pyqt5：qgridlayout将所有小部件放在左上角

Question

我正在使用pyqt5.qtwidgets.qgridlayout进行网格布局：

self.grid.addWidget(self.combo,0,0,1,2)            self.grid.addWidget(self.label_A,1,0)           self.grid.addWidget(self.input_A, 1, 1)            self.grid.addWidget(self.label_freq, 2, 0)            self.grid.addWidget(self.input_freq, 2, 1)            self.grid.addWidget(self.label_phase, 3, 0)            self.grid.addWidget(self.input_phase, 3, 1)

它无法正常工作，当我使用它进行调试时：

            for i in range(self.grid.count()):
                print(self.grid.itemAt(i).geometry())

返回：

PyQt5.QtCore.QRect(0, 0, 100, 42)
PyQt5.QtCore.QRect(0, 0, 640, 480)
PyQt5.QtCore.QRect(0, 0, 640, 480)
PyQt5.QtCore.QRect(0, 0, 640, 480)
PyQt5.QtCore.QRect(0, 0, 640, 480)
PyQt5.QtCore.QRect(0, 0, 640, 480)
PyQt5.QtCore.QRect(0, 0, 640, 480)

qgridlayout将所有小部件都放在顶部的角落。我应该怎么办？

我的PYQT5版本是5.15.6。 感谢您的建议。 原始代码如下：

class SubWindow(PyQt5.QtWidgets.QWidget):
    def __init__(self):
        super().__init__()

        self.setWindowTitle('sub')

        self.prop=dict[str,float]()
        self.prop = {'sig_type': 'sin',
                     'A': 1,
                     'freq': 1,
                     'phase': 0}

        combo=PyQt5.QtWidgets.QComboBox()
        combo.addItems(['sin','tri','rect','imp','step','exp'])
        combo.currentIndexChanged.connect(self.update)
        combo.currentIndexChanged.connect(lambda :print(combo.currentIndex()))
        combo.adjustSize()
        self.combo=combo

        ax=MplCanvas(self)
        self.ax=ax

        self.grid:PyQt5.QtWidgets.QGridLayout = PyQt5.QtWidgets.QGridLayout()
        self.grid.addWidget(self.combo,0,0)
        self.setLayout(self.grid)

        self.update()

    def show(self) -> None:
        super(SubWindow, self).show()
        self.update()

    def update(self) -> None:
        self.grid:PyQt5.QtWidgets.QGridLayout=PyQt5.QtWidgets.QGridLayout()

        if self.combo.currentIndex()==0:
            A=self.prop['A']
            freq=self.prop['freq']
            phase=self.prop['phase']
            x=np.linspace(0,2*np.pi,100)
            self.ax.axes.plot(x,np.sin(x))

            self.grid.addWidget(self.combo,0,0,1,2)

            self.label_A=PyQt5.QtWidgets.QLabel('A')
            self.input_A=PyQt5.QtWidgets.QLineEdit()
            self.input_A.editingFinished.connect(self.update)
            self.input_A.editingFinished.connect(lambda s:self.prop.__setitem__('A',float(s)))

            self.label_freq = PyQt5.QtWidgets.QLabel('freq')
            self.input_freq = PyQt5.QtWidgets.QLineEdit('freq')
            self.input_freq.editingFinished.connect(self.update)
            self.input_A.textEdited.connect(lambda s: self.prop.__setitem__('freq', float(s)))

            self.label_phase = PyQt5.QtWidgets.QLabel('phase')
            self.input_phase = PyQt5.QtWidgets.QLineEdit('phase')
            self.input_phase.editingFinished.connect(self.update)
            self.input_A.editingFinished.connect(lambda s: self.prop.__setitem__('phase', float(s)))

            self.grid.addWidget(self.label_A,1,0)
            self.grid.addWidget(self.input_A, 1, 1)
            self.grid.addWidget(self.label_freq, 2, 0)
            self.grid.addWidget(self.input_freq, 2, 1)
            self.grid.addWidget(self.label_phase, 3, 0)
            self.grid.addWidget(self.input_phase, 3, 1)

            for i in range(self.grid.count()):
                print(self.grid.itemAt(i).geometry())