将信号发射到线程

Question

我正在使用PYQT5创建图形用户界面。 我想在执行一定过程时将信号发送到运行线程以更改参数。

我创建了一个简单的代码来演示我打算实现的目标。 下面的代码生成带有两个按钮的基本GUI。 按下第一个按钮时，创建并启动了一个线程，该线程每秒都会打印一个字符串。按下第二个按钮时，将修改显示的字符串并用另一个字符串替换。

我的问题是字符串永远不会更改，我不确定为什么。

import sys
from time import sleep

from PyQt5.QtCore import Qt, QMutex
from PyQt5.QtWidgets import (
    QApplication,
    QLabel,
    QMainWindow,
    QPushButton,
    QVBoxLayout,
    QWidget,
)

from PyQt5.QtCore import QObject, QThread, pyqtSignal

class Worker(QObject):
    finished = pyqtSignal()

    def __init__(self, parent=None):
        super(Worker, self).__init__()
        self.mutex = QMutex()
        self.stringToDisplay = 'Holà'

    def update(newStringToDisplay):
        self.mutex.lock()
        self.stringToDisplay = newStringToDisplay
        self.mutex.unlock()

    def run(self):
        """Long-running task."""
        while 1:
            sleep(1)
            self.mutex.lock()
            print(self.stringToDisplay)
            self.mutex.unlock()

        self.finished.emit()


class Window(QMainWindow):

    updateSignal = pyqtSignal(str)

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

    def setupUi(self):
        self.setWindowTitle("GUI")
        self.resize(300, 150)
        self.button2runThread = QPushButton('Click to start the thread', self)
        self.button2runThread.clicked.connect(self.runThread)

        self.button2updateParams = QPushButton('Click to update parameter in the running thread', self)
        self.button2updateParams.clicked.connect(self.updateThread)

        layout = QVBoxLayout()
        layout.addWidget(self.button2runThread)
        layout.addWidget(self.button2updateParams)
        
        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        self.centralWidget.setLayout(layout)

    def updateThread(self):
        self.updateSignal.emit('My new string')

    def runThread(self):
        self.thread = QThread()
        self.worker = Worker()
        self.worker.moveToThread(self.thread)
        self.thread.started.connect(self.worker.run)
        self.worker.finished.connect(self.thread.quit)
        self.worker.finished.connect(self.worker.deleteLater)
        self.thread.finished.connect(self.thread.deleteLater)
        
        self.updateSignal.connect(self.worker.update)

        self.thread.start()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    win = Window()
    win.show()
    sys.exit(app.exec())

Answer 1

我能够指出这个问题。
在将工人移至线程之前，我将信号连接起来。

这是导致问题的代码的一部分：

    self.thread = QThread()
    self.worker = Worker()

    self.worker.moveToThread(self.thread) # 1
    # ...
    # ...
    self.updateSignal.connect(self.worker.update) # must be called before 1

以及完整的代码：

import sys
from time import sleep

from PyQt5.QtCore import Qt, QMutex
from PyQt5.QtWidgets import (
    QApplication,
    QLabel,
    QMainWindow,
    QPushButton,
    QVBoxLayout,
    QWidget,
)

from PyQt5.QtCore import QObject, QThread, pyqtSignal

class Worker(QObject):
    finished = pyqtSignal()

    def __init__(self, parent=None):
        super(Worker, self).__init__()
        self.mutex = QMutex()
        self.stringToDisplay = 'Holà'

    def update(self, newStringToDisplay):
        self.mutex.lock()
        self.stringToDisplay = newStringToDisplay
        self.mutex.unlock()


    def run(self):
        """Long-running task."""
        while 1:
            sleep(1)
            self.mutex.lock()
            print(self.stringToDisplay)
            self.mutex.unlock()

        self.finished.emit()


class Window(QMainWindow):

    updateSignal = pyqtSignal(str)

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

    def setupUi(self):
        self.setWindowTitle("GUI")
        self.resize(300, 150)
        self.button2runThread = QPushButton('Click to start the thread', self)
        self.button2runThread.clicked.connect(self.runThread)

        self.button2updateParams = QPushButton('Click to update parameter in the running thread', self)
        self.button2updateParams.clicked.connect(self.updateThread)

        layout = QVBoxLayout()
        layout.addWidget(self.button2runThread)
        layout.addWidget(self.button2updateParams)
        
        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        self.centralWidget.setLayout(layout)

    
    def updateThread(self):
        self.updateSignal.emit('My new string')
    def runThread(self):
        self.thread = QThread()
        self.worker = Worker()

        self.updateSignal.connect(self.worker.update)

        self.worker.moveToThread(self.thread)
        self.thread.started.connect(self.worker.run)
        self.worker.finished.connect(self.thread.quit)
        self.worker.finished.connect(self.worker.deleteLater)
        self.thread.finished.connect(self.thread.deleteLater)
        
        

        self.thread.start()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    win = Window()
    win.show()
    sys.exit(app.exec())