PyQt5：如何在子线程中运行 QTimer 并将值返回给主 Widget？

Question

我必须说这是一个初学者的问题。但是我尝试/搜索了很多但没有成功。

有一个QLabel，通过运行我希望将子线程中的值显示在上面的代码。

我也想在子线程中有QTimer，因为时间是在那里控制的（不是在主线程QThread）。

这是我想要实现的QLable上的效果...

0 (show for 1 second)
1 (show for 1 second)
2 (show for 1 second)
...
11 (show for 2 second)
12 (show for 2 second)
...
21 (show for 3 second)
22 (show for 3 second)
...

这是我的代码：

# -*- coding: utf-8 -*-

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *


class WorkerThread(QThread):

    def __init__(self, parent=None):
        super(WorkerThread, self).__init__(parent)
        self._running = False

        self.timer = QTimer()  # Question: define the QTimer here?
        self.timer.timeout.connect(self.doWork)
        self.timer.start(1000)

    def run(self):
        self._running = True
        while self._running:
            self.doWork()

    def doWork(self):
        for i in range(40):  # Question: How to return the i onto the QLable?
            if i <= 10: 
                # show the value of i on the QLabel and wait for 1 second
                pass
            elif i <= 20:
                # show the value of i on the QLable and wait for 2 second
                pass
            elif i <= 30:
                # show the value of i on the QLable and wait for 3 second
                pass
            else:
                # show the value of i on the QLable and wait for 4 second
                pass

    def stop(self, wait = False):
        self._running = False
        if wait:
            self.wait()


class MyApp(QWidget):
    def __init__(self, parent= None):
        super(MyApp, self).__init__(parent)
        self.thread = WorkerThread()
        self.initUI()

    def initUI(self):
        self.text = "hello world"
        self.setGeometry(100, 100, 500, 100)
        self.setWindowTitle('test')

        self.lbl_1 = QLabel("for every number between 0-10 wait 1 second, for 11-20 wait 2 sec, ...", self)

        self.show()


if __name__ == '__main__':
    app = QApplication(sys.argv)
    window = MyApp()
    window.show()
    sys.exit(app.exec_())

总结起来有两个问题： 1、如何在子线程中定义QTimer？ 2. 如何将子线程的值返回给QLabel？

感谢您的帮助！

Answer 1

不必使用QTimer 来执行您需要的任务，在线程中您可以有阻塞元素，例如QThead::sleep()，它会产生暂停。要发送信息，我们可以使用parent() 传递GUI，并将其与QMetaObject::invokeMethod() 结合，我们可以根据Qt 规则更新标签：

class WorkerThread(QThread):
    [...]    
    def doWork(self):
        for i in range(40):  # Question: How to return the i onto the QLable?
            if i <= 10:
                QThread.sleep(1)
            elif i <= 20:
                QThread.sleep(2)
            elif i <= 30:
                QThread.sleep(3)
            else:
                QThread.sleep(4)
            gui = self.parent()
            QMetaObject.invokeMethod(gui.lbl_1, "setText", Qt.QueuedConnection,
                                     Q_ARG(str, str(i)))

[...]    

class MyApp(QWidget):
    def __init__(self, parent=None):
        super(MyApp, self).__init__(parent) 
        self.thread = WorkerThread(self) # passing the window as a parent
        self.thread.start()
        self.initUI()

    def initUI(self):
        [...]

---

我们也可以将QTimer与QEventLoop一起使用，产生与QThread::sleep()相同的效果：

def doWork(self):
    for i in range(40):  # Question: How to return the i onto the QLable?
        if i <= 10:
            interval = 1000
        elif i <= 20:
            interval = 2000
        elif i <= 30:
            interval = 3000
        else:
            interval = 4000
        loop = QEventLoop()
        QTimer.singleShot(interval, loop.quit)
        loop.exec_()
        gui = self.parent()
        QMetaObject.invokeMethod(gui.lbl_1, "setText", Qt.QueuedConnection,
                                 Q_ARG(str, str(i)))

---

我们可以使用信号来代替QMetaObject::invokeMethod：

class WorkerThread(QThread):
    numberChanged = pyqtSignal(str)
    def __init__(self, parent=None):
        [...]

    def doWork(self):
        for i in range(40):  # Question: How to return the i onto the QLable?
            if i <= 10:
                interval = 1000
            elif i <= 20:
                interval = 2000
            elif i <= 30:
                interval = 3000
            else:
                interval = 4000
            loop = QEventLoop()
            QTimer.singleShot(interval, loop.quit)
            loop.exec_()
            self.numberChanged.emit(str(i))

[...]

class MyApp(QWidget):
    def __init__(self, parent=None):
        super(MyApp, self).__init__(parent)
        self.thread = WorkerThread(self)
        self.thread.start()
        self.initUI()

    def initUI(self):
        self.text = "hello world"
        self.setGeometry(100, 100, 500, 100)
        self.setWindowTitle('test')
        self.lbl_1 = QLabel("for every number between 0-10 wait 1 second, for 11-20 wait 2 sec, ...", self)
        self.thread.numberChanged.connect(self.lbl_1.setText, Qt.QueuedConnection)
        self.show()