Python-PyQt : Memory issue with QThread

Question

我想构建一个 Qt 界面来控制相机采集。

我想要什么: 在进入硬件通信之前，我正在测试一个控制“假相机”的 GUI，这是一个连续循环，如果启动，每 100 毫秒给出一个随机图像。图像采集在单独的线程中运行，以便用户可以与 GUI 交互。用户可以通过按钮开始和停止采集。

我想如何做到这一点: 我的第一次尝试是简单地 istanziate QThread并调用run()方法，然后将包含一个无限循环，其中单个图像采集由 QThread.sleep(0.1) 交错。 。我注意到在停止并重新启动线程后，程序开始滞后并在一段时间后崩溃。 通过阅读周围的一些帖子和主要Qt webpage ，然后我了解到，做我想做的事情的更好方法是:

subclass a QObject to create a worker. Instantiate this worker object and a QThread. Move the worker to the new thread.

此外，遵循this中的想法帖子中，我添加了一个QTimer对象无限地迭代线程内的工作线程，我实现了 active如果设置为False，则仅使线程运行而不执行任何操作的标志。 这个解决方案一开始似乎有效。我可以根据需要多次启动、停止和重新启动采集。

问题:

1) 当相机没有获取数据时，CPU 总是占用相当多的资源(根据 Windows 任务管理器，在我的情况下约为 30%)。

2)有时，在开始采集后，内存开始被填充，就像每个新图像都分配在新内存中一样(虽然我猜它应该被覆盖)，直到程序变得无响应，然后崩溃。 下图是发生这种情况时我在任务管理器中看到的内容: 红色箭头对应于采集开始的时间。

我哪里做错了？这是正确的处理方式吗？

代码

from PyQt5 import QtCore, QtWidgets
import sys
import numpy as np
import matplotlib
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg


class MyWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle('MyWindow')
        self._main = QtWidgets.QWidget()
        self.setCentralWidget(self._main) 

        # generate matplotlib canvas
        self.fig = matplotlib.figure.Figure(figsize=(4,4))
        self.canvas = FigureCanvasQTAgg(self.fig)
        self.ax = self.fig.add_subplot(1,1,1)
        self.im = self.ax.imshow(np.zeros((1000, 1000)), cmap='viridis')
        self.im.set_clim(vmin=0,vmax=1) 
        self.canvas.draw()

        # Add widgets and build layout
        self.startcambutton = QtWidgets.QPushButton('Start', checkable=True)
        self.startcambutton.released.connect(self.acquire)
        self.contincheck = QtWidgets.QCheckBox("Continuous")
        self.contincheck.clicked.connect(self.continuous_acquisition)
        self.contincheck.setChecked(True)
        layout = QtWidgets.QGridLayout(self._main)
        layout.addWidget(self.canvas, 0, 0)
        layout.addWidget(self.startcambutton, 1, 0)
        layout.addWidget(self.contincheck, 2, 0)

        # Initialize worker and timer and moveToThread
        self.fake_camera_thread = QtCore.QThread()
        self.fake_camera_timer = QtCore.QTimer()
        self.fake_camera_timer.setInterval(0)
        self.fake_camera_worker = FakeCamera(self)
        self.fake_camera_worker.moveToThread(self.fake_camera_thread)
        self.fake_camera_timer.timeout.connect(self.fake_camera_worker.acquire)
        self.fake_camera_thread.started.connect(self.fake_camera_timer.start)
        self.fake_camera_thread.finished.connect(self.fake_camera_worker.deleteLater)
        self.fake_camera_thread.finished.connect(self.fake_camera_timer.deleteLater)
        self.fake_camera_thread.finished.connect(self.fake_camera_thread.deleteLater)
        self.fake_camera_thread.start()

        self.camera_thread = self.fake_camera_thread
        self.camera = self.fake_camera_worker
        self.camera.image.connect(self.image_acquired)

    def continuous_acquisition(self):
        if self.contincheck.isChecked(): self.startcambutton.setCheckable(True)
        else: self.startcambutton.setCheckable(False)

    def acquire(self):
        if self.startcambutton.isCheckable() and not self.startcambutton.isChecked():
            self.startcambutton.setText('Start')
            self.contincheck.setEnabled(True)
        elif self.startcambutton.isCheckable() and self.startcambutton.isChecked():
            self.startcambutton.setText('Stop')
            self.contincheck.setDisabled(True)
        self.camera.toggle()

