python - Pyqt5 qthread + 信号不工作 + gui 卡住

Question

我正在尝试使用 imap lib 制作一个邮箱检查器，它在没有 gui 的情况下与 python、队列和多线程一起工作得很好。

但是当我尝试放置一个 gui 时，我制作的每个功能都会让 gui 卡住直到完成。

我尝试了各种文档(添加 qthread、signal、cursorr 等)和教程中的很多东西，但没有一个对我有用。

谁能帮助我理解如何在运行函数时设置文本或将文本附加到 QtextEdit，因为它只有在完成后才能工作。

这是我的代码:

class Checker(QtCore.QThread):
    signal = QtCore.pyqtSignal(object)

    def __init__(self, lignesmailtocheck):
        QtCore.QThread.__init__(self)
        self.lignesmailtocheck = lignesmailtocheck

    def run(self):
            lignemailtocheck = self.lignesmailtocheck.strip()                        
            maillo, passo = lignemailtocheck.split(":",1)
            debmail, finmail = maillo.split("@",1)
            setimap =["oultook.com:imap-mail.outlook.com", "gmail.com:imap.gmail.com"]
            for lignesimaptocheck in sorted(setimap):
                    ligneimaptocheck = lignesimaptocheck.strip()
                    fai, imap = ligneimaptocheck.split(":",1)                                
                    if finmail == fai:
                            passo0 = passo.rstrip()
                            try :
                                    mail = imaplib.IMAP4_SSL(imap)
                                    mail.login(maillo, passo)
                                    mailboxok = open("MailBoxOk.txt", "a+", encoding='utf-8', errors='ignore')
                                    mailboxok.write(maillo+":"+passo+"\n")
                                    mailboxok.close()
                                    totaly = maillo+":"+passo0+":"+imap                                
                                    print(maillo+":"+passo+"\n")

                                    self.send_text.emit(totaly)
                                    time.sleep(1)
                            except imaplib.IMAP4.error:                          
                                           print ("LOGIN FAILED!!! ")
class Ui_Form(object):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(400, 300)

        self.pushButton = QtWidgets.QPushButton(Form)
        self.pushButton.setGeometry(QtCore.QRect(150, 210, 75, 23))
        self.pushButton.setObjectName("pushButton")
        self.pushButton.clicked.connect(self.gogogo)

        self.openliste = QtWidgets.QToolButton(Form)
        self.openliste.setGeometry(QtCore.QRect(40, 110, 71, 21))
        self.openliste.setObjectName("openliste")

        self.textEdit = QtWidgets.QTextEdit(Form)
        self.textEdit.setGeometry(QtCore.QRect(170, 50, 201, 121))
        self.textEdit.setObjectName("textEdit")

        self.progressBar = QtWidgets.QProgressBar(Form)
        self.progressBar.setGeometry(QtCore.QRect(10, 260, 381, 23))
        self.progressBar.setValue(0)
        self.progressBar.setObjectName("progressBar")

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

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.pushButton.setText(_translate("Form", "PushButton"))
        self.openliste.setText(_translate("Form", "..."))

    def gogogo(self):

        mailtocheck = open('File/toCheck.txt', 'r', encoding='utf-8', errors='ignore').readlines()        
        setmailtocheck = set(mailtocheck)
        for lignesmailtocheck in sorted(setmailtocheck):
            checker = Checker(lignesmailtocheck)

            thread = QThread()
            checker.moveToThread(thread)
            # connections after move so cross-thread:
            thread.started.connect(checker.run)
            checker.signal.connect(self.checkedok)
            thread.start()

    def checkedok(self, data):
        print(data)
        self.textEdit.append(data)
if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    Form = QtWidgets.QWidget()
    ui = Ui_Form()
    ui.setupUi(Form)
    Form.show()
    sys.exit(app.exec_())

Answer 1

由于在 PyQt 中使用 QThread 时经常遇到类似问题，与您的类似，这里有一个示例来说明如何在 PyQt 中正确使用线程。我希望它可以作为类似问题的 goto-answer 有用，所以我花了比平时多一点的时间来准备这个。

该示例创建了许多工作对象，这些工作对象在非主线程中执行并通过 Qt 的异步信号与主(即 GUI)线程通信。

import time
import sys

from PyQt5.QtCore import QObject, QThread, pyqtSignal, pyqtSlot
from PyQt5.QtWidgets import QApplication, QPushButton, QTextEdit, QVBoxLayout, QWidget


def trap_exc_during_debug(*args):
    # when app raises uncaught exception, print info
    print(args)


# install exception hook: without this, uncaught exception would cause application to exit
sys.excepthook = trap_exc_during_debug


class Worker(QObject):
    """
    Must derive from QObject in order to emit signals, connect slots to other signals, and operate in a QThread.
    """

    sig_step = pyqtSignal(int, str)  # worker id, step description: emitted every step through work() loop
    sig_done = pyqtSignal(int)  # worker id: emitted at end of work()
    sig_msg = pyqtSignal(str)  # message to be shown to user

    def __init__(self, id: int):
        super().__init__()
        self.__id = id
        self.__abort = False

    @pyqtSlot()
    def work(self):
        """
        Pretend this worker method does work that takes a long time. During this time, the thread's
        event loop is blocked, except if the application's processEvents() is called: this gives every
        thread (incl. main) a chance to process events, which in this sample means processing signals
        received from GUI (such as abort).
        """
        thread_name = QThread.currentThread().objectName()
        thread_id = int(QThread.currentThreadId())  # cast to int() is necessary
        self.sig_msg.emit('Running worker #{} from thread "{}" (#{})'.format(self.__id, thread_name, thread_id))

        for step in range(100):
            time.sleep(0.1)
            self.sig_step.emit(self.__id, 'step ' + str(step))

