PyQt5 多线程

Question

为什么代码不起作用？视频工作文件，当我尝试在第二个标签中显示文本时，它也会显示出来。但是如果我想像 setText() 中的当前时间一样连续更改值，我该怎么办？我是多线程新手。

import sys
import cv2
from PyQt5.QtCore import QThread, pyqtSignal, Qt
from PyQt5.QtGui import QPixmap, QImage
from PyQt5.QtWidgets import QApplication, QWidget, QLabel
import datetime


class App(QWidget):
    def __init__(self):
        super().__init__()
        self.title = 'PyQt5 Video'
        self.left = 100
        self.top = 100
        self.width = 640
        self.height = 480
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.resize(1800, 1200)
        # create a label
        label = QLabel(self)
        label.move(280, 120)
        label.resize(640, 480)
        label1 = QLabel(self)
        label1.move(680, 820)
        th = Thread(self)
        th.changePixmap.connect(lambda p: label.setPixmap(p))
        th.changeLabel.connect(lambda n:label1.setText("A"))
        th.start()

class Thread(QThread):
    changePixmap = pyqtSignal(QPixmap)
    changeLabel = pyqtSignal(QLabel)

    def __init__(self, parent=None):
        QThread.__init__(self, parent=parent)

    def run(self):
        cap = cv2.VideoCapture(0)
        n=QLabel()
        while True:
            ret, frame = cap.read()
            rgbImage = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
            convertToQtFormat = QImage(rgbImage.data, rgbImage.shape[1], rgbImage.shape[0], QImage.Format_RGB888)
            convertToQtFormat = QPixmap.fromImage(convertToQtFormat)
            p = convertToQtFormat.scaled(640, 480, Qt.KeepAspectRatio)
            self.changePixmap.emit(p)
            now = datetime.datetime.now()
            sec = now.second
            try:
                self.changeLabel.emit(n)
            except Exception as e:
                print(str(e))

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

Answer 1

您不应将新的小部件 (QLabel) 发送到主视图，因为这将是一个新标签，而不是原始标签，您应该发送 str 类型的文本。

class Thread(QThread):
    changePixmap = pyqtSignal(QPixmap)
    changeLabel = pyqtSignal(str)

    def run(self):
        [...]
        now = datetime.datetime.now()
        sec = now.second
        self.changeLabel.emit(str(sec))

然后连接到setText函数：

th.changeLabel.connect(label1.setText)

完整代码：

import sys
import cv2
from PyQt5.QtCore import QThread, pyqtSignal, Qt
from PyQt5.QtGui import QPixmap, QImage
from PyQt5.QtWidgets import QApplication, QWidget, QLabel
import datetime


class App(QWidget):
    def __init__(self):
        super().__init__()
        self.title = 'PyQt5 Video'
        self.left = 100
        self.top = 100
        self.width = 640
        self.height = 480
        self.initUI()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.resize(1800, 1200)
        # create a label
        # create a label
        label = QLabel(self)
        label.move(280, 120)
        label.resize(640, 480)
        label1 = QLabel(self)
        label1.move(580, 620)
        self.th = Thread(self)
        self.th.changePixmap.connect(label.setPixmap)
        self.th.changeLabel.connect(label1.setText)
        self.th.start()

    def closeEvent(self, event):
        self.th.stop()
        QWidget.closeEvent(self, event)

class Thread(QThread):
    changePixmap = pyqtSignal(QPixmap)
    changeLabel = pyqtSignal(str)

    def __init__(self, parent=None):
        QThread.__init__(self, parent=parent)
        self.isRunning = True

    def run(self):
        cap = cv2.VideoCapture(0)
        while self.isRunning:
            ret, frame = cap.read()
            rgbImage = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
            convertToQtFormat = QImage(rgbImage.data, rgbImage.shape[1], rgbImage.shape[0], QImage.Format_RGB888)
            convertToQtFormat = QPixmap.fromImage(convertToQtFormat)
            p = convertToQtFormat.scaled(640, 480, Qt.KeepAspectRatio)
            self.changePixmap.emit(p)
            now = datetime.datetime.now()
            sec = now.second
            self.changeLabel.emit(str(sec))

    def stop(self):
        self.isRunning = False
        self.quit()
        self.wait()


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

注意：我添加了 stop 方法来停止线程并正确关闭，为此我还覆盖了 closeEvent 方法。另一个变化，我移动了 label1，因为我的屏幕不是那么大。