如何在Qthread中改变Qtimer的时间间隔？

问题描述 投票：0回答：1

我想在一个QThread中改变一个QTimer的间隔时间。这是我的代码。

import sys
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.QtCore import QObject, QTimer, QThread


class Worker(QObject):
    def __init__(self):
        QObject.__init__(self)
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.work)

    def start(self):
        self.timer.start(1000)

    def work(self):
        print("Hello World...")

    def set_interval(self, interval):
        self.timer.setInterval(interval)


def main():
    # Set up main window
    app = QApplication(sys.argv)
    win = QMainWindow()
    win.setFixedSize(200, 100)
    spinbox_interval = QtWidgets.QSpinBox(win)
    spinbox_interval.setMaximum(5000)
    spinbox_interval.setSingleStep(500)
    spinbox_interval.setValue(1000)

    worker = Worker()
    thread = QThread()
    worker.moveToThread(thread)
    thread.started.connect(worker.start)
    thread.start()

    def change_interval():
        value = spinbox_interval.value()
        worker.set_interval(value)

    spinbox_interval.valueChanged.connect(change_interval)

    win.show()
    sys.exit(app.exec_())


if __name__ == "__main__":
    main()

如果我在启动定时器后调用worker.setInterval()，超时信号不再发出信号。谁能给我解释一下我做错了什么？

python pyqt pyqt5 qthread qtimer
1个回答
1
投票

要了解这个问题，你必须在控制台CMD中运行以获得错误信息，从而了解原因，如果你这样做，你会得到以下错误信息。

QObject::killTimer: Timers cannot be stopped from another thread
QObject::startTimer: Timers cannot be started from another thread

要理解这个错误信息，你必须知道：

  • QObjects不是线程安全的，所以不能从另一个线程修改。
  • QObjects的子代与父代生活在同一个线程中。

所以作为Worker的子代的定时器就和它的父代一样生活在二级线程中，因此你不能从其他线程中修改它。在这种情况下，就是要在二级线程中发送修改信息，为此有几种选择。

  • QMetaObject.invokeMethod() 用 pyqtSlot:

    import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QSpinBox
from PyQt5.QtCore import pyqtSlot, QMetaObject, QObject, Qt, QTimer, QThread, Q_ARG


class Worker(QObject):
    def __init__(self):
        QObject.__init__(self)
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.work)

    def start(self):
        self.timer.start(1000)

    def work(self):
        print("Hello World...")

    @pyqtSlot(int)
    def set_interval(self, interval):
        self.timer.setInterval(interval)


def main():
    # Set up main window
    app = QApplication(sys.argv)
    win = QMainWindow()
    win.setFixedSize(200, 100)
    spinbox_interval = QSpinBox(win)
    spinbox_interval.setMaximum(5000)
    spinbox_interval.setSingleStep(500)
    spinbox_interval.setValue(1000)

    worker = Worker()
    thread = QThread()
    worker.moveToThread(thread)
    thread.started.connect(worker.start)
    thread.start()

    def change_interval():
        value = spinbox_interval.value()
        QMetaObject.invokeMethod(
            worker, "set_interval", Qt.QueuedConnection, Q_ARG(int, value)
        )

    spinbox_interval.valueChanged.connect(change_interval)

    win.show()
    ret = app.exec_()

    QMetaObject.invokeMethod(worker.timer, "stop")
    thread.quit()
    thread.wait()
    sys.exit(ret)


if __name__ == "__main__":
    main()

  • 自定义信号与槽。

    import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QSpinBox
from PyQt5.QtCore import pyqtSignal, pyqtSlot, QMetaObject, QObject, Qt, QTimer, QThread


class Worker(QObject):
    updateInterval = pyqtSignal(int)

    def __init__(self):
        QObject.__init__(self)
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.work)

        self.updateInterval.connect(self.set_interval)

    def start(self):
        self.timer.start(1000)

    def work(self):
        print("Hello World...")

