python - 如何正确关闭 PyQt 的 QtApplication？

Question

我对 Qt 一无所知，但我试图厚颜无耻地从其他地方借用代码 (http://lateral.netmanagers.com.ar/weblog/posts/BB901.html#disqus_thread) . ;)

我有一个问题。当我第一次运行 test() 时，一切都很顺利。但是，当我第二次运行它时，出现了令人讨厌的段错误。我怀疑问题是我没有正确结束 qt 的东西。我应该对该程序进行哪些更改才能使其多次运行？提前致谢!

from PyQt4 import QtCore, QtGui, QtWebKit
import logging

logging.basicConfig(level=logging.DEBUG)

class Capturer(object):
    """A class to capture webpages as images"""

    def __init__(self, url, filename, app):
        self.url = url
        self.app = app
        self.filename = filename
        self.saw_initial_layout = False
        self.saw_document_complete = False

    def loadFinishedSlot(self):
        self.saw_document_complete = True
        if self.saw_initial_layout and self.saw_document_complete:
            self.doCapture()

    def initialLayoutSlot(self):
        self.saw_initial_layout = True
        if self.saw_initial_layout and self.saw_document_complete:
            self.doCapture()

    def capture(self):
        """Captures url as an image to the file specified"""
        self.wb = QtWebKit.QWebPage()
        self.wb.mainFrame().setScrollBarPolicy(
            QtCore.Qt.Horizontal, QtCore.Qt.ScrollBarAlwaysOff)
        self.wb.mainFrame().setScrollBarPolicy(
            QtCore.Qt.Vertical, QtCore.Qt.ScrollBarAlwaysOff)
        self.wb.loadFinished.connect(self.loadFinishedSlot)
        self.wb.mainFrame().initialLayoutCompleted.connect(
            self.initialLayoutSlot)
        logging.debug("Load %s", self.url)
        self.wb.mainFrame().load(QtCore.QUrl(self.url))

    def doCapture(self):
        logging.debug("Beginning capture")
        self.wb.setViewportSize(self.wb.mainFrame().contentsSize())
        img = QtGui.QImage(self.wb.viewportSize(), QtGui.QImage.Format_ARGB32)
        painter = QtGui.QPainter(img)
        self.wb.mainFrame().render(painter)
        painter.end()
        img.save(self.filename)
        self.app.quit()

def test():
    """Run a simple capture"""
    app = QtGui.QApplication([])
    c = Capturer("http://www.google.com", "google.png", app)
    c.capture()
    logging.debug("About to run exec_")
    app.exec_()

DEBUG:root:Load http://www.google.com
QObject::connect: Cannot connect (null)::configurationAdded(QNetworkConfiguration) to QNetworkConfigurationManager::configurationAdded(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::configurationRemoved(QNetworkConfiguration) to QNetworkConfigurationManager::configurationRemoved(QNetworkConfiguration)
QObject::connect: Cannot connect (null)::configurationUpdateComplete() to QNetworkConfigurationManager::updateCompleted()
QObject::connect: Cannot connect (null)::onlineStateChanged(bool) to QNetworkConfigurationManager::onlineStateChanged(bool)
QObject::connect: Cannot connect (null)::configurationChanged(QNetworkConfiguration) to QNetworkConfigurationManager::configurationChanged(QNetworkConfiguration)

Process Python segmentation fault (this last line is comes from emacs)

Answer 1

您需要在测试函数之外处理 QApplication，有点像单例(实际上在这里很合适)。

您可以做的是检查 QtCore.qApp 是否是某种东西(或者 QApplication.instance() 是否返回 None 或其他东西)，然后才创建您的 qApp，否则，使用全局的。

它不会在你的 test() 函数之后被销毁，因为 PyQt 将应用程序存储在某个地方。

如果你想确保它被正确处理，只需为它设置一个延迟初始化的单例。