The QFileSystemModel doesn't load the contents of a directory until explicitly requested (in case of a tree view, it onyl happens when the directory is expanded the first time).
This requires to carefully verify and set the check state of each path recursively not only whenever a new file or directory is added (or renamed/removed), but also when the directory contents are actually loaded.
In order to correctly implement this, the check states should also be stored using file paths, because when the contents of a directory change some indexes might be invalidated.
The following implementation should take care of all written above, and emit a signal only when an item state is actively changed and the parent state is changed, but not for the children items of a checked directory.
While this choice might seem partially incoherent, it's a performance requirement, as you cannot get the individual signals for each subdirectory (nor you might want to): if you check the top level directory, you might receive thousands of unwanted notifications; on the other hand, it might be important to receive a notification if the parent directory state has changed, whenever all items become checked or unchecked.
from PyQt5 import QtCore, QtWidgets
class CheckableFileSystemModel(QtWidgets.QFileSystemModel):
checkStateChanged = QtCore.pyqtSignal(str, bool)
def __init__(self):
super().__init__()
self.checkStates = {}
self.rowsInserted.connect(self.checkAdded)
self.rowsRemoved.connect(self.checkParent)
self.rowsAboutToBeRemoved.connect(self.checkRemoved)
def checkState(self, index):
return self.checkStates.get(self.filePath(index), QtCore.Qt.Unchecked)
def setCheckState(self, index, state, emitStateChange=True):
path = self.filePath(index)
if self.checkStates.get(path) == state:
return
self.checkStates[path] = state
if emitStateChange:
self.checkStateChanged.emit(path, bool(state))
def checkAdded(self, parent, first, last):
# if a file/directory is added, ensure it follows the parent state as long
# as the parent is already tracked; note that this happens also when
# expanding a directory that has not been previously loaded
if not parent.isValid():
return
if self.filePath(parent) in self.checkStates:
state = self.checkState(parent)
for row in range(first, last + 1):
index = self.index(row, 0, parent)
path = self.filePath(index)
if path not in self.checkStates:
self.checkStates[path] = state
self.checkParent(parent)
def checkRemoved(self, parent, first, last):
# remove items from the internal dictionary when a file is deleted;
# note that this *has* to happen *before* the model actually updates,
# that's the reason this function is connected to rowsAboutToBeRemoved
for row in range(first, last + 1):
path = self.filePath(self.index(row, 0, parent))
if path in self.checkStates:
self.checkStates.pop(path)
def checkParent(self, parent):
# verify the state of the parent according to the children states
if not parent.isValid():
return
childStates = [self.checkState(self.index(r, 0, parent)) for r in range(self.rowCount(parent))]
newState = QtCore.Qt.Checked if all(childStates) else QtCore.Qt.Unchecked
oldState = self.checkState(parent)
if newState != oldState:
self.setCheckState(parent, newState)
self.dataChanged.emit(parent, parent)
self.checkParent(parent.parent())
def flags(self, index):
return super().flags(index) | QtCore.Qt.ItemIsUserCheckable
def data(self, index, role=QtCore.Qt.DisplayRole):
if role == QtCore.Qt.CheckStateRole and index.column() == 0:
return self.checkState(index)
return super().data(index, role)
def setData(self, index, value, role, checkParent=True, emitStateChange=True):
if role == QtCore.Qt.CheckStateRole and index.column() == 0:
self.setCheckState(index, value, emitStateChange)
for row in range(self.rowCount(index)):
# set the data for the children, but do not emit the state change,
# and don't check the parent state (to avoid recursion)
self.setData(index.child(row, 0), value, QtCore.Qt.CheckStateRole,
checkParent=False, emitStateChange=False)
self.dataChanged.emit(index, index)
if checkParent:
self.checkParent(index.parent())
return True
return super().setData(index, value, role)
class Test(QtWidgets.QWidget):
def __init__(self):
super().__init__()
layout = QtWidgets.QVBoxLayout(self)
self.tree = QtWidgets.QTreeView()
layout.addWidget(self.tree, stretch=2)
model = CheckableFileSystemModel()
model.setRootPath('')
self.tree.setModel(model)
self.tree.setSortingEnabled(True)
self.tree.header().setSectionResizeMode(QtWidgets.QHeaderView.Stretch)
self.logger = QtWidgets.QPlainTextEdit()
layout.addWidget(self.logger, stretch=1)
self.logger.setReadOnly(True)
model.checkStateChanged.connect(self.updateLog)
self.resize(640, 480)
QtCore.QTimer.singleShot(0, lambda: self.tree.expand(model.index(0, 0)))
def updateLog(self, path, checked):
if checked:
text = 'Path "{}" has been checked'
else:
text = 'Path "{}" has been unchecked'
self.logger.appendPlainText(text.format(path))
self.logger.verticalScrollBar().setValue(
self.logger.verticalScrollBar().maximum())
if __name__ == '__main__':
import sys
app = QtWidgets.QApplication(sys.argv)
test = Test()
test.show()
sys.exit(app.exec_())
