为什么我可以在 PySide2 表 model 中发出 dataChanged()，但不能发出 layoutChanged()？

Question

我是 Qt 的新手。 目前，我正在尝试学习如何从不同的线程更新表 model，然后如何为其获取即时显示更新。 我阅读了文档并找到了dataChanged()和layoutChanged()信号。 虽然dataChanged()工作正常，但任何发出layoutChanged()的尝试都会失败：

'QObject::connect: Cannot queue arguments of type 'QList<QPersistentModelIndex>' (Make sure 'QList<QPersistentModelIndex>' is registered using qRegisterMetaType().)

搜索这个特定的错误并没有给我任何可以变成工作代码的东西。 我没有显式使用任何QList或QPersistentModelIndex ，但由于我选择的构造，当然可以隐式使用它们。

我究竟做错了什么？

class TimedModel(QtCore.QAbstractTableModel):

    def __init__(self, table, view):
        super(TimedModel, self).__init__()
        self.table = table
        self.view =  view
        self.setHeaderData(0, Qt.Horizontal, Qt.AlignLeft, Qt.TextAlignmentRole)
        self.rows = 6
        self.columns = 4
        self.step = 5
        self.timer = Thread(
            name = "Timer",
            target = self.tableTimer,
            daemon = True)
        self.timer.start()
        self.random = Random()
        self.updated = set()

    @staticmethod
    def encode(row, column):
        return row << 32 | column

    def data(self, index, role):

        if role == Qt.DisplayRole or role == Qt.EditRole:
            return f'Data-{index.row()}-{index.column()}'

        if role == Qt.ForegroundRole:
            encoded = TimedModel.encode(index.row(), index.column())
            return QBrush(Qt.red if encoded in self.updated else Qt.black)            

        return None

    def rowCount(self, index):
        return self.rows

    def columnCount(self, index):
        return self.columns

    def headerData(self, col, orientation, role):
        if orientation == Qt.Vertical:
            # Vertical
            return super().headerData(col, orientation, role)
        # Horizontal
        if not 0 <= col < self.columns:
            return None
        if role == Qt.DisplayRole:
            return f'Data-{col}'
        if role == Qt.TextAlignmentRole:
            return int(Qt.AlignLeft | Qt.AlignVCenter)
        return super().headerData(col, orientation, role)

    def tableTimer(self):
        while True:
            time.sleep(5.0)
            randomRow = self.random.randint(0, self.rows)
            randomColumn = self.random.randint(0, self.columns)
            encodedRandom = TimedModel.encode(randomRow, randomColumn)
            if encodedRandom in self.updated:
                self.updated.remove(encodedRandom)
            else:
                self.updated.add(encodedRandom)
            updatedIndex = self.createIndex(randomRow, randomColumn)
            self.dataChanged.emit(updatedIndex, updatedIndex)

            '''this here does not work:'''
            self.layoutAboutToBeChanged.emit()
            self.rows += self.step
            self.layoutChanged.emit()

class MainWindow(QtWidgets.QMainWindow):

    def __init__(self):
        QtWidgets.QMainWindow.__init__(self)

        self.timedTable = QTableView()
        self.model = TimedModel(self.timedTable, self)

        self.timedTable.setModel(self.model)
        headerView = self.timedTable.horizontalHeader()
        headerView.setStretchLastSection(True)
        self.setCentralWidget(self.timedTable)

        self.setGeometry(300, 300, 1000, 600)
        self.setWindowTitle('Timed Table')
        self.show()

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    app.name = "Timed Table Application"
    window = MainWindow()
    window.show()
    app.exec_()

Answer 1

以下代码：

self.layoutAboutToBeChanged.emit()
self.rows += self.step
self.layoutChanged.emit()

创建新的 model 元素，这些元素具有关联的QPersistentModelIndex不是线程安全的，并且 Qt 监视其创建以警告其滥用，因为在这种情况下修改该元素是不安全的，因为它意味着从另一个线程修改 GUI（阅读此处了解更多信息） .

因此，您会看到该消息警告您尝试执行的操作不安全。

相反， dataChanged只发出一个信号，不会创建任何属于 Qt 的元素，而且您很幸运，“self.updated”的修改没有产生瓶颈，因为您从辅助线程修改了属于主线程的属性而没有使用守卫作为互斥锁。

Qt 指出 GUI 和 GUI 使用的元素只能在 GUI 线程中更新，如果您想使用来自另一个线程的信息修改 GUI，那么您必须发送该信息，例如，使用是线程安全的：

import random
import sys
import threading
import time

from PySide2 import QtCore, QtGui, QtWidgets


class TimedModel(QtCore.QAbstractTableModel):
    random_signal = QtCore.Signal(object)

    def __init__(self, table, view):
        super(TimedModel, self).__init__()
        self.table = table
        self.view = view
        self.setHeaderData(
            0, QtCore.Qt.Horizontal, QtCore.Qt.AlignLeft, QtCore.Qt.TextAlignmentRole
        )
        self.rows = 6
        self.columns = 4
        self.step = 5
        self.updated = set()

        self.random_signal.connect(self.random_slot)

        self.timer = threading.Thread(name="Timer", target=self.tableTimer, daemon=True)
        self.timer.start()

    @staticmethod
    def encode(row, column):
        return row << 32 | column

    def data(self, index, role):

        if role in (QtCore.Qt.DisplayRole, QtCore.Qt.EditRole):
            return f"Data-{index.row()}-{index.column()}"

        if role == QtCore.Qt.ForegroundRole:
            encoded = TimedModel.encode(index.row(), index.column())
            return QtGui.QBrush(
                QtCore.Qt.red if encoded in self.updated else QtCore.Qt.black
            )

        return None

    def rowCount(self, index):
        return self.rows

    def columnCount(self, index):
        return self.columns

    def headerData(self, col, orientation, role):
        if orientation == QtCore.Qt.Vertical:
            # Vertical
            return super().headerData(col, orientation, role)
        # Horizontal
        if not 0 <= col < self.columns:
            return None
        if role == QtCore.Qt.DisplayRole:
            return f"Data-{col}"
        if role == QtCore.Qt.TextAlignmentRole:
            return QtCore.Qt.AlignLeft | QtCore.Qt.AlignVCenter
        return super().headerData(col, orientation, role)

    def tableTimer(self):
        while True:
            time.sleep(5.0)
            randomRow = random.randint(0, self.rows)
            randomColumn = random.randint(0, self.columns)
            encodedRandom = TimedModel.encode(randomRow, randomColumn)

            self.random_signal.emit(encodedRandom)

    @QtCore.Slot(object)
    def random_slot(self, encodedRandom):
        if encodedRandom in self.updated:
            self.updated.remove(encodedRandom)
        else:
            self.updated.add(encodedRandom)
        self.layoutAboutToBeChanged.emit()
        self.rows += self.step
        self.layoutChanged.emit()


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super().__init__(parent)

        self.timedTable = QtWidgets.QTableView()
        self.model = TimedModel(self.timedTable, self)

        self.timedTable.setModel(self.model)
        headerView = self.timedTable.horizontalHeader()
        headerView.setStretchLastSection(True)
        self.setCentralWidget(self.timedTable)

        self.setGeometry(300, 300, 1000, 600)
        self.setWindowTitle("Timed Table")
        self.show()


if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    app.name = "Timed Table Application"
    window = MainWindow()
    window.show()
    app.exec_()