python - 带有 QSizePolicy.Expanding 的 setSizePolicy() 不起作用 : the child does not expand to the size of the parent

Question

根据 http://doc.qt.io/qt-5/qsizepolicy.html#Policy-enum ，设置小部件的大小策略具有以下效果:

The sizeHint() is a sensible size, but the widget can be shrunk and still be useful. The widget can make use of extra space, so it should get as much space as possible (e.g. the horizontal direction of a horizontal slider).

因此，我希望下面的黄色小部件填满绿色小部件，但并没有发生。我做错了什么？

import sys

from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *

class Yellow(QWidget):

    def __init__(self, *args):
        super().__init__(*args)

        # Set palette
        bg = QPalette()
        bg.setColor(QPalette.Window, Qt.yellow)
        self.setAutoFillBackground(True)
        self.setPalette(bg)

        self.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)

class Green(QWidget):

    def __init__(self, *args):
        super().__init__(*args)

        # Set palette
        bg = QPalette()
        bg.setColor(QPalette.Window, Qt.green)
        self.setAutoFillBackground(True)
        self.setPalette(bg)

        self.yellow = Yellow(self)

class App(QMainWindow):

    def __init__(self):
        super().__init__()
        self.title = 'PyQt5'
        self.left = 10
        self.top = 10
        self.width = 200
        self.height = 200 
        self.initUI()

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

        self.green = Green(self)
        self.green.resize(184, 154)
        self.green.move(10, 10)

        self.show()

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

    ex = App()
    sys.exit(app.exec_())

Answer 1

使用布局:

class Green(QWidget):

    def __init__(self, *args):
        super().__init__(*args)

        # Set palette
        bg = QPalette()
        bg.setColor(QPalette.Window, Qt.green)
        self.setAutoFillBackground(True)
        self.setPalette(bg)

        self.yellow = Yellow(self)
        self.myLayout = QGridLayout()
        self.myLayout.addWidget(self.yellow)
        self.setLayout(self.myLayout)

结果:

如果添加 self.myLayout.setContentsMargins(0,0,0,0) 黄色小部件完全覆盖绿色小部件: