QtWidgets.QStackedWidget()的意外行为

Question

我想使用pyqt5创建一个GUI，它在两个窗口(即WindowA和WindowB )之间来回切换。为了达到这个目的，我

• 为WindowA创建了一个类，为WindowB创建了另一个类，每个类中都有一个按钮
• 创建一个mainWindow类，它实例化一个类型为WindowA的对象和另一个类型为WindowB的对象，并将这两个对象添加到堆栈中。根据pyqt文档的说法

“QStackedWidget类提供了一个小部件堆栈，每次只能看到一个小部件。”

• 在mainWindow类中定义两个方法，LaunchA和LaunchB，分别使用setCurrentWidget()方法将当前小部件设置为A或B，并在单击按钮时调用另一个方法。

头几次，效果很好。我点击按钮A，它带来窗口B。我点击按钮B，它带我回到窗口A。但是在那之后它开始注册多次点击，就好像我一次点击了当前按钮和所有先前显示的按钮。我不知道怎么解决这个问题。这是一个(最小的？)可再现的例子，显示了问题。我还实现了一个函数，它计算按下按钮的次数，这样您就可以看到预期结果和实际结果之间的差异。

import sys 
from PyQt5 import QtWidgets, QtCore
from PyQt5.Qt import QAction, QMenu


class WindowA(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(WindowA, self).__init__(parent)
        self.buttonA = QtWidgets.QPushButton("Button A - Press me!")
        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.buttonA)
        self.buttonA.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
        layout.setContentsMargins(0,0,0,0)
        layout.setSpacing(1)
        self.setLayout(layout)
    def whenButtonPressed(self, count):
        print("Button A pressed. Total buttons pressed: " + str(count))

class WindowB(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(WindowB, self).__init__(parent)
        self.buttonB = QtWidgets.QPushButton("Button B - Press me!")
        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.buttonB)
        self.buttonB.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
        layout.setContentsMargins(0,0,0,0)
        layout.setSpacing(1)
        self.setLayout(layout)
    def whenButtonPressed(self, count):
        print("Button B pressed. Total buttons pressed: " + str(count))

class mainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(mainWindow, self).__init__(parent)
        self.setGeometry(850, 250, 300, 150)
        self.count = 0
        # Instantiating the classes of each window and adding them to the stack
        self.__A = WindowA()
        self.__B = WindowB()
        self.__stack = QtWidgets.QStackedWidget(self)
        self.__stack.addWidget(self.__A)
        self.__stack.addWidget(self.__B)
        self.__stack.setContentsMargins(1,1,1,1)
        self.setCentralWidget(self.__stack)
        self.launchA()
    def launchA(self):
        self.__stack.setCurrentWidget(self.__A)
        self.__stack.currentWidget().buttonA.clicked.connect(lambda: self.printAndChange())
        self.show()
    def launchB(self):
        self.__stack.setCurrentWidget(self.__B)
        self.__stack.currentWidget().buttonB.clicked.connect(lambda: self.printAndChange())
        self.show()
    def printAndChange(self):
        self.count += 1
        self.__stack.currentWidget().whenButtonPressed(self.count)
        if isinstance(self.__stack.currentWidget(), WindowA) == True : 
            self.launchB()
        elif isinstance(self.__stack.currentWidget(), WindowA) == False:
            self.launchA()


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle('Fusion')
    w = mainWindow()
    sys.exit(app.exec_())

Answer 1

你在错误的地方连接对象-信号插槽。试一试：

import sys 
from PyQt5 import QtWidgets, QtCore
from PyQt5.Qt import QAction, QMenu


class WindowA(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(WindowA, self).__init__(parent)
        self.buttonA = QtWidgets.QPushButton("Button A - Press me!")
        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.buttonA)
        self.buttonA.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
        layout.setContentsMargins(0,0,0,0)
        layout.setSpacing(1)
        self.setLayout(layout)
        
    def whenButtonPressed(self, count):
        print("Button A pressed. Total buttons pressed: " + str(count))


class WindowB(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(WindowB, self).__init__(parent)
        self.buttonB = QtWidgets.QPushButton("Button B - Press me!")
        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.buttonB)
        self.buttonB.setSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Preferred)
        layout.setContentsMargins(0,0,0,0)
        layout.setSpacing(1)
        self.setLayout(layout)
        
    def whenButtonPressed(self, count):
        print("Button B pressed. Total buttons pressed: " + str(count))


class MainWindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        
        self.setGeometry(850, 250, 300, 150)
        self.count = 0
        # Instantiating the classes of each window and adding them to the stack
        self.__A = WindowA()
        self.__A.buttonA.clicked.connect(lambda: self.printAndChange())       # +++
                
        self.__B = WindowB()
        self.__B.buttonB.clicked.connect(lambda: self.printAndChange())       # +++
        
        self.__stack = QtWidgets.QStackedWidget(self)
        self.__stack.addWidget(self.__A)
        self.__stack.addWidget(self.__B)
        self.__stack.setContentsMargins(1, 1, 1, 1)
        self.setCentralWidget(self.__stack)
        self.launchA()
        
    def launchA(self):
        self.__stack.setCurrentWidget(self.__A)
#        self.__stack.currentWidget().buttonA.clicked.connect(lambda: self.printAndChange())
        self.show()
        
    def launchB(self):
        self.__stack.setCurrentWidget(self.__B)
#        self.__stack.currentWidget().buttonB.clicked.connect(lambda: self.printAndChange())
        self.show()
        
    def printAndChange(self):
        self.count += 1
        self.__stack.currentWidget().whenButtonPressed(self.count)
        if isinstance(self.__stack.currentWidget(), WindowA) == True : 
            self.launchB()
        elif isinstance(self.__stack.currentWidget(), WindowA) == False:
            self.launchA()


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle('Fusion')
    w = MainWindow()
    sys.exit(app.exec_())