    @pyqtSlot(int)
    def set_interval(self, interval):
        self.timer.setInterval(interval)


def main():
    # Set up main window
    app = QApplication(sys.argv)
    win = QMainWindow()
    win.setFixedSize(200, 100)
    spinbox_interval = QSpinBox(win)
    spinbox_interval.setMaximum(5000)
    spinbox_interval.setSingleStep(500)
    spinbox_interval.setValue(1000)

    worker = Worker()
    thread = QThread()
    worker.moveToThread(thread)
    thread.started.connect(worker.start)
    thread.start()

    def change_interval():
        value = spinbox_interval.value()
        worker.updateInterval.emit(value)

    spinbox_interval.valueChanged.connect(change_interval)

    win.show()
    ret = app.exec_()

    QMetaObject.invokeMethod(worker.timer, "stop")
    thread.quit()
    thread.wait()
    sys.exit(ret)


if __name__ == "__main__":
    main()

  • 自定义QEvent。

    import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QSpinBox
from PyQt5.QtCore import QEvent, QMetaObject, QObject, Qt, QTimer, QThread


class IntervalEvent(QEvent):
    def __init__(self, interval):
        QEvent.__init__(self, QEvent.User + 1000)
        self._interval = interval

    @property
    def interval(self):
        return self._interval


class Worker(QObject):
    def __init__(self):
        QObject.__init__(self)
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.work)

    def start(self):
        self.timer.start(1000)

    def work(self):
        print("Hello World...")

    def set_interval(self, interval):
        self.timer.setInterval(interval)

    def event(self, e):
        if isinstance(e, IntervalEvent):
            self.set_interval(e.interval)
        return Worker.event(self, e)


def main():
    # Set up main window
    app = QApplication(sys.argv)
    win = QMainWindow()
    win.setFixedSize(200, 100)
    spinbox_interval = QSpinBox(win)
    spinbox_interval.setMaximum(5000)
    spinbox_interval.setSingleStep(500)
    spinbox_interval.setValue(1000)

    worker = Worker()
    thread = QThread()
    worker.moveToThread(thread)
    thread.started.connect(worker.start)
    thread.start()

    def change_interval():
        value = spinbox_interval.value()
        event = IntervalEvent(value)
        QApplication.postEvent(worker, event)

    spinbox_interval.valueChanged.connect(change_interval)

    win.show()
    ret = app.exec_()

    QMetaObject.invokeMethod(worker.timer, "stop")
    thread.quit()
    thread.wait()
    sys.exit(ret)


if __name__ == "__main__":
    main()

  • QTimer.singleShot() 用 functools.partial() (只适用于PyQt5，不适用于PySide2)

    import sys
from functools import partial

from PyQt5.QtWidgets import QApplication, QMainWindow, QSpinBox
from PyQt5.QtCore import QMetaObject, QObject, Qt, QTimer, QThread


class Worker(QObject):
    def __init__(self):
        QObject.__init__(self)
        self.timer = QTimer(self)
        self.timer.timeout.connect(self.work)

    def start(self):
        self.timer.start(1000)

    def work(self):
        print("Hello World...")

    def set_interval(self, interval):
        print(interval)
        self.timer.setInterval(interval)


def main():
    # Set up main window
    app = QApplication(sys.argv)
    win = QMainWindow()
    win.setFixedSize(200, 100)
    spinbox_interval = QSpinBox(win)
    spinbox_interval.setMaximum(5000)
    spinbox_interval.setSingleStep(500)
    spinbox_interval.setValue(1000)

    worker = Worker()
    thread = QThread()
    worker.moveToThread(thread)
    thread.started.connect(worker.start)
    thread.start()

    def change_interval():
        value = spinbox_interval.value()
        wrapper = partial(worker.set_interval, value)
        QTimer.singleShot(0, wrapper)

    spinbox_interval.valueChanged.connect(change_interval)

    win.show()
    ret = app.exec_()

    QMetaObject.invokeMethod(worker.timer, "stop")
    thread.quit()
    thread.wait()
    sys.exit(ret)


if __name__ == "__main__":
    main()
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