QMainWindow 布局错误？

Question

我在 PyQT5 中得到了错误的布局。我究竟做错了什么？是否有一些预定义的小字段大小或类似的？我将 main window 创建为 QMainWindow 并在其中创建了一个小部件作为中央小部件。这是它的样子：

class Main(QWidget):
    """The main widget with label and LineEdit"""
    def __init__(self, parent=None):
        super().__init__(parent)
        self.initUi()

    def initUi(self):
        """Initialize the UI of the main widget"""
        self.mySourceLabel = QLabel("Select your file:")
        self.mySourceLine = QLineEdit()
        self.mySourceLine.setPlaceholderText("File name here")

        # Set layout
        grid = QGridLayout()
        #grid.setSpacing(5)
        grid.addWidget(self.mySourceLabel, 0, 0)
        grid.addWidget(self.mySourceLine, 1, 0)
        self.setLayout(grid)

class MyApp(QMainWindow):
    """Main application class"""
    def __init__(self, parent=None):
        super().__init__(parent)
        self.initUi()

    def initUi(self):
        """Initialize UI of an application"""
        # main window size, title
        self.setGeometry(400, 300, 400, 300)
        self.setWindowTitle("Version upgrade ")

        # create instance of a class Main
        self.main = Main(self)

        # create central widget, create grid layout
        centralWidget = QWidget()
        centralLayout = QGridLayout()
        centralWidget.setLayout(centralLayout)

Answer 1

当您将父级传递给 QWidget 时，这将定位相对于其父级的位置并生成与您获得的小部件一样的小部件，为了解决这个问题，使用了布局，QMainWindow 是一个特殊的 QWidget，因为它已经预定义元素，所以它已经有一个布局：

在 QMainWindow 中，必须使用 setCentralWidget 函数将小部件添加到 centralwidget，在您的情况下：

class MyApp(QMainWindow):
    """Main application class"""
    def __init__(self, parent=None):
        super().__init__(parent)
        self.initUi()

    def initUi(self):
        [...]
        centralWidget = Main(self)
        self.setCentralWidget(centralWidget)

完整代码：

class Main(QWidget):
    """The main widget with label and LineEdit"""
    def __init__(self, parent=None):
        super().__init__(parent)
        self.initUi()

    def initUi(self):
        """Initialize the UI of the main widget"""
        self.mySourceLabel = QLabel("Select your file:")
        self.mySourceLine = QLineEdit()
        self.mySourceLine.setPlaceholderText("File name here")

        # Set layout
        grid = QGridLayout()
        #grid.setSpacing(5)
        grid.addWidget(self.mySourceLabel, 0, 0)
        grid.addWidget(self.mySourceLine, 1, 0)
        self.setLayout(grid)

class MyApp(QMainWindow):
    """Main application class"""
    def __init__(self, parent=None):
        super().__init__(parent)
        self.initUi()

    def initUi(self):
        """Initialize UI of an application"""
        # main window size, title
        self.setGeometry(400, 300, 400, 300)
        self.setWindowTitle("Version upgrade ")

        # create central widget, create grid layout
        centralWidget = Main(self)
        self.setCentralWidget(centralWidget)

截图：

QMainWindow 布局错误？

Wrong layout in QMainWindow?

python

pyqt

qmainwindow

pyqt5