I have an example of QStacked Widget code from internet, which generates its own layout for each child (below)
import sys from PyQt4.QtCore import * from PyQt4.QtGui import * class stackedExample(QWidget): def __init__(self): super(stackedExample, self).__init__() self.leftlist = QListWidget() self.leftlist.insertItem(0, 'Contact') self.leftlist.insertItem(1, 'Personal') self.leftlist.insertItem(2, 'Educational') self.stack1 = QWidget() self.stack2 = QWidget() self.stack3 = QWidget() self.stack1UI() self.stack2UI() self.stack3UI() self.Stack = QStackedWidget(self) self.Stack.addWidget(self.stack1) self.Stack.addWidget(self.stack2) self.Stack.addWidget(self.stack3) hbox = QHBoxLayout(self) hbox.addWidget(self.leftlist) hbox.addWidget(self.Stack) self.setLayout(hbox) self.leftlist.currentRowChanged.connect(self.display) self.setGeometry(300, 50, 10, 10) self.setWindowTitle('StackedWidget demo') self.show() def stack1UI(self): layout = QFormLayout() layout.addRow("Name", QLineEdit()) layout.addRow("Address", QLineEdit()) # self.setTabText(0,"Contact Details") self.stack1.setLayout(layout) def stack2UI(self): layout = QFormLayout() sex = QHBoxLayout() sex.addWidget(QRadioButton("Male")) sex.addWidget(QRadioButton("Female")) layout.addRow(QLabel("Sex"), sex) layout.addRow("Date of Birth", QLineEdit()) self.stack2.setLayout(layout) def stack3UI(self): layout = QHBoxLayout() layout.addWidget(QLabel("subjects")) layout.addWidget(QCheckBox("Physics")) layout.addWidget(QCheckBox("Maths")) self.stack3.setLayout(layout) def state_changed(self): pass def display(self, i): self.Stack.setCurrentIndex(i) def main(): app = QApplication(sys.argv) ex = stackedExample() sys.exit(app.exec_()) if __name__ == '__main__': main()
Now I want to collect data from all of them and process it later. How can I know which checkbox was checked, for example? This code layout.addWidget(QCheckBox(“Physics”).stateChanged.connect(self.state_changed))
gives me
Process finished with exit code -1073741819 (0xC0000005)
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Answer
When you write
layout.addWidget(QCheckBox("Physics").stateChanged.connect(self.state_changed))
that doesn’t lookup the Physics checkbox but it creates a new checkbox. Because you don’t keep a Python reference to it, it will be destructed after you leave the constructor. However, it is still connected to a signal, which leads to unpredictable behavior.
If you want to connect to the original checkbox you will need to make a reference to it. Like so:
import sys from PyQt4.QtCore import * from PyQt4.QtGui import * class stackedExample(QWidget): def __init__(self): super(stackedExample, self).__init__() self.leftlist = QListWidget() self.leftlist.insertItem(0, 'Contact') self.leftlist.insertItem(1, 'Personal') self.leftlist.insertItem(2, 'Educational') self.stack1 = QWidget() self.stack2 = QWidget() self.stack3 = QWidget() self.stack1UI() self.stack2UI() self.stack3UI() # Renamed self.stack to self.stack since the convention is to start # class names with a capital but regular variables with a lower case. self.stack = QStackedWidget(self) self.stack.addWidget(self.stack1) self.stack.addWidget(self.stack2) self.stack.addWidget(self.stack3) hbox = QHBoxLayout(self) hbox.addWidget(self.leftlist) hbox.addWidget(self.stack) self.setLayout(hbox) self.leftlist.currentRowChanged.connect(self.display) self.setGeometry(300, 50, 10, 10) self.setWindowTitle('StackedWidget demo') self.show() def stack1UI(self): layout = QFormLayout() layout.addRow("Name", QLineEdit()) layout.addRow("Address", QLineEdit()) # self.setTabText(0,"Contact Details") self.stack1.setLayout(layout) def stack2UI(self): layout = QFormLayout() sex = QHBoxLayout() sex.addWidget(QRadioButton("Male")) sex.addWidget(QRadioButton("Female")) layout.addRow(QLabel("Sex"), sex) layout.addRow("Date of Birth", QLineEdit()) self.stack2.setLayout(layout) def stack3UI(self): layout = QHBoxLayout() layout.addWidget(QLabel("subjects")) self.physicsCheckBox = QCheckBox("Physics") layout.addWidget(self.physicsCheckBox) self.physicsCheckBox.stateChanged.connect(self.physicsCheckBoxStateChanged) layout.addWidget(QCheckBox("Maths")) self.stack3.setLayout(layout) def physicsCheckBoxStateChanged(self, state): isChecked = bool(state) # Convert from Qt.CheckState print("physicsCheckBox: {}".format(isChecked)) def display(self, i): self.stack.setCurrentIndex(i) def main(): app = QApplication(sys.argv) ex = stackedExample() sys.exit(app.exec_()) if __name__ == '__main__': main()
P.S. I renamed self.Stack
to self.stack
. It is a Python convention to let class definitions start with upper case characters and regular variables and function with lower case.