Question

我在Designer（pyqt5）中创建了一个GUI。我的主类中的函数需要在单独的线程上工作。我还在操作期间在QtextEdit LIVE上捕获了stdout。到目前为止，一切都有效。

现在我正在尝试将ProgressBar实现到我的主GUI表单上。该栏需要像textEdit一样显示实时进展。

以下示例代码适用于Linux，没有任何警告。但在Windows上我得到错误：

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

我知道这是因为我在我的线程函数中修改了ui元素。我做了我的研究，但所有答案都指向使用QThreads（就在我开始理解基本线程的时候！）。我更喜欢一种更新GUI的方法，而无需更改下面的当前线程系统。

以下是示例代码：

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()

ui：

# -*- 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"))

不知怎的，我需要-instantly-通知gui线程（来自我正在运行的线程）进度条值正在改变（一个可能需要几分钟才能完成的进程）。

Answer 1

定义将更新发送到进度条的自定义信号：

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)
            ...

从Python线程更新PyQt GUI

1 个答案: