Why my QToolButton which I try to make collapsible doesn't collapse properly?

Question

guys.

Asking for your help to troubleshoot my test script. I am practicing to make collapsible button with widgets inside.

Script was mainly taken from another question in stackoverflow about collapsible buttons.

So I am trying to put under QTabWidget my class CollpsibleBox(QWidget). Problem is that my CollapsibleBox is acting very weird - buttons are jumping , sometimes it doesn't open/close properly.

I was wondering if it's some mistake in placing correctly my widget under QTabWidget or is there some problem with animation?

import random
from PySide2.QtGui import QPixmap, QBrush, QColor, QIcon, QPainterPath, QPolygonF, QPen, QTransform
from PySide2.QtCore import QSize, Qt, Signal, QPointF, QRect, QPoint, QParallelAnimationGroup, QPropertyAnimation, QAbstractAnimation
from PySide2.QtWidgets import QMainWindow, QDialog, QVBoxLayout, QHBoxLayout, QGraphicsView, QGraphicsScene, QFrame, \
    QSizePolicy, QGraphicsPixmapItem, QApplication, QRubberBand, QMenu, QMenuBar, QTabWidget, QWidget, QPushButton, \
    QSlider, QGraphicsPolygonItem, QToolButton, QScrollArea, QLabel

extraDict = {'buttonSetA': ['test'], 'buttonSetB': ['test']}
tabList = ['Main', 'Extra']
_ui = dict()

class MainWindow(QDialog):
    def __init__(self, parent=None):
        QDialog.__init__(self, parent=parent)
        self.create()

    def create(self, **kwargs):
        _ui['mainLayout'] = QVBoxLayout()
        _ui['tabWidget'] = QTabWidget()
        _ui['mainLayout'].addWidget(_ui['tabWidget'])
        for tab in tabList:
            _ui['tab' + tab] = QWidget()
            _ui['tabWidget'].addTab(_ui['tab' + tab], tab)

        _ui['tabExtra'].layout = QVBoxLayout()
        _ui['tabExtra'].setLayout(_ui['tabExtra'].layout)

        _ui['content'] = QWidget()
        _ui['tabExtra'].layout.addWidget(_ui['content'])

        vlay = QVBoxLayout(_ui['content'])
        for name in extraDict.keys():
            box = CollapsibleBox(name)
            vlay.addWidget(box)
            lay = QVBoxLayout()
            for j in range(8):
                label = QLabel("{}".format(j))
                color = QColor(*[random.randint(0, 255) for _ in range(3)])
                label.setStyleSheet(
                    "background-color: {}; color : white;".format(color.name())
                )
                label.setAlignment(Qt.AlignCenter)
                lay.addWidget(label)

            box.setContentLayout(lay)
        self.setLayout(_ui['mainLayout'])

class CollapsibleBox(QWidget):
    def __init__(self, name):
        super(CollapsibleBox, self).__init__()
        self.toggle_button = QToolButton(text=name, checkable=True, checked=False)
        self.toggle_button.setToolButtonStyle(Qt.ToolButtonTextBesideIcon)
        self.toggle_button.setArrowType(Qt.RightArrow)
        self.toggle_button.pressed.connect(self.on_pressed)
        self.toggle_animation = QParallelAnimationGroup(self)
        self.content_area = QScrollArea(maximumHeight=0, minimumHeight=0)
        self.content_area.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Fixed)
        self.content_area.setFrameShape(QFrame.NoFrame)

        lay = QVBoxLayout(self)
        lay.setSpacing(0)
        lay.setContentsMargins(0, 0, 0, 0)
        lay.addWidget(self.toggle_button)
        lay.addWidget(self.content_area)

        self.toggle_animation.addAnimation(QPropertyAnimation(self, b"minimumHeight"))
        self.toggle_animation.addAnimation(QPropertyAnimation(self, b"maximumHeight"))
        self.toggle_animation.addAnimation(QPropertyAnimation(self.content_area, b"maximumHeight"))

    def on_pressed(self):
        checked = self.toggle_button.isChecked()
        self.toggle_button.setArrowType(Qt.DownArrow if not checked else Qt.RightArrow)
        self.toggle_animation.setDirection(QAbstractAnimation.Forward
            if not checked
            else QAbstractAnimation.Backward
                                           )
        self.toggle_animation.start()

    def setContentLayout(self, layout):
        lay = self.content_area.layout()
        del lay
        self.content_area.setLayout(layout)
        collapsed_height = (self.sizeHint().height() - self.content_area.maximumHeight())
        content_height = layout.sizeHint().height()
        for i in range(self.toggle_animation.animationCount()):
            animation = self.toggle_animation.animationAt(i)
            animation.setDuration(500)
            animation.setStartValue(collapsed_height)
            animation.setEndValue(collapsed_height + content_height)
        content_animation = self.toggle_animation.animationAt(self.toggle_animation.animationCount() - 1)
        content_animation.setDuration(500)
        content_animation.setStartValue(0)
        content_animation.setEndValue(content_height)

if __name__ == '__main__':
    import sys
    app = QApplication(sys.argv)
    window = MainWindow()
    window.setGeometry(500, 100, 500, 500)
    window.show()
    sys.exit(app.exec_())

Answer 1

The problem is that you are only adding two widgets to the full layout, and the layout will try to place them as better as possible (tipically at the center of the area that is available for each widget, based on its size hints).

You could either set the alignment of the widget for the layout (placing the buttons on top of their available space):

        vlay = QVBoxLayout(_ui['content'])
        for name in extraDict.keys():
            box = CollapsibleBox(name)
            vlay.addWidget(box, alignment=Qt.AlignTop)

Or add a stretch to the bottom of the layout:

        vlay = QVBoxLayout(_ui['content'])
        for name in extraDict.keys():
            # ...
        vlay.addStretch(1)

which will position all buttons on top of the layout.

As a side note, I'd suggest you to avoid the dictionary logic for the ui, as it might become very confusing and prone to errors. If you really need to do that for some (I hope, very good) reason that's ok, but please avoid it when asking questions: it makes really hard to read your code, and people might end up just ignoring your question at all.