等待相机拍摄时显示消息

Question

我想在等待相机捕获时向用户显示加载消息。

程序在python中（使用opencv库和pyqt5 gui）

def monitoringActivity(self):
    print("monitoringActivity")

    self.monitoringToogle = not self.monitoringToogle

    if(self.monitoringToogle == True):
        qImg = QImage("loading.png")
        self.label.setPixmap(QtGui.QPixmap(qImg))
        self.pushButton_4.setText("Stop Monitoring")
        cap = cv2.VideoCapture(0)
        while (self.monitoringToogle == True):
            ret, frame = cap.read()
            frame = imutils.resize(frame, width=400)
            height, width, channel = frame.shape
            bytesPerLine = width*channel
            qImg = QImage(frame.copy().data, width, height, bytesPerLine, QImage.Format_RGB888)
            qImg = qImg.rgbSwapped()
            self.label.setPixmap(QtGui.QPixmap(qImg))
            key = cv2.waitKey(1) & 0xFF
            if key == ord("q"):
                breakpoint
        cap.release()
    else:
        self.pushButton_4.setText("Monitoring")
        qImg = QImage("white_background.png")
        self.label.setPixmap(QtGui.QPixmap(qImg))

此处的代码使图片成为“ loading.png”

qImg = QImage("loading.png")
self.label.setPixmap(QtGui.QPixmap(qImg))

但在显示摄像机框架之前不执行：

self.label.setPixmap(QtGui.QPixmap(qImg))