PyQt5：如何将子小部件移动到主 window 中？

Question

This code opens 3 separate windows:

1) main window
2) widgetA 
3) widgetB.

How to write the code in such a way that it moves 2 and 3 into 1?

So we just have one main window and in it 2 widgets that can communicate with each other. Also, an additional feature: how can we write a function in such a way that it listens to incoming data and then sends it away?

class mainwindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(mainwindow, self).__init__(parent)

        self.button = QtWidgets.QPushButton("Click Me", self)
        self.button.clicked.connect(self.on_button_clicked)

        self.setCentralWidget(self.button)

        self.widgetA = widgetA()
        self.widgetB = widgetB()

        self.widgetA.procStart.connect(self.widgetB.on_procStart)
        self.widgetB.procDone.connect(self.widgetA.on_widgetB_procDone)

    @QtCore.pyqtSlot()
    def on_button_clicked(self):
        self.widgetA.show()
        self.widgetB.show()

        self.widgetA.raise_()

class widgetA(QtWidgets.QWidget):
    procStart = QtCore.pyqtSignal(str)

    def __init__(self, parent=None):
        super(widgetA, self).__init__(parent)

        self.lineEdit = QtWidgets.QLineEdit(self)
        self.lineEdit.setText("Hello!")

        self.button = QtWidgets.QPushButton("Send Message to B", self)
        self.button.clicked.connect(self.on_button_clicked)

        self.layout = QtWidgets.QHBoxLayout(self)
        self.layout.addWidget(self.lineEdit)
        self.layout.addWidget(self.button)

    @QtCore.pyqtSlot()
    def on_button_clicked(self):
        self.procStart.emit(self.lineEdit.text())

    @QtCore.pyqtSlot(str)
    def on_widgetB_procDone(self, message):
        self.lineEdit.setText("From B: " + message)

        self.raise_()


class widgetB(QtWidgets.QWidget):

    procDone = QtCore.pyqtSignal(str)

    def __init__(self, parent=None):
        super(widgetB, self).__init__(parent)

        self.lineEdit = QtWidgets.QLineEdit(self)
        self.button = QtWidgets.QPushButton("Send Message to A", self)
        self.layout = QtWidgets.QHBoxLayout(self)
        self.layout.addWidget(self.lineEdit)
        self.layout.addWidget(self.button)

        self.button.clicked.connect(self.on_button_clicked)

    @QtCore.pyqtSlot()
    def on_button_clicked(self):
        self.procDone.emit(self.lineEdit.text())

    @QtCore.pyqtSlot(str)
    def on_procStart(self, message):
        self.lineEdit.setText("From A: " + message)

        self.raise_()

if __name__ == "__main__":
    import sys

    app = QtWidgets.QApplication(sys.argv)
    main = mainwindow()
    main.show()
    sys.exit(app.exec_())

Answer 1

If you need to show more than one widget into a "top level window" (no matter if it's a QWidget, a QDialog or a QMainWindow) you need to create a container widget.

In your case you're using a QMainWindow, which is a very special kind of QWidget, as it has its own (internal and almost unaccessible) layout. The main content that is normally shown within a QMainWindow (besides its menubar, statusbar, toolbars and dockbars) is called the "central widget", and you're setting it to a QPushButton, so there's no room for anything else.

The most common and conventional approach is to create a new QWidget (which is an empty widget that is used as the basis for all Qt widgets), set a layout for it and add the actual widgets to it:

class mainwindow(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(mainwindow, self).__init__(parent)

        

        self.button = QtWidgets.QPushButton("Click Me", self)
        self.button.clicked.connect(self.on_button_clicked)

        self.widgetA = widgetA()
        self.widgetB = widgetB()

        
        # ...

Note that if you're not using QMainWindow but a standard QWidget or QDialog, you obviously don't need to use the "central widget", and you can just create a new layout on the current instance ( self ).

class SomeWidget(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        layout = QtWidgets.QVBoxLayout(self)
        # ...