如何使一个圆每秒钟都改变它的颜色？

Question

我最近做了一个红绿灯程序（图形用户界面），我不知道这是错误的，我不知道如何包括QTimer或任何延迟功能，使颜色变化，我尝试了显示功能，最终得到了两个程序，我真的不知道如何修复我的代码，你能帮我吗？你知道吗

import PyQt5, sys, time,os
from os import system,name
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import QPoint,QTimerEvent,QTimer,Qt
from PyQt5.QtWidgets import QWidget,QApplication,QMainWindow
from PyQt5.QtGui import QPainter
class Stoplight(QMainWindow):
    def __init__(self,parent = None):
        QWidget.__init__(self,parent)
        self.setWindowTitle("Stoplight")
        self.setGeometry(500,500,250,510)
    def paintEvent(self,event):
        radx = 50
        rady = 50
        center = QPoint(125,125)
        p = QPainter()
        p.begin(self)
        p.setBrush(Qt.white)
        p.drawRect(event.rect())
        p.end()

        p1 = QPainter()
        p1.begin(self)
        p1.setBrush(Qt.red)
        p1.setPen(Qt.black)
        p1.drawEllipse(center,radx,rady)
        p1.end()
class Stoplight1(Stoplight):
    def __init__(self,parent = None):
        QWidget.__init__(self,parent)
        self.setWindowTitle("Stoplight")
        self.setGeometry(500,500,250,510)
    def paintEvent(self,event):
        radx = 50
        rady = 50
        center = QPoint(125,125)
        p = QPainter()
        p.begin(self)
        p.setBrush(Qt.white)
        p.drawRect(event.rect())
        p.end()

        p1 = QPainter()
        p1.begin(self)
        p1.setBrush(Qt.green)
        p1.setPen(Qt.black)
        p1.drawEllipse(center,radx,rady)
        p1.end()
if __name__ == "__main__":
    application = QApplication(sys.argv)
    stoplight1 = Stoplight()
    stoplight2 = Stoplight1()
    time.sleep(1)
    stoplight1.show()
    time.sleep(1)
    stoplight2.show()
sys.exit(application.exec_())

Answer 1

这将是实现它的一个暗示。您需要定义一些函数或对象来处理循环的不同位置。此外，使用函数self.update()调用paintEvent和application.processEvents()使更改在gui中可见。您可以在执行部分使用代码，并从中生成更复杂的函数。你知道吗

编辑：使用字典尝试这种方法，因为它包含的代码较少。你知道吗

import PyQt5, sys, time,os
from os import system,name
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.QtCore import QPoint,QTimerEvent,QTimer,Qt
from PyQt5.QtWidgets import QWidget,QApplication,QMainWindow
from PyQt5.QtGui import QPainter
class Stoplight(QMainWindow):
    def __init__(self,parent = None):
        QWidget.__init__(self,parent)
        self.setWindowTitle("Stoplight")
        self.setGeometry(500,500,250,510)
        self.radx = 50
        self.rady = 50
        self.traffic_light_dic = {"red":{"QColor":Qt.red,
                                         "center":QPoint(125,125)},
                                  "yellow": {"QColor": Qt.yellow,
                                          "center": QPoint(125, 250)},
                                  "green": {"QColor": Qt.green,
                                          "center": QPoint(125, 375)},
                                  }
    def switch_to_color(self, color):
        self.center = self.traffic_light_dic[color]["center"]
        self.color = self.traffic_light_dic[color]["QColor"]
        self.update()
    def paintEvent(self, event):
        p = QPainter()
        p.begin(self)
        p.setBrush(self.color)
        p.setPen(Qt.black)
        p.drawEllipse(self.center, self.radx,self.rady)
        p.end()

if __name__ == "__main__":
    application = QApplication(sys.argv)
    stoplight1 = Stoplight()
    stoplight1.show()
    time.sleep(2)
    stoplight1.switch_to_color("red")
    application.processEvents()
    time.sleep(2)
    stoplight1.switch_to_color("yellow")
    application.processEvents()
    time.sleep(2)
    stoplight1.switch_to_color("green")
    application.processEvents()
    sys.exit(application.exec_())

Answer 2

尽管@f.wue的响应显然是不正确的，因为您不应该在GUI线程中使用time.sleep()，因为它会冻结应用程序，例如，在运行time.sleep()时尝试调整窗口大小。你知道吗

相反，您应该使用QTimer，正如您所说，计时器必须连接到更改颜色的函数，并调用间接调用paintEvent()事件的update()方法。由于希望颜色循环更改颜色，因此必须创建循环迭代器。你知道吗

from itertools import cycle
from PyQt5 import QtCore, QtGui, QtWidgets

class TrafficLight(QtWidgets.QMainWindow):
    def __init__(self,parent = None):
        super(TrafficLight, self).__init__(parent)
        self.setWindowTitle("TrafficLight ")
        self.traffic_light_colors = cycle([
            QtGui.QColor('red'),
            QtGui.QColor('yellow'),
            QtGui.QColor('green')
        ])
        self._current_color = next(self.traffic_light_colors)
        timer = QtCore.QTimer(
            self, 
            interval=2000, 
            timeout=self.change_color
        )
        timer.start()
        self.resize(200, 400)

    @QtCore.pyqtSlot()
    def change_color(self):
        self._current_color = next(self.traffic_light_colors)
        self.update()

    def paintEvent(self, event):
        p = QtGui.QPainter(self)
        p.setBrush(self._current_color)
        p.setPen(QtCore.Qt.black)
        p.drawEllipse(self.rect().center(), 50, 50)

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    w = TrafficLight()
    w.show() 
    sys.exit(app.exec_())