No files visible in the QFileDialog window

Question

I am writing a simple code using pyqt

In the code, I invoke a QFileDialog, however when I invoke it using the static functions all works fine, but with the normal method i.e. using dialog.exec_(), I do not see any files in the file dialog window.

Only after typing the complete path of the file can I see the file in the file dialog window. Note that this issue is only when I invoke the FileDialoghandler function, If I don't do that, no matter how I invoke the QFileDialog, everything works fine. And also this issue is only on Linux, on Windows7 everything works ok. I am wondering whether this is a PyQt bug or am I missing something here?

Code is as follows:

import sys
from PyQt4.QtCore import Qt
from PyQt4.QtGui import *
from PyQt4.QtCore import QAbstractFileEngine
from PyQt4.QtCore import QAbstractFileEngineHandler
from PyQt4.QtCore import QFSFileEngine

class FileDialogHandler(QAbstractFileEngineHandler):
    def create(self,filename):
        if str(filename).startswith(':'):
            return None # Will be handled by Qt as a resource file
        print("Create QFSFileEngine for {0}".format(filename))  
        return QFSFileEngine(filename)

class Example(QMainWindow):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):      

        self.textEdit = QTextEdit()
        self.setCentralWidget(self.textEdit)
        self.statusBar()

        openFile = QAction(QIcon('open.png'), 'Open', self)
        openFile.setShortcut('Ctrl+O')
        openFile.setStatusTip('Open new File')
        openFile.triggered.connect(self.showDialog)

        menubar = self.menuBar()
        fileMenu = menubar.addMenu('&File')
        fileMenu.addAction(openFile)       

        self.setGeometry(300, 300, 350, 300)
        self.setWindowTitle('File dialog')
        self.show()

    def showDialog(self):
        handler = FileDialogHandler()
        #using QFileDialog.getOpenFileName works fine
        fname = QFileDialog.getOpenFileName(None, 'Open file', '/home','All files (*.*)')
        #dialog = QFileDialog()
        #dialog.setOption(QFileDialog.DontUseNativeDialog,False)
        #if dialog.exec_():
            #fname = dialog.selectedFiles()
        #else:
            #fname = None
        f = open(fname, 'r')        
        with f:        
            data = f.read()
            self.textEdit.setText(data) 

def main():
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()

Answer 1

I encountered a similar problem not long ago with the getOpenFilename. For me the solution was to change the backend from native to Qt's own implementation of the dialog. This can be achieved withan extended calling syntax which looks like:

filename = QtGui.QFileDialog.getOpenFileName(self,
                                             'Open file',
                                             '/home',
                                             'All files (*.*)',
                                             options=QtGui.QFileDialog.DontUseNativeDialog)

After I changed to this calling syntax I never had any problems again.