            # check if we need to abort the loop; need to process events to receive signals;
            app.processEvents()  # this could cause change to self.__abort
            if self.__abort:
                # note that "step" value will not necessarily be same for every thread
                self.sig_msg.emit('Worker #{} aborting work at step {}'.format(self.__id, step))
                break

        self.sig_done.emit(self.__id)

    def abort(self):
        self.sig_msg.emit('Worker #{} notified to abort'.format(self.__id))
        self.__abort = True


class MyWidget(QWidget):
    NUM_THREADS = 5

    # sig_start = pyqtSignal()  # needed only due to PyCharm debugger bug (!)
    sig_abort_workers = pyqtSignal()

    def __init__(self):
        super().__init__()

        self.setWindowTitle("Thread Example")
        form_layout = QVBoxLayout()
        self.setLayout(form_layout)
        self.resize(400, 800)

        self.button_start_threads = QPushButton()
        self.button_start_threads.clicked.connect(self.start_threads)
        self.button_start_threads.setText("Start {} threads".format(self.NUM_THREADS))
        form_layout.addWidget(self.button_start_threads)

        self.button_stop_threads = QPushButton()
        self.button_stop_threads.clicked.connect(self.abort_workers)
        self.button_stop_threads.setText("Stop threads")
        self.button_stop_threads.setDisabled(True)
        form_layout.addWidget(self.button_stop_threads)

        self.log = QTextEdit()
        form_layout.addWidget(self.log)

        self.progress = QTextEdit()
        form_layout.addWidget(self.progress)

        QThread.currentThread().setObjectName('main')  # threads can be named, useful for log output
        self.__workers_done = None
        self.__threads = None

    def start_threads(self):
        self.log.append('starting {} threads'.format(self.NUM_THREADS))
        self.button_start_threads.setDisabled(True)
        self.button_stop_threads.setEnabled(True)

        self.__workers_done = 0
        self.__threads = []
        for idx in range(self.NUM_THREADS):
            worker = Worker(idx)
            thread = QThread()
            thread.setObjectName('thread_' + str(idx))
            self.__threads.append((thread, worker))  # need to store worker too otherwise will be gc'd
            worker.moveToThread(thread)

            # get progress messages from worker:
            worker.sig_step.connect(self.on_worker_step)
            worker.sig_done.connect(self.on_worker_done)
            worker.sig_msg.connect(self.log.append)

            # control worker:
            self.sig_abort_workers.connect(worker.abort)

            # get read to start worker:
            # self.sig_start.connect(worker.work)  # needed due to PyCharm debugger bug (!); comment out next line
            thread.started.connect(worker.work)
            thread.start()  # this will emit 'started' and start thread's event loop

        # self.sig_start.emit()  # needed due to PyCharm debugger bug (!)

    @pyqtSlot(int, str)
    def on_worker_step(self, worker_id: int, data: str):
        self.log.append('Worker #{}: {}'.format(worker_id, data))
        self.progress.append('{}: {}'.format(worker_id, data))

    @pyqtSlot(int)
    def on_worker_done(self, worker_id):
        self.log.append('worker #{} done'.format(worker_id))
        self.progress.append('-- Worker {} DONE'.format(worker_id))
        self.__workers_done += 1
        if self.__workers_done == self.NUM_THREADS:
            self.log.append('No more workers active')
            self.button_start_threads.setEnabled(True)
            self.button_stop_threads.setDisabled(True)
            # self.__threads = None

    @pyqtSlot()
    def abort_workers(self):
        self.sig_abort_workers.emit()
        self.log.append('Asking each worker to abort')
        for thread, worker in self.__threads:  # note nice unpacking by Python, avoids indexing
            thread.quit()  # this will quit **as soon as thread event loop unblocks**
            thread.wait()  # <- so you need to wait for it to *actually* quit

        # even though threads have exited, there may still be messages on the main thread's
        # queue (messages that threads emitted before the abort):
        self.log.append('All threads exited')


if __name__ == "__main__":
    app = QApplication([])

    form = MyWidget()
    form.show()

    sys.exit(app.exec_())

理解 PyQt 中的多线程编程所必需的主要概念如下:

• Qt 线程有自己的事件循环(特定于每个线程)。主线程，又名 GUI 线程，也是一个 QThread，它的事件循环由该线程管理。
• 线程之间的信号通过接收线程的事件循环进行(异步)传输。因此，GUI 或任何线程的响应能力 = 处理事件的能力。例如，如果一个线程在函数循环中很忙，它就不能处理事件，所以在函数返回之前它不会响应来自 GUI 的信号。
• 如果线程中的工作对象(方法)可能必须根据来自 GUI 的信号更改其操作过程(例如，中断循环或等待)，它必须调用 processEvents() QApplication 实例上的。这将允许 QThread 处理事件，从而调用槽以响应来自 GUI 的异步信号。请注意，QApplication.instance().processEvents() 似乎在每个线程上调用 processEvents()，如果不需要，则调用 QThread.currentThread()。 processEvents() 是一个有效的替代方法。
• 调用 QThread.quit() 不会立即退出其事件循环:它必须等待当前正在执行的槽(如果有)返回。因此，一旦线程被告知退出，您就必须对其执行 wait() 操作。因此，中止工作线程通常涉及向它发出信号(通过自定义信号)以停止它正在做的任何事情:这需要 GUI 对象上的自定义信号，该信号与工作槽的连接，并且工作线程的工作方法必须调用线程的 processEvents() 允许发出的信号在工作时到达插槽。