    @QtCore.pyqtSlot(object)
    def image_acquired(self, image):
        self.im.set_data(image)
        self.canvas.draw()


    def closeEvent(self, event):
        """ If window is closed """
        self.closeApp()
        event.accept() # let the window close

    def closeApp(self):
        """ close program """
        self.camera_thread.quit()
        self.camera_thread.wait()
        self.close()
        return



class FakeCamera(QtCore.QObject):
    image = QtCore.pyqtSignal(object)

    def __init__(self, parent):
        QtCore.QObject.__init__(self)
        self.parent = parent
        self.active = False

    def toggle(self):
        self.active = not self.active

    def acquire(self):
        """ this is the method running indefinitly in the associated thread """
        if self.active:
            self.new_acquisition()

    def new_acquisition(self):
        noise = np.random.normal(0, 1, (1000, 1000))
        self.image.emit(noise)
        if not self.parent.startcambutton.isChecked():
            self.active = False
        QtCore.QThread.sleep(0.1)



if __name__ == '__main__':
    app = QtCore.QCoreApplication.instance()
    if app is None:
        app = QtWidgets.QApplication(sys.argv)
    mainGui = MyWindow()
    mainGui.show()
    app.aboutToQuit.connect(app.deleteLater)
    app.exec_()

Answer 1

QThread.sleep() 只接受整个参数，当传递一个 float 时，它将对其进行四舍五入，在您的情况下 0.1 将四舍五入为 0，因此没有暂停，因此信号将是连续发出，但绘画需要一段时间，因此数据将存储在队列中，以增加内存。另一方面，如果QTimer要连续调用一个任务，最好驻留在处理该任务的对象的线程中，这样QTimer就足够了> 是 FakeCamera 的儿子。另一个改进是使用装饰器 @QtCore.pyqtSlot()，因为连接是在 C++ 中给出的，使其更加高效。最后，我改进了设计，因为 FakeCamera 不应该直接与 GUI 交互，因为如果你想将它与另一个 GUI 一起使用，你将不得不修改大量代码，最好创建插槽.

from PyQt5 import QtCore, QtWidgets
import numpy as np
import matplotlib
from matplotlib.backends.backend_qt5agg import FigureCanvasQTAgg


class MyWindow(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle('MyWindow')
        self._main = QtWidgets.QWidget()
        self.setCentralWidget(self._main) 

        # generate matplotlib canvas
        self.fig = matplotlib.figure.Figure(figsize=(4,4))
        self.canvas = FigureCanvasQTAgg(self.fig)
        self.ax = self.fig.add_subplot(1,1,1)
        self.im = self.ax.imshow(np.zeros((1000, 1000)), cmap='viridis')
        self.im.set_clim(vmin=0,vmax=1) 
        self.canvas.draw()

        # Add widgets and build layout
        self.startcambutton = QtWidgets.QPushButton('Start', checkable=True)
        self.startcambutton.released.connect(self.acquire)
        self.contincheck = QtWidgets.QCheckBox("Continuous")
        self.contincheck.toggled.connect(self.startcambutton.setCheckable)
        self.contincheck.setChecked(True)
        layout = QtWidgets.QGridLayout(self._main)
        layout.addWidget(self.canvas, 0, 0)
        layout.addWidget(self.startcambutton, 1, 0)
        layout.addWidget(self.contincheck, 2, 0)

        # Initialize worker and timer and moveToThread
        fake_camera_thread = QtCore.QThread(self)
        self.fake_camera_worker = FakeCamera()
        self.fake_camera_worker.moveToThread(fake_camera_thread)
        self.startcambutton.toggled.connect(self.fake_camera_worker.setState)
        self.fake_camera_worker.image.connect(self.image_acquired)
        fake_camera_thread.started.connect(self.fake_camera_worker.start)
        fake_camera_thread.finished.connect(self.fake_camera_worker.deleteLater)
        fake_camera_thread.finished.connect(fake_camera_thread.deleteLater)
        fake_camera_thread.start()

    @QtCore.pyqtSlot()
    def acquire(self):
        if self.startcambutton.isCheckable():
            text = "Stop" if self.startcambutton.isChecked() else "Start"
            self.startcambutton.setText(text)
            self.contincheck.setEnabled(not self.startcambutton.isChecked())

    @QtCore.pyqtSlot(object)
    def image_acquired(self, image):
        self.im.set_data(image)
        self.canvas.draw()


class FakeCamera(QtCore.QObject):
    image = QtCore.pyqtSignal(object)

    def __init__(self, parent=None):
        super(FakeCamera, self).__init__(parent)
        self.active = False
        self.fake_camera_timer = QtCore.QTimer(self, interval=0)
        self.fake_camera_timer.timeout.connect(self.acquire)

    @QtCore.pyqtSlot()
    def start(self):
        self.fake_camera_timer.start()

    @QtCore.pyqtSlot(bool)
    def setState(self, state):
        self.active = state

    @QtCore.pyqtSlot()
    def toggle(self):
        self.active = not self.active

    @QtCore.pyqtSlot()
    def acquire(self):
        """ this is the method running indefinitly in the associated thread """
        if self.active:
            self.new_acquisition()
        QtCore.QThread.msleep(100)

    def new_acquisition(self):
        noise = np.random.normal(0, 1, (1000, 1000))
        self.image.emit(noise)


if __name__ == '__main__':
    import sys
    app = QtCore.QCoreApplication.instance()
    if app is None:
        app = QtWidgets.QApplication(sys.argv)
    mainGui = MyWindow()
    mainGui.show()
    app.aboutToQuit.connect(app.deleteLater)
    sys.exit(app.exec_())