窗口尺寸变化时，如何结合Paint Event适配Widget的动画路径

Hey there! Let's work through those two problems you're facing with your path animation widget. I'll break down the fixes step by step:

Problem 1: Animation sticks to old path when window resizes #

Your original code creates the path with fixed 400x400 coordinates and initializes the animation only once on double-click. Even though the path updates in paintEvent when the window resizes, the running animation never picks up this new path.

Problem 2: Widget doesn't adapt to window size changes #

The painter.setWindow(0, 0, 400, 400) line locks the painter's coordinate system to a fixed size, so both the drawn path and the button's position won't scale with the window.

Modified Code with Complete Fixes #

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

class PathAnimation(QPropertyAnimation):
    def __init__(self, path=QPainterPath(), object=None, property=None):
        super().__init__(object, property)
        self.path = path

    def updateCurrentTime(self, currentTime):
        easedProgress = self.easingCurve().valueForProgress(currentTime / self.duration())
        pt = self.path.pointAtPercent(easedProgress)
        self.updateCurrentValue(pt)
        self.valueChanged.emit(pt)

    # Add a method to update the animation's path dynamically
    def setPath(self, path):
        self.path = path

class DemoB(QWidget):
    def __init__(self):
        super().__init__()
        self.resize(400, 400)
        self.button = QPushButton('test', self)
        self.ani = None
        # Initialize path with current window size
        self.updatePath()

    def updatePath(self):
        # Generate path using the widget's actual current dimensions
        self.path = QPainterPath()
        self.path.moveTo(0, 0)  # Start at top-left corner
        # Use widget width/height for curve control points
        self.path.cubicTo(
            QPointF(0, self.height()),
            QPointF(self.width() / 2, 0),
            QPointF(self.width(), self.height())
        )

    def resizeEvent(self, event):
        super().resizeEvent(event)
        # Refresh path whenever window is resized
        self.updatePath()
        # If animation is running, update its path immediately
        if self.ani and self.ani.state() == QAbstractAnimation.Running:
            self.ani.setPath(self.path)
        # Trigger repaint to show the updated path
        self.update()

    def mouseDoubleClickEvent(self, e):
        # Restart animation with the latest path
        if self.ani:
            self.ani.stop()
        self.ani = PathAnimation(self.path, self.button, b'pos')
        self.ani.setDuration(2000)
        self.ani.start()

    def paintEvent(self, e):
        painter = QPainter(self)
        # Remove fixed coordinate lock - use widget's native system
        painter.drawPath(self.path)

app = QApplication([])
demo = DemoB()
demo.show()
app.exec()

Key Changes Explained #

• Dynamic Path Generation: The new updatePath() method creates the cubic curve using the widget's current width() and height() instead of hardcoded values. This ensures the path always matches the window size.
• Resize Event Handling: Overriding resizeEvent() lets us update the path the moment the window changes size. If the animation is running, we immediately update its path so the button follows the new curve.
• Fixed Coordinate Lock Removed: By deleting painter.setWindow(0, 0, 400, 400), the painter uses the widget's actual coordinate system, making both the path and button position scale with the window.
• Animation Management: We track the animation instance to either update its path mid-run or recreate it with the latest path when double-clicking again.

内容的提问来源于stack exchange，提问作者jett chen