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multithreading - 从 Python 线程更新 PyQt GUI

问题描述

我有一个用 Designer (pyqt5) 制作的 GUI。我的主类中的一个函数需要在一个单独的线程上工作。在操作期间，我还在 QtextEdit LIVE 上捕获了标准输出。到目前为止一切正常。

现在我正在尝试在我的主 GUI 表单上实现 ProgressBar。该栏需要像在 textEdit 上一样显示实时进度。

下面的示例代码在 Linux 上运行，没有任何警告。但是在 Windows 上我得到了错误：

QObject::setParent: Cannot set parent, new parent is in a different thread

我知道这是因为我在线程函数中进行了 ui 元素修改。我进行了研究，但所有答案都指向使用 QThreads（就在我开始了解基本线程时！）。我希望有一种方法来更新我的 GUI，而不必更改下面的当前线程系统。

这是示例代码：

import sys
import threading
import time

from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtCore import QObject, pyqtSignal
from PyQt5.QtGui import QTextCursor

from ui_form import Ui_Form


class EmittingStream(QObject):
    textWritten = pyqtSignal(str)

    def write(self, text):
        self.textWritten.emit(str(text))


class Form(QMainWindow):
    finished = pyqtSignal()

    def __init__(self, parent=None):
        super(Form, self).__init__(parent)

        # Install the custom output stream
        sys.stdout = EmittingStream(textWritten=self.normalOutputWritten)

        self.ui = Ui_Form()
        self.ui.setupUi(self)

        self.ui.pushButton_run.clicked.connect(self.start_task)
        self.finished.connect(self.end_task)

    def start_task(self):

        self.thread = threading.Thread(target=self.run_test)
        self.thread.start()
        self.ui.pushButton_run.setEnabled(False)

    def end_task(self):
        self.ui.pushButton_run.setEnabled(True)

    def __del__(self):
        # Restore sys.stdout
        sys.stdout = sys.__stdout__

    def normalOutputWritten(self, text):
        """Append text to the QTextEdit."""
        cursor = self.ui.textEdit.textCursor()
        cursor.movePosition(QTextCursor.End)
        cursor.insertText(text)
        self.ui.textEdit.setTextCursor(cursor)
        self.ui.textEdit.ensureCursorVisible()

    def run_test(self):
        for i in range(100):
            per = i + 1
            self.ui.progressBar.setValue(per)
            print("%%%s" % per)
            time.sleep(0.15)  # simulating expensive task

        print("Task Completed!")
        time.sleep(1.5)
        self.ui.progressBar.reset()
        self.finished.emit()


def main():
    app = QApplication(sys.argv)
    form = Form()
    form.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

用户界面：

# -*- coding: utf-8 -*-
# Form implementation generated from reading ui file 'form.ui'
#
# Created: Mon Apr 30 13:43:19 2018
#      by: PyQt5 UI code generator 5.2.1
#
# WARNING! All changes made in this file will be lost!

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(800, 600)
        self.centralwidget = QtWidgets.QWidget(Form)
        self.centralwidget.setObjectName("centralwidget")
        self.pushButton_run = QtWidgets.QPushButton(self.centralwidget)
        self.pushButton_run.setGeometry(QtCore.QRect(40, 20, 311, 191))
        self.pushButton_run.setObjectName("pushButton_run")
        self.textEdit = QtWidgets.QTextEdit(self.centralwidget)
        self.textEdit.setGeometry(QtCore.QRect(40, 230, 721, 241))
        self.textEdit.setObjectName("textEdit")
        self.progressBar = QtWidgets.QProgressBar(self.centralwidget)
        self.progressBar.setGeometry(QtCore.QRect(40, 490, 721, 23))
        self.progressBar.setObjectName("progressBar")
        Form.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(Form)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 25))
        self.menubar.setObjectName("menubar")
        Form.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(Form)
        self.statusbar.setObjectName("statusbar")
        Form.setStatusBar(self.statusbar)

        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "MainWindow"))
        self.pushButton_run.setText(_translate("Form", "RUN"))

不知何故，我需要立即通知 gui 线程（从我正在运行的线程）进度条值正在更改（可能需要几分钟才能完成的过程）。

标签： multithreadingpython-3.xprogress-barpyqt5

解决方案

定义一个向进度条发送更新的自定义信号：

class Form(QMainWindow):
    finished = pyqtSignal()
    updateProgress = pyqtSignal(int)

    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        ...
        self.updateProgress.connect(self.ui.progressBar.setValue)

    def run_test(self):
        for i in range(100):
            per = i + 1
            self.updateProgress.emit(per)
            ...

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