下面的给定代码显示带有4 QMainWindow
的QGraphicsView
,用鼠标在其中绘制。它可以按预期工作,但是关闭它时,控制台中会出现以下错误消息:
Process finished with exit code 139 (interrupted by signal 11: SIGSEGV)
代码有什么问题?
import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QGraphicsView, QGraphicsScene, QGraphicsPathItem
from PyQt5.QtGui import QPainterPath, QPen
from PyQt5.QtCore import Qt
from PyQt5.uic import loadUi
# Based on code from https://stackoverflow.com/a/44248794/7481773
class MainWindow(QMainWindow):
def __init__(self):
super().__init__()
loadUi("mainwindow.ui", self)
self.verticalLayout_top_left.addWidget(GraphicsView())
self.verticalLayout_top_right.addWidget(GraphicsView())
self.verticalLayout_bottom_left.addWidget(GraphicsView())
self.verticalLayout_bottom_right.addWidget(GraphicsView())
class GraphicsView(QGraphicsView):
def __init__(self):
super().__init__()
self.start = None
self.end = None
self.setScene(QGraphicsScene())
self.path = QPainterPath()
self.item = GraphicsPathItem()
self.scene().addItem(self.item)
self.contents_rect = self.contentsRect()
self.setSceneRect(0, 0, self.contents_rect.width(), self.contents_rect.height())
self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
def mousePressEvent(self, event):
self.start = self.mapToScene(event.pos())
self.path.moveTo(self.start)
def mouseMoveEvent(self, event):
self.end = self.mapToScene(event.pos())
self.path.lineTo(self.end)
self.start = self.end
self.item.setPath(self.path)
class GraphicsPathItem(QGraphicsPathItem):
def __init__(self):
super().__init__()
pen = QPen()
pen.setColor(Qt.black)
pen.setWidth(5)
self.setPen(pen)
def main():
app = QApplication(sys.argv)
main_window = MainWindow()
main_window.show()
app.exec_()
if __name__ == "__main__":
main()
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>800</width>
<height>600</height>
</rect>
</property>
<property name="windowTitle">
<string>MainWindow</string>
</property>
<widget class="QWidget" name="centralwidget">
<layout class="QGridLayout" name="gridLayout">
<item row="1" column="0">
<widget class="QPushButton" name="pushButton_left">
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
<item row="0" column="0">
<layout class="QVBoxLayout" name="verticalLayout_top_left"/>
</item>
<item row="0" column="1">
<layout class="QVBoxLayout" name="verticalLayout_top_right"/>
</item>
<item row="1" column="1">
<widget class="QPushButton" name="pushButton_right">
<property name="text">
<string>PushButton</string>
</property>
</widget>
</item>
<item row="2" column="0">
<layout class="QVBoxLayout" name="verticalLayout_bottom_left"/>
</item>
<item row="2" column="1">
<layout class="QVBoxLayout" name="verticalLayout_bottom_right"/>
</item>
</layout>
</widget>
<widget class="QMenuBar" name="menubar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>800</width>
<height>24</height>
</rect>
</property>
</widget>
<widget class="QStatusBar" name="statusbar"/>
</widget>
<resources/>
<connections/>
</ui>
之所以引起此问题,是因为即使您完成运行app.exec_(),该应用程序仍会释放需要访问QApplication实例的资源,但在您这种情况下,通过使Qt的内部功能删除“ app”访问未保留的内存。
考虑到上述情况,一种可能的解决方案是扩展“ app”的范围,以便在通过执行全局变量执行主要功能后不将其删除。
# ...
app = None
def main():
global app
app = QApplication(sys.argv)
# ...