python - 在QMainWindow中放置一个小部件，如何定位而不是setCentralWidget

Question

我正在使用 QGridLayout，并通过使用 setCentralWidget 函数，行和列 (0,0) 从窗口的中心开始，从而留下大量空白空间。

如何让它居中，但从窗口顶部开始而不是从中间开始？

我对 Qt 还很陌生，想知道我的处理方式是否错误？我应该为 QWidget 创建一个新类吗？

class App(QMainWindow):
    def __init__(self):
        super().__init__()
        self.title = 'Data visualizing'
        self.left = 50
        self.top = 50
        self.width = 300
        self.height = 100
        self.initUI()

    def initUI(self):
        self.central_widget = QWidget()
        self.setCentralWidget(self.central_widget)

        # Create textbox
        self.textbox = QLineEdit(self)
        self.textbox.setReadOnly(True)

        # Create textbox 2
        self.textbox2 = QLineEdit(self)
        self.textbox2.setReadOnly(True)

        # Create button
        self.button = QPushButton('Load file 1', self)
        self.button.setToolTip('Click here to browse for the first data file')
        self.button.clicked.connect(self.on_click)

        # Create button 2
        self.button2 = QPushButton('Load file 2', self)
        self.button2.setToolTip('Click here to browse for the first data file')
        self.button2.clicked.connect(self.on_click)

        grid = QGridLayout()

        grid.addWidget(self.textbox, 0, 0, 0, 3)
        grid.addWidget(self.textbox2, 0, 3, 0, 3)
        grid.addWidget(self.button, 1, 1, 1, 1)
        grid.addWidget(self.button2, 1, 4, 1, 1)

        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.centralWidget().setLayout(grid)
        self.show()

    def openFileNameDialog(self):
        options = QFileDialog.Options()
        options |= QFileDialog.DontUseNativeDialog
        fileName, _ = QFileDialog.getOpenFileName(self, "QFileDialog.getOpenFileName()", "",
                                                  "All Files (*);;Comma seperated files (*.csv)", options=options)
        if fileName:
            self.textbox.setText(fileName)
            print(fileName)

    @pyqtSlot()
    def on_click(self):
        self.openFileNameDialog()
        print('PyQt5 button click')

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Answer 1

您必须在第 2 行中建立一个 Stretch，但在此之前您必须更正以下位置的 rowSpan:

grid.addWidget(self.textbox, 0, 0, 0, 3)
grid.addWidget(self.textbox2, 0, 3, 0, 3)

为了理解，让我们回顾一下 the docs :

void QGridLayout::addWidget(QWidget *widget, int fromRow, int fromColumn, int rowSpan, int columnSpan, Qt::Alignment alignment = ...)

This is an overloaded function.

This version adds the given widget to the cell grid, spanning multiple rows/columns. The cell will start at fromRow, fromColumn spanning rowSpan rows and columnSpan columns. The widget will have the given alignment.

If rowSpan and/or columnSpan is -1, then the widget will extend to the bottom and/or right edge, respectively.

也就是说，rowSpan 指示小部件将占用多少行，但您将其指示为 0，因此大小将不再由布局处理，而仅由位置处理，您必须将其更改为 1。

import sys
from PyQt5 import QtCore, QtGui, QtWidgets


class App(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        self.title = 'Data visualizing'
        self.left, self.top, self.width, self.height = 50, 50, 300, 100
        self.initUI()

    def initUI(self):
        self.central_widget = QtWidgets.QWidget()
        self.setCentralWidget(self.central_widget)

        # Create textboxs
        self.textbox = QtWidgets.QLineEdit(readOnly=True)
        self.textbox2 = QtWidgets.QLineEdit(readOnly=True)

        # Create buttons
        self.button = QtWidgets.QPushButton('Load file 1', 
            toolTip = 'Click here to browse for the first data file')
        self.button.clicked.connect(self.on_click)
        self.button2 = QtWidgets.QPushButton('Load file 2',
            toolTip = 'Click here to browse for the first data file')
        self.button2.clicked.connect(self.on_click)

        grid = QtWidgets.QGridLayout(self.centralWidget())

        grid.addWidget(self.textbox, 0, 0, 1, 3)
        grid.addWidget(self.textbox2, 0, 3, 1, 3)
        grid.addWidget(self.button, 1, 1, 1, 1)
        grid.addWidget(self.button2, 1, 4, 1, 1)
        grid.setRowStretch(2, 1)

        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.show()

    def openFileNameDialog(self):
        options = QtWidgets.QFileDialog.Options()
        options |= QtWidgets.QFileDialog.DontUseNativeDialog
        fileName, _ = QtWidgets.QFileDialog.getOpenFileName(self, "QFileDialog.getOpenFileName()", "",
                                                  "All Files (*);;Comma seperated files (*.csv)", options=options)
        if fileName:
            self.textbox.setText(fileName)
            print(fileName)

    @QtCore.pyqtSlot()
    def on_click(self):
        self.openFileNameDialog()
        print('PyQt5 button click')

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    ex = App()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()