为 size 属性设置动画时从中心调整小部件的大小

Question

我正在尝试编写一个小部件，它在鼠标悬停时会略微增大，而在鼠标再次离开时会减小。
到目前为止，这是我想出的：

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

from random import randrange


class MainWindow(QMainWindow):

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

        self.setFixedSize(500, 500)

        cent_widget = QWidget()
        self.setCentralWidget(cent_widget)

        layout = QVBoxLayout()
        cent_widget.setLayout(layout)

        layout.addWidget(MyItem(), Qt.AlignCenter,
                         alignment=Qt.AlignCenter)


class MyItem(QLabel):

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

        self.setBaseSize(200, 250)
        self.setMinimumSize(self.baseSize())
        self.resize(self.baseSize())

        self.setSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed)

        self.setStyleSheet('background: #{:02x}{:02x}{:02x}'.format(
            randrange(255), randrange(255), randrange(255)
        ))

        # Animation
        self._enlarged = False
        self.zoom_factor = 1.2

        self.anim = QPropertyAnimation(self, b'size')
        self.anim.setEasingCurve(QEasingCurve.InOutSine)
        self.anim.setDuration(250)

    def enterEvent(self, event: QEvent) -> None:
        self.resize_anim()
        self._enlarged = True

    def leaveEvent(self, event: QEvent) -> None:
        self.resize_anim()
        self._enlarged = False

    def resize_anim(self):
        if self._enlarged:
            new_size = self.baseSize()
        else:
            new_size = QSize(
                int(self.baseSize().width() * self.zoom_factor),
                int(self.baseSize().height() * self.zoom_factor)
            )
        self.anim.setEndValue(new_size)
        self.anim.start()


if __name__ == '__main__':
    app = QApplication([])
    window = MainWindow()
    window.show()
    app.exec()

它几乎按照我想要的方式工作，我唯一的问题是小部件从左上角而不是中心调整大小。
我该如何改变呢？

Answer 1

您应该使用几何属性而不是使用 size 属性设置动画，因为它是相对于父窗口小部件的，因此您可以为其几何设置动画，使中心保持不变。

from PyQt5.QtCore import (
    QAbstractAnimation,
    QEasingCurve,
    QEvent,
    QPropertyAnimation,
    QRect,
    Qt,
)
from PyQt5.QtGui import QColor
from PyQt5.QtWidgets import (
    QApplication,
    QLabel,
    QMainWindow,
    QSizePolicy,
    QVBoxLayout,
    QWidget,
)

import random


class MainWindow(QMainWindow):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.setFixedSize(500, 500)

        cent_widget = QWidget()
        self.setCentralWidget(cent_widget)

        layout = QVBoxLayout(cent_widget)
        layout.addWidget(MyItem(), alignment=Qt.AlignCenter)


class MyItem(QLabel):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.setBaseSize(200, 250)
        self.setMinimumSize(self.baseSize())
        self.resize(self.baseSize())

        self.setSizePolicy(QSizePolicy.Fixed, QSizePolicy.Fixed)

        self.setStyleSheet(
            "background: {}".format(QColor(*random.sample(range(255), 3)).name())
        )

        # Animation
        self.zoom_factor = 1.2

        self.anim = QPropertyAnimation(self, b"geometry")
        self.anim.setEasingCurve(QEasingCurve.InOutSine)
        self.anim.setDuration(250)

    def enterEvent(self, event: QEvent) -> None:

        initial_rect = self.geometry()
        final_rect = QRect(
            0,
            0,
            int(initial_rect.width() * self.zoom_factor),
            int(initial_rect.height() * self.zoom_factor),
        )
        final_rect.moveCenter(initial_rect.center())

        self.anim.setStartValue(initial_rect)
        self.anim.setEndValue(final_rect)
        self.anim.setDirection(QAbstractAnimation.Forward)
        self.anim.start()

    def leaveEvent(self, event: QEvent) -> None:
        self.anim.setDirection(QAbstractAnimation.Backward)
        self.anim.start()


if __name__ == "__main__":
    app = QApplication([])
    window = MainWindow()
    window.show()
    app.exec()