code like the following .After it running for about half a minute ,then close the window, then the "Python has stopped working" dialog pops up(you had better try more than once. )
I wonder why this happen ?any solution to this ?
Tested on Windows with PyQt4-4.11.3-gpl-Py3.4-Qt4.8.6-x32.exe
from PyQt4.QtCore import *
from PyQt4.QtGui import *
class MainWindow(QMainWindow):
def __init__(self):
super().__init__()
self.setWindowIcon(QIcon("./wa.png"))
self.createTrayIcon()
def createTrayIcon(self):
self.trayIcon = QSystemTrayIcon()
self.trayIcon.setIcon(self.windowIcon())
self.trayIcon.show()
if __name__ == "__main__":
import sys
app = QApplication(sys.argv)
ui = MainWindow()
ui.show()
sys.exit(app.exec_())
I do my PyQt work on linux, so there might be differences, but usually I construct my MainWindow with the following call:
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
...
I can run your code in python3, but after I exit I get the Segmentation Fault. If I change the constructor to what I indicated above the Fault is not reproduced.
Hope this helps
Related
I have got this problem. I´m trying to set text on a lineEdit object on pyqt4, then wait for a few seconds and changing the text of the same lineEdit. For this I´m using the time.sleep() function given on the python Time module. But my problem is that instead of setting the text, then waiting and finally rewrite the text on the lineEdit, it just waits the time it´s supposed to sleep and only shows the final text. My code is as follows:
from PyQt4 import QtGui
from gui import *
class Ventana(QtGui.QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
QtGui.QWidget.__init__(self, parent)
self.setupUi(self)
self.button.clicked.connect(self.testSleep)
def testSleep(self):
import time
self.lineEdit.setText('Start')
time.sleep(2)
self.lineEdit.setText('Stop')
def mainLoop(self, app ):
sys.exit( app.exec_())
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Ventana()
window.show()
sys.exit(app.exec_())
You can't use time.sleep here because that freezes the GUI thread, so the GUI will be completely frozen during this time.
You should probably use a QTimer and use it's timeout signal to schedule a signal for deferred delivery, or it's singleShot method.
For example (adapted your code to make it run without dependencies):
from PyQt4 import QtGui, QtCore
class Ventana(QtGui.QWidget):
def __init__(self, parent=None):
QtGui.QWidget.__init__(self, parent)
self.setLayout(QtGui.QVBoxLayout())
self.lineEdit = QtGui.QLineEdit(self)
self.button = QtGui.QPushButton('clickme', self)
self.layout().addWidget(self.lineEdit)
self.layout().addWidget(self.button)
self.button.clicked.connect(self.testSleep)
def testSleep(self):
self.lineEdit.setText('Start')
QtCore.QTimer.singleShot(2000, lambda: self.lineEdit.setText('End'))
def mainLoop(self, app ):
sys.exit( app.exec_())
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Ventana()
window.show()
sys.exit(app.exec_())
Also, take a look at the QThread sleep() function, it puts the current thread to sleep and allows other threads to run. https://doc.qt.io/qt-5/qthread.html#sleep
You can't use time.sleep here because that freezes the GUI thread, so the GUI will be completely frozen during this time.You can use QtTest module rather than time.sleep().
from PyQt4 import QtTest
QtTest.QTest.qWait(msecs)
So your code should look like:
from PyQt4 import QtGui,QtTest
from gui import *
class Ventana(QtGui.QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
QtGui.QWidget.__init__(self, parent)
self.setupUi(self)
self.button.clicked.connect(self.testSleep)
def testSleep(self):
import time
self.lineEdit.setText('Start')
QtTest.QTest.qWait(2000)
self.lineEdit.setText('Stop')
def mainLoop(self, app ):
sys.exit( app.exec_())
if __name__ == '__main__':
import sys
app = QtGui.QApplication(sys.argv)
window = Ventana()
window.show()
sys.exit(app.exec_())
This is PyQT code that I have to be executed in Spyder. The first time, I executed it, it works well. On the second time, it says:
QWidget: Must construct a QApplication before a QPaintDevice "
I searched for solution but nothing worked for me.
from PyQt4 import QtGui, QtCore
import sys
class Window(QtGui.QWidget):
def __init__(self):
QtGui.QWidget.__init__(self)
self.button = QtGui.QPushButton('Test', self)
self.button.clicked.connect(self.handleButton)
layout = QtGui.QVBoxLayout(self)
layout.addWidget(self.button)
def handleButton(self):
print ('Hello World')
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
window = Window()
window.show()
app.exec_()
#sys.exit(app.exec_())
I even commented sys.exit() which some people proposed. Could someone help me to get rid of this error as I am restarting the kernel every other time to execute.
First, your example is not really minimal. You'll observe, that
from PyQt4 import QtGui
if __name__ == '__main__':
app = QtGui.QApplication([])
w = QtGui.QWidget()
w.show()
app.exec_()
already does the trick.
My guess is that the console in which you let this script run twice is not deleting the QApplication (type app in the console you see the variable is still there).
In the second run, the newly created QApplication interferes with the still existing from the old run. They all run within the same console and it depends a bit on what spyder does when running a file.
To circumvent this delete the app before another run:
del app
I realize this is a bit of a vague question, but I'm not sure how to make it more specific.
