data="AAAAAQAAAAEAAAAJAAAAQwAB/////wAA
AAAAAAAAAAEAAAAKAAAAAAYAUgBlAGQ="/>
</node>
</node>
</root>
""")
window.setGeometry(800, 300, 300, 300)
window.show()
sys.exit(app.exec_())
【讨论】：
【参考方案2】：我会继续展示我使用的方法。希望我在知道自己的问题如何解决方面没有不公平的优势:-)
如果有人对此有更清晰或更 Pythonic 的看法，欢迎跟进。谢谢！
import sys,os.path
from PyQt4 import QtGui, QtCore
class TreeExperiment(QtGui.QWidget):
def __init__(self,parent=None):
QtGui.QWidget.__init__(self,parent)
self.tree=QtGui.QTreeWidget(self) #
self.tree.setObjectName("treeWidget") #
self.add_button=QtGui.QPushButton("Add", self) # Initialize a simple
self.save_button=QtGui.QPushButton("Save", self) # form containing a
gridlayout = QtGui.QGridLayout(self) # treeWidget, an
gridlayout.addWidget(self.tree,1,0,1,9) # 'Add' button, and a
gridlayout.addWidget(self.add_button,2,0,2,3) # 'Save' button
gridlayout.addWidget(self.save_button,2,3,2,3) #
self.tree.headerItem().setText(0,"Label") #
if os.path.isfile('native_tree_save.qfile'):
# First look for a previously saved tree. If found, define
# it as a QFile named 'file', open it, and define a datastream
# to read from it.
#
# Each tree node is saved to and read from the file in pairs:
# first, the QTreeWidgetItem itself, then the number of children
# the item has so that the tree structure can be re-created
#
# The first item is added directly as the root for simplicity,
# and is sent to the function which begins the tree reconstruction
file = QtCore.QFile('native_tree_save.qfile')
file.open(QtCore.QIODevice.ReadOnly)
datastream = QtCore.QDataStream(file)
child=QtGui.QTreeWidgetItem(self.tree.invisibleRootItem())
child.read(datastream)
num_childs=datastream.readUInt32()
self.restore_item(datastream,child,num_childs)
else: # Otherwise if this is the first use, create a root item
new_item=QtGui.QTreeWidgetItem(self.tree)
self.tree.setCurrentItem(self.tree.topLevelItem(0))
self.tree.currentItem().setText(0,'root')
self.tree.setItemSelected(self.tree.topLevelItem(0),1)
self.tree.setCurrentItem(self.tree.topLevelItem(0))
self.connect(self.add_button, QtCore.SIGNAL("clicked()"), self.add_item)
self.connect(self.save_button, QtCore.SIGNAL("clicked()"), self.save_tree)
self.added_item_count=0
def add_item(self): # Adds an item to whatever is selected
self.added_item_count+=1
label=str(self.added_item_count)
new_item=QtGui.QTreeWidgetItem(self.tree.currentItem())
new_item.setText(0,label)
self.tree.setCurrentItem(new_item)
def restore_item(self,datastream,item,num_childs):
for i in range(0, num_childs):
child=QtGui.QTreeWidgetItem(item)
child.read(datastream)
num_childs=datastream.readUInt32()
self.restore_item(datastream,child,num_childs)
def save_item(self,item,datastream):
num_childs=item.childCount()
for i in range(0,num_childs):
child = item.child(i)
child.write(datastream)
num_childs=child.childCount()
datastream.writeUInt32(num_childs)
self.save_item(child,datastream)
def save_tree(self):
file = QtCore.QFile('native_tree_save.qfile')
file.open(QtCore.QIODevice.WriteOnly)
datastream = QtCore.QDataStream(file)
self.save_item(self.tree.invisibleRootItem(),datastream)
if __name__=='__main__':
app = QtGui.QApplication(sys.argv)
window = TreeExperiment()
window.resize(200, 120)
window.show()
sys.exit(app.exec_())
【讨论】：
【参考方案3】：QTreeWidget 是一个红鲱鱼。您要保存的是通用 QAbstractItemModel (treeWidget->model()) - 毕竟，QTreeWidget 是一个视图，并且具有内置模型。现在，这些模型的项目只是QVariants，这些只是 Python 类型，但也完全受到 QDataStream::operator<< 的支持。您只需要选择一个树遍历（深度优先、广度优先或其他），然后将树中的项目及其深度转储到流中。当您读取流时，这些信息足以重建树。
【讨论】：
谢谢——我同意，这是对解决方案的一个很好的描述，希望我在谈论 treeWidget 而不是它的项目时没有欺骗。我得出的解决方案完全正确，它依赖于存储项目并使用它们来填充新 treeWidget 的结构。你想提供几行python代码吗？我看到你在用 C++ 说话，但我无法让这些运算符工作。使用 QDataStream 功能是我花了一段时间才理解的技巧之一。 @EricMyers 明天会做，我偶尔会使用 Python。以上是关于PyQt：使用 QDataStream 保存本机 QTreeWidget的主要内容，如果未能解决你的问题，请参考以下文章