PyQt5中已打开窗口与未打开窗口间的变量传递问题

你遇到的AttributeError核心原因有两个：

1. 子窗口的Ui_CalledWindow类从未定义过stringOut属性，主窗口的self.stringOut属于主窗口对象，子窗口无法直接访问；
2. 调用setupUi初始化子窗口时，变量还未传递给子窗口，就直接执行self.listView.addItem(self.stringOut)，导致属性不存在报错。

以下是两种可行的解决思路及代码修改：

方案1：修改子窗口setupUi方法，接收传递参数 #

直接在子窗口的初始化方法中添加参数，接收主窗口传递的字符串并初始化列表项：

修改后的calledWidget.py #

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_CalledWindow(object):
    # 新增string参数，默认值为None避免单独运行子窗口时报错
    def setupUi(self, Dialog, string=None):
        Dialog.setObjectName("Dialog")
        Dialog.resize(612, 178)
        Dialog.setWindowTitle("Dialog")
        
        self.verticalLayout = QtWidgets.QVBoxLayout(Dialog)
        self.verticalLayout.setObjectName("verticalLayout")
        
        self.listView = QtWidgets.QListWidget(Dialog)
        self.listView.setObjectName("listView")
        self.verticalLayout.addWidget(self.listView)
        
        # 仅当有传递字符串时才添加列表项
        if string:
            self.listView.addItem(string)
        
        self.buttonBox = QtWidgets.QDialogButtonBox(Dialog)
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Cancel|QtWidgets.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName("buttonBox")
        self.verticalLayout.addWidget(self.buttonBox)

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    Dialog = QtWidgets.QDialog()
    ui = Ui_CalledWindow()
    # 单独运行时可传入测试字符串
    ui.setupUi(Dialog, "测试字符串")
    Dialog.show()
    sys.exit(app.exec_())

修改后的mainWidget.py（passString方法部分） #

def passString(self):
    stringToPass = self.lineEdit.text()
    print(stringToPass)
    
    openingDialog = QMessageBox()
    openingDialog.setWindowTitle("Warning")
    openingDialog.setText("Are sure you want to pass the string: {}?".format(stringToPass))
    openingDialog.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
    reply = openingDialog.exec()
    
    if reply == QMessageBox.Yes:
        self.newWindow = QtWidgets.QDialog()
        self.ui = Ui_CalledWindow()
        # 调用setupUi时传递字符串参数
        self.ui.setupUi(self.newWindow, stringToPass)
        self.newWindow.show()

方案2：创建子窗口后直接操作其控件 #

无需修改子窗口的setupUi方法，在主窗口中完成子窗口初始化后，直接通过子窗口UI对象访问控件并添加内容：

修改后的mainWidget.py（passString方法部分） #

def passString(self):
    stringToPass = self.lineEdit.text()
    print(stringToPass)
    
    openingDialog = QMessageBox()
    openingDialog.setWindowTitle("Warning")
    openingDialog.setText("Are sure you want to pass the string: {}?".format(stringToPass))
    openingDialog.setStandardButtons(QMessageBox.Yes | QMessageBox.No)
    reply = openingDialog.exec()
    
    if reply == QMessageBox.Yes:
        self.newWindow = QtWidgets.QDialog()
        self.ui = Ui_CalledWindow()
        self.ui.setupUi(self.newWindow)
        # 直接操作子窗口的listView添加项
        self.ui.listView.addItem(stringToPass)
        self.newWindow.show()

修改后的calledWidget.py #

删除原代码中报错的self.listView.addItem(self.stringOut)行：

from PyQt5 import QtCore, QtGui, QtWidgets

class Ui_CalledWindow(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(612, 178)
        Dialog.setWindowTitle("Dialog")
        
        self.verticalLayout = QtWidgets.QVBoxLayout(Dialog)
        self.verticalLayout.setObjectName("verticalLayout")
        
        self.listView = QtWidgets.QListWidget(Dialog)
        self.listView.setObjectName("listView")
        self.verticalLayout.addWidget(self.listView)
        
        self.buttonBox = QtWidgets.QDialogButtonBox(Dialog)
        self.buttonBox.setOrientation(QtCore.Qt.Horizontal)
        self.buttonBox.setStandardButtons(QtWidgets.QDialogButtonBox.Cancel|QtWidgets.QDialogButtonBox.Ok)
        self.buttonBox.setObjectName("buttonBox")
        self.verticalLayout.addWidget(self.buttonBox)

if __name__ == "__main__":
    import sys
    app = QtWidgets.QApplication(sys.argv)
    Dialog = QtWidgets.QDialog()
    ui = Ui_CalledWindow()
    ui.setupUi(Dialog)
    Dialog.show()
    sys.exit(app.exec_())

两种方案各有适用场景：方案1适合需要在子窗口初始化阶段就使用参数的场景，方案2更灵活，适合初始化后动态传递数据的需求。

内容的提问来源于stack exchange，提问作者ARChalifour