The skeleton for my code is below:
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *
class FormWidget(QWidget):
def __init__(self, parent):
super(FormWidget, self).__init__(parent)
class MainWindow(QMainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
form = FormWidget(self)
self.setCentralWidget(form)
[do a bunch of stuff with form]
if __name__ == '__main__':
app = QApplication(sys.argv)
mainWindow = MainWindow()
mainWindow.show()
sys.exit(app.exec_())
Within the FormWidget class, there is a keyPressEvent() method that traps keyboard input, and on a specific key ('q'), calls this:
mainWindow.close()
Most of the time, that causes the app to exit, as desired. But occasionally (with no predictable pattern that I can discern), it causes a crash (dialog comes up that says 'python.exe has stopped working', with a 'Close program' button).
First question, I guess, is: Is this not the proper way to terminate a PyQt GUI app?
If it is, then second question is: Presumably, my code is misbehaving somewhere. But I'm not sure what sort of misbehavior to be looking for. What sort of mistake could I be making that would cause this?
Any thoughts appreciated.
/John
I managed to create and thread a PyQt application to do some screenshots of a list of urls. It's working really good, but it's always crashing on some websites (or at least on for sure).
Softpedia.com is one of them. It's just crashing Python with a segmentation fault just before the loadFinished event. Even if I don't use my threaded application but "raw" PyQt.
I tested with basic PyQt based browser I found on the web and I got the same issue.
Does anybody have an idea? I'm starting to think that this may be a dead end, which is not really a good news.
Thank you all!
There's probably some kind of issue with the the code you are using, this code shouldn't raise errors:
#!/usr/bin/env python
#-*- coding:utf-8 -*-
from PyQt4 import QtCore, QtGui, QtWebKit
class MyWindow(QtGui.QMainWindow):
def __init__(self, parent=None):
super(MyWindow, self).__init__(parent)
self.barProgress = QtGui.QProgressBar(self)
self.barProgress.setFixedSize(80, 15)
self.barProgress.setVisible(False)
self.barStatus = QtGui.QStatusBar(self)
self.barStatus.addPermanentWidget(self.barProgress)
self.webView = QtWebKit.QWebView(self)
settingsWeb = [
QtWebKit.QWebSettings.PluginsEnabled
]
for setting in settingsWeb:
self.webView.settings().setAttribute(setting, True)
self.setStatusBar(self.barStatus)
self.setCentralWidget(self.webView)
self.webView.loadFinished.connect(self.on_webView_loadFinished)
self.webView.loadFinished.connect(self.barProgress.hide)
self.webView.loadStarted.connect(self.barProgress.show)
self.webView.loadProgress.connect(self.barProgress.setValue)
#QtCore.pyqtSlot()
def on_webView_loadFinished(self):
QtGui.QMessageBox.information(None, "Info", "Load finished!")
def loadUrl(self, url):
self.webView.load(QtCore.QUrl(url))
if __name__ == "__main__":
import sys
app = QtGui.QApplication(sys.argv)
app.setApplicationName('MyWindow')
main = MyWindow()
main.show()
main.loadUrl("http://www.example.com/")
sys.exit(app.exec_())
There is an endless block when xml.etree.ElementTree.fromstring() function is called in the QThread. Also lots of other calls makes the QThread blocked like multiprocessing.Process().
Important to say that it is a pure block, no exception or break.
Here is the code (a little edited but same principle as the source):
from PyQt4.QtGui import *
from Ui_mainwindow import Ui_MainWindow
import sys
import xml.etree
class Bruton(QThread):
def __init__(self, mw):
super(Bruton, self).__init__(mw)
self.mw = mw
def run(self):
print("This message I see.")
tree = xml.etree.ElementTree.fromstring("<element>text</element>")
print("But this one never.")
class MainWindow(QMainWindow):
def __init__(self):
QMainWindow.__init__(self)
self.ui = Ui_MainWindow()
self.ui.setupUi(self)
self.init_bruton()
# When the form is shown...
def showEvent(self, arg1):
self.bruton.start()
def init_bruton(self):
self.bruton = Bruton(self)
app = QApplication(sys.argv)
mw = MainWindow()
mw.show()
sys.exit(app.exec_())
The code as posted doesn't actually run, but with a couple minor changes it runs and works fine. Here is the code with modifications:
from PyQt4.QtGui import *
from PyQt4.QtCore import *
import sys
import xml.etree.ElementTree
class Bruton(QThread):
def __init__(self, mw):
super(Bruton, self).__init__(mw)
self.mw = mw
def run(self):
print("This message I see.")
tree = xml.etree.ElementTree.fromstring("<element>text</element>")
print("But this one never.")
class MainWindow(QMainWindow):
def __init__(self):
QMainWindow.__init__(self)
self.init_bruton()
# When the form is shown...
def showEvent(self, arg1):
self.bruton.start()
def init_bruton(self):
self.bruton = Bruton(self)
app = QApplication(sys.argv)
mw = MainWindow()
mw.show()
sys.exit(app.exec_())
And here is the output:
$ python test.py
This message I see.
But this one never.
This is with Python 2.6.6, PyQt4 4.8.3, on Debian Unstable.
Can you try it in your environment and see if my modified example works for you? If so, you are on the road to a solution for your real code. =)
The code I've shown here is shortened (the source is divided to two files and __ini__.py). I noticed that the main module must be the module that starts the QApplication. So I added app.exec_() to the __init__.py which is the main module of my program.