在 PyQt 的第二个线程中打开子对话框的正确方法是什么? [英] What is the proper way of opening a child dialog in a second thread in PyQt?
问题描述
我有一个应用程序，我在第二个线程中运行某个进程，并且在某个时间点，在特定条件下，另一个对话框窗口打开，该窗口会暂停进程，直到您确认某些内容.这会导致以下错误消息:
I have an application where I run some process in a second thread and at some point, given a certain condition, another dialog window opens, which halts the process until you confirm something. This causes the following error message:
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QApplication(0x1f9c82383d0), parent's thread is QThread(0x1f9c7ade2a0), current thread is QThread(0x1f9c8358800)
有趣的是，如果您还在进程运行时将光标移到 MainWindow 上，并且在新对话框弹出之前，它也会多次生成此错误消息:
Interestingly, if you also move your cursor over the MainWindow while the process is running, and before the new dialog pops up, it also produces this error message a couple of times:
QBasicTimer::stop: Failed. Possibly trying to stop from a different thread
很奇怪.因为它仅发生在您将光标移到 MainWindow 上时.
Very strange. Because it only occurs if you move your cursor over the MainWindow.
现在，在我的应用程序中，我实际上为使用 PyQt5.uic.loadUi 弹出的新对话框加载了一个界面，这并没有引起任何问题.但是，当我为这篇文章创建示例时，发生了另一个问题，因为我在初始化期间设置了新对话框的布局:
Now, in my application, I actually load an interface for the new dialog that pops up using PyQt5.uic.loadUi, and this hasn't caused any problems. However, when I was creating the example for this post, another issue occurred, due to the fact that I was setting the layout of the new dialog during its initialization:
QObject::setParent: Cannot set parent, new parent is in a different thread
导致应用程序崩溃:
Process finished with exit code -1073741819 (0xC0000005)
关于线程，我显然在这里做错了，但我不知道是什么.我特别困惑的是，我无法在初始化期间设置新对话框的布局，而使用 loadUi 完全没问题.这是我的示例代码:
I'm obviously doing something wrong here regarding the threading I would guess, but I don't know what. I am especially baffled by the fact that I cannot set the layout of the new dialog during its initialization, while using loadUi is totally fine. Here is my example code:
import sys
import time
import numpy as np
from PyQt5.QtCore import QObject, pyqtSignal, QThread
from PyQt5.QtWidgets import (
QDialog, QApplication, QPushButton, QGridLayout, QProgressBar, QLabel
)
class SpecialDialog(QDialog):
def __init__(self):
super().__init__()
btn = QPushButton('pass variable')
btn.clicked.connect(self.accept)
layout = QGridLayout()
layout.addWidget(btn)
# self.setLayout(layout)
self.variable = np.random.randint(0, 100)
class Handler(QObject):
progress = pyqtSignal(int)
finished = pyqtSignal(int)
def __init__(self):
super().__init__()
self._isRunning = True
self._success = False
def run(self):
result = None
i = 0
while i < 100 and self._isRunning:
if i == 50:
dialog = SpecialDialog()
dialog.exec_()
result = dialog.variable
time.sleep(0.01)
i += 1
self.progress.emit(i)
if i == 100:
self._success = True
self.finished.emit(result)
def stop(self):
self._isRunning = False
class MainWindow(QDialog):
def __init__(self):
super().__init__()
btn = QPushButton('test')
btn.clicked.connect(self.run_test)
self.pbar = QProgressBar()
self.resultLabel = QLabel('Result:')
layout = QGridLayout(self)
layout.addWidget(btn)
layout.addWidget(self.pbar)
layout.addWidget(self.resultLabel)
self.setLayout(layout)
self.handler = None
self.handler_thread = QThread()
self.result = None
def run_test(self):
self.handler = Handler()
self.handler.moveToThread(self.handler_thread)
self.handler.progress.connect(self.progress)
self.handler.finished.connect(self.finisher)
self.handler_thread.started.connect(self.handler.run)
self.handler_thread.start()
def progress(self, val):
self.pbar.setValue(val)
def finisher(self, result):
self.result = result
self.resultLabel.setText(f'Result: {result}')
self.pbar.setValue(0)
self.handler.stop()
self.handler.progress.disconnect(self.progress)
self.handler.finished.disconnect(self.finisher)
self.handler_thread.started.disconnect(self.handler.run)
self.handler_thread.terminate()
self.handler = None
if __name__ == '__main__':
app = QApplication(sys.argv)
GUI = MainWindow()
GUI.show()
sys.exit(app.exec_())
编辑
我忘了说我已经找到了 this post，这可能与我的问题有关，但是，我不理解顶级答案中解决方案的推理，更重要的是，我不会说我认为是 C++ 的内容.>
I forgot to mention that I already found this post, which may be related to my problem, however, I don't undestand the reasoning of the solution in the top answer, and more importantly, I don't speak what I believe is C++.
