如何在PyQt/Python中切换布局？（高级）

Question

更新 1:

在做了以下更改后：

from PyQt4 import QtGui, QtCore
class LoginWidget(QtGui.QWidget):
    success = QtCore.pyqtSignal() # Might be QtCore.pyqtSignal
    def __init__(self, parent=None):
        super(LoginWidget, self).__init__(parent)
        self.Username = QtGui.QLineEdit(self)  
        self.Password = QtGui.QLineEdit(self)
        self.buttonLogin = QtGui.QPushButton('Login', self)
        self.buttonLogin.clicked.connect(self.handleLogin)
        loginLayout = QtGui.QFormLayout()
        loginLayout.addRow("Username", self.Username) 
        loginLayout.addRow("Password", self.Password)
        layout = QtGui.QVBoxLayout(self)
        layout.addLayout(loginLayout)
        layout.addWidget(self.Username)
        layout.addWidget(self.Password)
        layout.addWidget(self.buttonLogin)
    def handleLogin(self):
        if (self.Username.text() == 'example' and
            self.Password.text() == 'example'):
            self.success.emit()
            # OR you know that the main window is the parent of this class
            # so you could call self.parent().P_3()
            # Signals are better though
        else:
            QtGui.QMessageBox.warning(
                self, 'Error', 'Incorrect Username/Password combination!')

class Page3(QtGui.QWidget):
    def __init__(self, parent=None):
        super(Page3, self).__init__(parent)
        layout = QtGui.QHBoxLayout()
        self.Hello = QtGui.QLabel('Hello')
        layout.addWidget(self.Hello)
        self.setLayout(layout)

class page1(QtGui.QWidget):
    def __init__(self, parent=None):
        super(page1, self).__init__(parent)
        layout = QtGui.QHBoxLayout()
        self.nextpage = QtGui.QPushButton('Page2')
        layout.addWidget(self.nextpage)
        self.setLayout(layout)

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.central_widget = QtGui.QStackedWidget()
        self.setCentralWidget(self.central_widget)
        Page1 = page1(self)
        Page1.nextpage.clicked.connect(self.P_2)
        self.central_widget.addWidget(Page1)
    def P_2(self):
        page2 = LoginWidget(self)

        # Connect your signal to a method. When success is emitted it will call P_3()
        page2.success.connect(self.P_3) # Note: P_3 does not have "()" with it

        self.central_widget.addWidget(page2)
        self.central_widget.setCurrentWidget(page2)
    def P_3(self):
        print("yay")
        page3 = Page3(self)
        # self.central_widget.addWidget(Page3) # you are calling the class (lowercase)
        # self.central_widget.setCurrentWidget(Page3) # calling the class (lowercase)
        self.central_widget.addWidget(Page3)
        self.central_widget.setCurrentWidget(Page3)

if __name__ == '__main__':
    User = ''
    app = QtGui.QApplication([])
    window = MainWindow()
    window.showFullScreen()
    app.exec_()

我遇到了这个错误：

错误追踪（最近的调用最后）： 文件 "C:\Users\Hamzah\My Documents\Work\A-Level\USB Stuff\Pie Chart 2.py"，第 66 行，在 P_3 self.central_widget.addWidget(Page3) 类型错误：QStackedWidget.addWidget(QWidget)：参数 1 的类型不符合预期 'PyQt4.QtCore.pyqtWrapperType'

问题：

下面的代码展示了如何在页面 1、登录页面（页面 2）和页面 3 之间切换布局。但是我似乎无法从页面 2 切换到页面 3。不过，我可以从页面 1 切换到页面 2！顺便提一下，当你运行程序时（如果你在运行的话），登录信息是 'example' 和 'example'，或者查看代码获取详细信息：

from PyQt4 import QtCore, QtGui

class MainWindow(QtGui.QMainWindow):
    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)
        self.central_widget = QtGui.QStackedWidget()
        self.setCentralWidget(self.central_widget)
        Page1 = page1(self)
        Page1.nextpage.clicked.connect(self.P_2)
        self.central_widget.addWidget(Page1)
    def P_2(self):
        page2 = LoginWidget(self)
        self.central_widget.addWidget(page2)
        self.central_widget.setCurrentWidget(page2)
    def P_3(self):
        print("Why won't the page open!!!???")
        page3 = Page3(self)
        self.central_widget.addWidget(Page3)
        self.central_widget.setCurrentWidget(Page3)

class LoginWidget(QtGui.QWidget):
    def __init__(self, parent=None):
        super(LoginWidget, self).__init__(parent)
        self.Username = QtGui.QLineEdit(self)  
        self.Password = QtGui.QLineEdit(self)
        self.buttonLogin = QtGui.QPushButton('Login', self)
        self.buttonLogin.clicked.connect(self.handleLogin)
        loginLayout = QtGui.QFormLayout()
        loginLayout.addRow("Username", self.Username) 
        loginLayout.addRow("Password", self.Password)
        layout = QtGui.QVBoxLayout(self)
        layout.addLayout(loginLayout)
        layout.addWidget(self.Username)
        layout.addWidget(self.Password)
        layout.addWidget(self.buttonLogin)
    def handleLogin(self):
        if (self.Username.text() == 'example' and
            self.Password.text() == 'example'):
            MainWindow().P_3()
        else:
            QtGui.QMessageBox.warning(
                self, 'Error', 'Incorrect Username/Password combination!')

class page1(QtGui.QWidget):
    def __init__(self, parent=None):
        super(page1, self).__init__(parent)
        layout = QtGui.QHBoxLayout()
        self.nextpage = QtGui.QPushButton('Page2')
        layout.addWidget(self.nextpage)
        self.setLayout(layout)

class Page3(QtGui.QWidget):
    def __init__(self, parent=None):
        super(Page3, self).__init__(parent)
        layout = QtGui.QHBoxLayout()
        self.Hello = QtGui.QLabel('Hello')
        layout.addWidget(self.Hello)
        self.setLayout(layout)

if __name__ == '__main__':
    User = ''
    app = QtGui.QApplication([])
    window = MainWindow()
    window.showFullScreen()
    app.exec_()

Answer 1

问题出在你的 LoginWidget 上。handleLogin 正在创建一个新的主窗口，并试图调用第3页。

你不需要创建一个新的主窗口，也不需要在登录时有一个主窗口的实例。

我建议使用信号。

class LoginWidget(QtGui.QWidget):
    success = QtCore.Signal() # Might be QtCore.pyqtSignal

    ...
    def handleLogin(self):
        if (self.Username.text() == 'example' and
            self.Password.text() == 'example'):
            self.success.emit()
            # OR you know that the main window is the parent of this class
            # so you could call self.parent().P_3()
            # Signals are better though
        else:
            QtGui.QMessageBox.warning(
                self, 'Error', 'Incorrect Username/Password combination!')

class MainWindow(QtGui.QMainWindow):
    def P_2(self):
        page2 = LoginWidget(self)

        # Connect your signal to a method. When success is emitted it will call P_3()
        page2.success.connect(self.P_3) # Note: P_3 does not have "()" with it

        self.central_widget.addWidget(page2)
        self.central_widget.setCurrentWidget(page2)

如果你在信号中需要传递参数，可以使用 lambda 函数。

page2.success.connect(lambda arg="": method(arg))

另外，注意 P_3 中的错误。

def P_3(self):
    page3 = Page3(self)
    # self.central_widget.addWidget(Page3) # you are calling the class (lowercase)
    # self.central_widget.setCurrentWidget(Page3) # calling the class (lowercase)

    self.central_widget.addWidget(page3)
    self.central_widget.setCurrentWidget(page3)