在PyQt的网格布局中使带有QPainter的小部件可滚动

import sys
from PyQt5.QtWidgets import QApplication, QWidget, QScrollArea, QVBoxLayout
from PyQt5.QtGui import QPainter, QColor, QPen
from PyQt5.QtCore import Qt

class CustomWidget(QWidget):
    def paintEvent(self, event):
        painter = QPainter(self)
        painter.setRenderHint(QPainter.Antialiasing)
        pen = QPen(Qt.black, 2)
        painter.setPen(pen)
        painter.setBrush(QColor(255, 0, 0))
        painter.drawRect(0, 0, 100, 100)

if __name__ == '__main__':
    app = QApplication(sys.argv)

    scroll_area = QScrollArea()
    widget = QWidget()
    layout = QVBoxLayout(widget)
    scroll_area.setWidgetResizable(True)
    scroll_area.setWidget(widget)

    for i in range(10):
        custom_widget = CustomWidget()
        layout.addWidget(custom_widget)

    scroll_area.show()

    sys.exit(app.exec_())