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python - 使用 concurrent.futures.ThreadPoolExecutor() 时的 PyQt5 小部件 Qthread 问题

问题描述

我一直在尝试使用concurrent.futures.ThreadPoolExecutor()来在我的应用程序中运行一些后台任务，以便在这些任务（“测量”）运行时能够与 GUI 进行交互。完成这些任务后，我分配一个回调函数来更新 GUI 的某些字段，然后尝试根据这些字段更新 GUI 小部件（绘图、表格、列表等）。

这是一个例子：

class MainWindow(QtWidgets.QMainWindow):
    
    def __init__(self):
        super(MainWindow, self).__init__()
        *some more code goes here*
        self.executor = concurrent.futures.ThreadPoolExecutor(max_workers=1)

    def perform_measurement():
        future = self.executor.submit(*a function*)
        future.add_done_callback(self.update_gui_fields)

    def update_gui_fields(self, future):
        data = future.result()
        self.items_for_list.append(QStandardItem(data['key']))
        *more fields are updated here*

        self.QListView1.setModel(self.items_for_list)
        *more widgets are updated here*

问题是这些字段正常更新，但是当我尝试与小部件交互时，应用程序崩溃了。这是因为子项（此处为self.items_for_list）与父项（此处 ）处于不同的线程中self.QListView1。这是我得到的错误：

QObject: Cannot create children for a parent that is in a different thread.
(Parent is QListView(0x555795efbc10), parent's thread is QThread(0x555795296600), current thread is QThread(0x7fd12400a100)
QBasicTimer::start: QBasicTimer can only be used with threads started with QThread

我在以前的帖子中找不到任何解决方案。知道如何攻击这个吗？谢谢！

标签： pythonpyqt5qthreadthreadpoolexecutor

解决方案

与 add_done_callback 关联的回调在辅助线程中执行，并且根据您的代码，您尝试从该辅助线程更新 GUI，这是被禁止的，因此 Qt 会引发该警告。解决方案是通过创建一个通过信号转发该信息的 QObject 来实现逻辑：

import concurrent.futures
import sys
import time

from PyQt5 import QtCore, QtGui, QtWidgets


def measure():
    time.sleep(5)
    return {"key": "value"}


class TaskManager(QtCore.QObject):
    finished = QtCore.pyqtSignal(object)

    def __init__(self, parent=None, max_workers=None):
        super().__init__(parent)
        self._executor = concurrent.futures.ThreadPoolExecutor(max_workers=max_workers)

    @property
    def executor(self):
        return self._executor

    def submit(self, fn, *args, **kwargs):
        future = self.executor.submit(fn, *args, **kwargs)
        future.add_done_callback(self._internal_done_callback)

    def _internal_done_callback(self, future):
        data = future.result()
        self.finished.emit(data)


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
        self.model = QtGui.QStandardItemModel()
        self.view = QtWidgets.QListView()
        self.view.setModel(self.model)

        self.button = QtWidgets.QPushButton("launch")

        self._manager = TaskManager(max_workers=1)
        self._manager.finished.connect(self.update_gui_fields)

        self.button.clicked.connect(self.perform_measurement)

        central_widget = QtWidgets.QWidget()
        self.setCentralWidget(central_widget)
        lay = QtWidgets.QVBoxLayout(central_widget)
        lay.addWidget(self.view)
        lay.addWidget(self.button)

    def perform_measurement(self):
        self._manager.submit(measure)

    def update_gui_fields(self, data):
        self.model.appendRow(QtGui.QStandardItem(data["key"]))


if __name__ == "__main__":

    app = QtWidgets.QApplication(sys.argv)
    w = MainWindow()
    w.show()
    sys.exit(app.exec_())

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