Show a Loading Home Dialog before starting MainWindow

[hachbani]

Hi,

I have an app that parses a file and show data in QtableView. Before, I had a button in the mainwindow to load the source file. What I'm trying to implement now is a Dialog Window with only one button, the only purpose of this dialog window is to give a minimalistic and simple view to the user, where he can first select the file to be parsed and have a Loading progress bar (or something else) while the LoadData() function is runned. The Home Dialog should only be hidden/closed when the parsing is done.

What I'm achieving now:

• The Home dialog starts
• the user selects the file
• the Home dialog disappears
• LoadData is running
• when LoadData is finished, the MainWindow shows with the data being parsed and tables filled.

Which is very close to what I want, except the part when the Home Dialog disappears before LoadData gets executed.

Here's my code if anyone can help.

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        """
        ..
        __init__ code lines
        """
        self.hide()
        d = HomeDialog()
        if d.exec_():
            self.LoadData(d.path)

    def LoadData(self, file_path):
        """
        Parsing lines of code
        """

        #Parsing finished -> show the mainWindow
        self.show()

class HomeDialog(QtWidgets.QDialog, home_dialog.Ui_Dialog):
    def __init__(self, parent=None):
        super(HomeDialog, self).__init__(parent)
        self.setupUi(self)
        self.openB6.clicked.connect(self.get_file_name)

    def get_file_name(self):
        file_name = QtWidgets.QFileDialog.getOpenFileName(self, 'Open config file',
                                                            dir=path.join("/"),
                                                            filter="B6 (*.b6)")
        if not file_name[0]:
            return None
        else:
            self.path = file_name
            self.accept()

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle(ProxyStyle())
    mainWin = MainWindow()
    mainWin.show()
    sys.exit(app.exec_())

[SGaist]

Hi,

It looks a bit like a "mini-wizard" so you could use a QWizard for that.

Not that if you have a long running operation, you might want to use QtConcurrent::run to execute it and let the GUI show a QProgressBar or a QProgressDialog depending on the road you take.

[hachbani]

Hi @SGaist ,

I've been looking at QWizard, not sure if this is what i'm looking for, in addition to that, I gave it a try but struggling hard to implement it. Is there now other classes I can use ?

[JonB]

@hachbani
Look at the QProgressBar/QProgressDialog alternative approach @SGaist suggested. That is the usual way to show the user when a background operation is running.

[hachbani]

@JonB

i've looking into QProgressDialog, the progressDialog is shown but not updated. From what I saw on several forums posts: do I have to use a QThread as well ?

Here's my code:

class progressBar(QtWidgets.QProgressDialog):
    def __init__(self, parent= None):
        super(progressBar, self).__init__(parent)
        pd = QtWidgets.QProgressDialog('loading...', 'cancel', 0, 100, self)

class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
    def __init__(self, parent=None):
        """
        ..
        __init__ code lines
        """
        self.hide()
        d = HomeDialog()
        if d.exec_():
            self.LoadData(d.path)

    def LoadData(self, file_path):
        progress = progressBar()
        progress.show()
        progress.setValue(1)
        """
        Parsing lines of code
        progress.setValue(30)
        ..
        ..
        progress.setValue(70)
        ..
        ..
        """
        progress.hide()
        #Parsing finished -> show the mainWindow
        self.show()

class HomeDialog(QtWidgets.QDialog, home_dialog.Ui_Dialog):
    def __init__(self, parent=None):
        super(HomeDialog, self).__init__(parent)
        self.setupUi(self)
        self.openB6.clicked.connect(self.get_file_name)

    def get_file_name(self):
        file_name = QtWidgets.QFileDialog.getOpenFileName(self, 'Open config file',
                                                            dir=path.join("/"),
                                                            filter="B6 (*.b6)")
        if not file_name[0]:
            return None
        else:
            self.path = file_name
            self.accept()

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle(ProxyStyle())
    mainWin = MainWindow()
    mainWin.show()
    sys.exit(app.exec_())

[jsulm]

@hachbani said in Show a Loading Home Dialog before starting MainWindow:

class progressBar(QtWidgets.QProgressDialog):
def init(self, parent= None):
super(progressBar, self).init(parent)
pd = QtWidgets.QProgressDialog('loading...', 'cancel', 0, 100, self)

Why do you create an instance of QtWidgets.QProgressDialog in progressBar which is already itself a QtWidgets.QProgressDialog?!

"do I have to use a QThread as well ?" - depends on how you process.

[hachbani]

To be honest I don't really know, for aesthetic reasons I guess, I've tried without creating the class (pd=QtWidgets.QProgressDialog('loading...', 'cancel', 0, 100, self) ) in the LoadData function. I get the same result

[jsulm]

@hachbani said in Show a Loading Home Dialog before starting MainWindow:

for aesthetic reasons I guess

Aesthetic reasons? There is absolutely no need for this pd - you are basically creating TWO progress dialogs (but only show one).
Why it does not work: well, you do not show how you process the data after showing progress dialog...