推荐答案
您无法从辅助线程创建或修改 GUI 元素，错误消息会提示这种情况.
You cannot create or modify a GUI element from a secondary thread and this is signaled by the error message.
您必须重新设计 Handler 类，根据您的要求，您必须将 run 分为 2 个方法，第一个方法将生成高达 50% 的进度，其中 GUI 将打开对话框，获取结果并启动第二个方法.
You have to redesign the Handler class, with your requirement you must divide run into 2 methods, the first method will generate progress up to 50% where the GUI will open the dialogue, obtain the result and launch the second method.
import sys
import time
import numpy as np
from functools import partial
from PyQt5.QtCore import QObject, pyqtSignal, pyqtSlot, QThread, QTimer
from PyQt5.QtWidgets import (
QDialog,
QApplication,
QPushButton,
QGridLayout,
QProgressBar,
QLabel,
)
class SpecialDialog(QDialog):
def __init__(self):
super().__init__()
btn = QPushButton("pass variable")
btn.clicked.connect(self.accept)
layout = QGridLayout()
layout.addWidget(btn)
# self.setLayout(layout)
self.variable = np.random.randint(0, 100)
class Handler(QObject):
progress = pyqtSignal(int)
finished = pyqtSignal(int)
def __init__(self):
super().__init__()
self._isRunning = True
self._success = False
@pyqtSlot()
def task1(self):
i = 0
while i <= 50 and self._isRunning:
time.sleep(0.01)
i += 1
self.progress.emit(i)
@pyqtSlot(int)
def task2(self, result):
i = 50
while i < 100 and self._isRunning:
time.sleep(0.01)
i += 1
self.progress.emit(i)
if i == 100:
self._success = True
self.finished.emit(result)
def stop(self):
self._isRunning = False
class MainWindow(QDialog):
def __init__(self):
super().__init__()
btn = QPushButton("test")
btn.clicked.connect(self.run_test)
self.pbar = QProgressBar()
self.resultLabel = QLabel("Result:")
layout = QGridLayout(self)
layout.addWidget(btn)
layout.addWidget(self.pbar)
layout.addWidget(self.resultLabel)
self.setLayout(layout)
self.handler = None
self.handler_thread = QThread()
self.result = None
def run_test(self):
self.handler = Handler()
self.handler.moveToThread(self.handler_thread)
self.handler.progress.connect(self.progress)
self.handler.finished.connect(self.finisher)
self.handler_thread.started.connect(self.handler.task1)
self.handler_thread.start()
@pyqtSlot(int)
def progress(self, val):
self.pbar.setValue(val)
if val == 50:
dialog = SpecialDialog()
dialog.exec_()
result = dialog.variable
wrapper = partial(self.handler.task2, result)
QTimer.singleShot(0, wrapper)
def finisher(self, result):
self.result = result
self.resultLabel.setText(f"Result: {result}")
self.pbar.setValue(0)
self.handler.stop()
self.handler_thread.quit()
self.handler_thread.wait()
if __name__ == "__main__":
app = QApplication(sys.argv)
GUI = MainWindow()
GUI.show()
sys.exit(app.exec_())
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