使用 enterEvent 和 leaveEvent 时 PyQt QStackedWidget 上的递归错误

Question

我使用的是QStackedWidget，它有自己的enterEvent 和leaveEvent。当我将鼠标移动到QStackedWidget 时，enterEvent 将当前索引设置为1，在leaveEvent 上将当前索引设置为0，以便在鼠标进入和鼠标离开时显示不同的小部件在QStackedWidget 的区域内。只有当我快速将鼠标移入和移出时，它才会执行我想要的操作，如果我将鼠标放在我得到RecursionError: maximum recursion depth exceeded 的区域中太长。

这是因为小部件变化太快以至于内部堆栈跟不上吗？我的问题是“我如何确保不会发生此错误？我想显示一个小部件只要鼠标在QStackedWidget 上，当它不是时我想显示原始小部件。”

以下是我修改的代码（Original Source使用按钮设置索引，是PyQt4）

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

class FaderWidget(QWidget):

    def __init__(self, old_widget, new_widget):
        QWidget.__init__(self, new_widget)
        self.old_pixmap = QPixmap(new_widget.size())
        old_widget.render(self.old_pixmap)
        self.pixmap_opacity = 1.0
        self.timeline = QTimeLine()
        self.timeline.valueChanged.connect(self.animate)
        self.timeline.finished.connect(self.close)
        self.timeline.setDuration(333)
        self.timeline.start()

        self.resize(new_widget.size())
        self.show()


    def animate(self, value):

        self.pixmap_opacity = 1.0 - value
        self.repaint()

class StackedWidget(QStackedWidget):

    def __init__(self, parent = None):
        QStackedWidget.__init__(self, parent)

    def setCurrentIndex(self, index):
        self.fader_widget = FaderWidget(self.currentWidget(), self.widget(index))
        super().setCurrentIndex(index)

    def enterEvent(self,event):
        self.setCurrentIndex(1)

    def leaveEvent(self,event):
        self.setCurrentIndex(0)


if __name__ == "__main__":

    app = QApplication(sys.argv)

    window = QWidget()

    stack = StackedWidget()
    cal=QCalendarWidget()
    stack.addWidget(cal)
    editor = QTextEdit()
    editor.setPlainText("Hello world! "*100)
    stack.addWidget(editor)

    layout = QGridLayout(window)
    layout.addWidget(stack, 0, 0, 1, 2)

    window.show()
    sys.exit(app.exec_())

Answer 1

发生递归是因为当您启动 FaderWidget 时，它会更改焦点并再次调用 enterEvent，从而创建一个新的 FaderWidget。

解决方法是验证旧索引与新索引不同，才创建FadeWidget：

import sys

from PyQt5.QtCore import QTimeLine
from PyQt5.QtGui import QPainter, QPixmap
from PyQt5.QtWidgets import (
    QApplication,
    QCalendarWidget,
    QGridLayout,
    QStackedWidget,
    QTextEdit,
    QWidget,
)


class FaderWidget(QWidget):
    def __init__(self, old_widget, new_widget):
        QWidget.__init__(self, new_widget)
        self.pixmap_opacity = 1.0
        self.old_pixmap = QPixmap(new_widget.size())
        old_widget.render(self.old_pixmap)

        self.timeline = QTimeLine()
        self.timeline.valueChanged.connect(self.animate)
        self.timeline.finished.connect(self.close)
        self.timeline.setDuration(333)
        self.timeline.start()

        self.resize(new_widget.size())
        self.show()

    def paintEvent(self, event):
        painter = QPainter(self)
        painter.setOpacity(self.pixmap_opacity)
        painter.drawPixmap(0, 0, self.old_pixmap)

    def animate(self, value):
        self.pixmap_opacity = 1.0 - value
        self.update()


class StackedWidget(QStackedWidget):
    def setCurrentIndex(self, index):
        if self.currentIndex() != index:
            self.fader_widget = FaderWidget(self.currentWidget(), self.widget(index))
        super().setCurrentIndex(index)

    def enterEvent(self, event):
        self.setCurrentIndex(1)

    def leaveEvent(self, event):
        self.setCurrentIndex(0)


if __name__ == "__main__":

    app = QApplication(sys.argv)

    window = QWidget()

    stack = StackedWidget()
    cal = QCalendarWidget()
    stack.addWidget(cal)
    editor = QTextEdit()
    editor.setPlainText("Hello world! " * 100)
    stack.addWidget(editor)

    layout = QGridLayout(window)
    layout.addWidget(stack, 0, 0, 1, 2)

    window.show()
    sys.exit(app.exec_())