[jsulm]

@hachbani Basic approach is: show progress dialog, start your long lasting operation, on each iteration emit a signal which is connected to https://doc.qt.io/qt-5/qprogressdialog.html#value-prop slot.

[hachbani]

I updated the code a follow:

created a signal: self.change_val = QtCore.Signal(int) and connected it to a slot set_progress_val

in the LoadData, I emit change_val signal at different places.

Also did some changes in the if name == 'main'

class MainWindow(QtWidgets.QMainWindow,  Ui_MainWindow):

    change_val = QtCore.Signal(int)
    def __init__(self, file_name,parent=None):
        """
        super(MainWindow, self).__init__(parent)
        ..
        __init__ code lines
        """

        change_val.connect(self.set_progress_val)
        self.progress = QtWidgets.QProgressDialog('loading...', 'cancel', 0, 100, self)
        self.progress.show()
        self.LoadData(d.path)
    
    @QtCore.Slot(int)
    def set_progress_val(self, val):
        self.progress.setValue(val)

    def LoadData(self, file_path):
        
        """
        Parsing lines of code
        ..
        change_val.emit(30)
        ..
        ..
        change_val.emit(60)
        ..
        ..
        """
        self.progress.hide()
        #Parsing finished -> show the mainWindow
        self.show()

class HomeDialog(QtWidgets.QDialog, home_dialog.Ui_Dialog):
    def __init__(self, parent=None):
        super(HomeDialog, self).__init__(parent)
        self.setupUi(self)
        self.openB6.clicked.connect(self.get_file_name)

    def get_file_name(self):
        file_name = QtWidgets.QFileDialog.getOpenFileName(self, 'Open config file',
                                                            dir=path.join("/"),
                                                            filter="B6 (*.b6)")
        if not file_name[0]:
            return None
        else:
            self.path = file_name
            self.accept()

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle(ProxyStyle())
    d = HomeDialog()
    if d.exec_():
        mainWin = MainWindow(file_name=d.path)
        mainWin.show()
        sys.exit(app.exec_())

I get the following error: 'str' object has no attribute 'connect'

[JonB]

@hachbani
On which line? self.change_val[int].connect(self.set_progress_val)? Are you using PyQt5, PySide2, or what?

[hachbani]

I'm using Pyside2, pyothn 3.8

I get the error on the follwoing line mainWin = MainWindow(file_name=d.path)

[hachbani]

The idea of self.change_val[int].connect(self.set_progress_val) is that when i'm going to call self.change_val.emit(20), the set_progress_val is called with 20 as argument, maybe I'm implementing this wrong

[JonB]

@hachbani
I'll look into the possible connect() issue in a moment. But

I get the error on the follwoing line mainWin = MainWindow(file_name=d.path)

mainWin = MainWindow(file_name=d.path)

I don't see your MainWindow.init() has a file_name argument?

Actually, before I look, could we establish where exactly this error is really coming from? With print() statements/debugger, do you actually get to the self.change_val[int].connect(self.set_progress_val) line at all? Or is the error really that constructor line??

[hachbani]

Just a pasting mistake, I updated the code in my last comment.

if I remove all the progressBar code parts, the program will run successfully, but with nothing being shown while the LoadData function is runnung

[JonB]

@hachbani

class MainWindow(QtWidgets.QMainWindow, file_name, Ui_MainWindow):
    def __init__(self, parent=None):

How do you manage file_name in the class declaration? How do you not have it in the __init__()? I'm not going to guess if this is in fact not the code you have, that's what pasting is for....

[hachbani]

@JonB said in Show a Loading Home Dialog before starting MainWindow:

Actually, before I look, could we establish where exactly this error is really coming from? With print() statements/debugger, do you actually get to the self.change_val[int].connect(self.set_progress_val) line at all? Or is the error really that constructor line??

I added a print before and after the connect line, I get the first print and then the 'str' object has no attribute 'connect'

the file_name argument gets passed to LoadData at the end of MainWindow __init__()

[JonB]

@hachbani said in Show a Loading Home Dialog before starting MainWindow:

the file_name argument gets passed to LoadData at the end of MainWindow init()

class MainWindow(QtWidgets.QMainWindow, file_name, Ui_MainWindow):

I don't understand. It's not an "argument", is it? You have it in the list of classes from which MainWindow derives?? Unless your knowledge of Python is better than mine.

[hachbani]

Sorry sorry, feel ridiculous, it was a mistake, the file_name is indeed an argument to MainWindow init(). I corrected the code in the comment. It was in init in my code, just a rookie mistake while making the minimalistic code

[JonB]

@hachbani
Please understand, we have to get pasting/correct code right! When you've tried to help in this forum for as much as I have you never know what posters have actually got if it's not accurate, and I have wasted too much time over the years answering questions about user code which is not actually the code! :)

I'll think about your connect() now....