PyQt4问题和使用Python登录到主窗口的窗口

Question

I'm new to PyQt and Python as a whole (more familiar with Java) and I'm trying to make an application where data is inserted and retrieved into the database. For the connection to the database, I'm using mysql connector. I'm able to insert and retrieve data just fine but I'm not sure how to implement the GUI portion of my application. What I want to do is have a login window that connected to the database for the main window to then insert data read from the file into the database and retrieve data based on what was selected by the user. Clicking "Sign in" should close the Login Window and open the Main Windows which shows a progress bar while inserting and should display results which users can sort by ( have not implemented it yet.

What are ways I could improve my program? My program sometimes hangs.

How could I go about my approach?

Is there an equivalent to Java's JFrame.dispose() in Python which closes then Window and clicking on a button?

The Login Window:

import sys
from PyQt4 import QtGui, QtCore
from PyQt4.Qt import QPushButton, QLabel
from PyQt4.QtGui import QPlainTextEdit
from PyQt4.QtGui import QLineEdit
from MainGUI import MainGUI
import time

class LoginGUI(QtGui.QMainWindow):

    def __init__(self):
        super(LoginGUI, self).__init__()
        self.setGeometry(730, 350, 500, 300)
        self.setWindowTitle("Login")
        self.initGUI()

    def initGUI(self):

        titleLabel = QLabel("Login", self)
        titleLabel.move(200, 20)
        titleLabel.setFont(QtGui.QFont("", 20))

        loginLabel = QLabel("Username: ", self)
        loginLabel.move(135, 120)

        passwordLabel = QLabel("Password: ", self)
        passwordLabel.move(135, 150)

        loginText = QPlainTextEdit("root", self)
        loginText.move(195, 120)

        passwordText = QLineEdit("",self)
        passwordText.move(195, 150)
        passwordText.setEchoMode(QtGui.QLineEdit.Password)

        loginBtn = QtGui.QPushButton("Sign in", self)
        loginBtn.clicked.connect(lambda: 
              self.connectToDB(loginText.toPlainText(), passwordText.text()))
        loginBtn.resize(loginBtn.sizeHint())
        loginBtn.move(170, 250)

        quitBtn = QtGui.QPushButton("Quit", self)
        quitBtn.clicked.connect(QtCore.QCoreApplication.instance().quit)
        quitBtn.resize(quitBtn.sizeHint())
        quitBtn.move(245,250)

        self.show()

    def connectToDB(self,username,password):
        pmg = MainGUI()
        pmg.prep("D:\\folder\\data.csv", username, password)
        pmg.run()
        #logonGUI.close()
        #mainApp = QtGui.QApplication(sys.argv)
        #mainGUI = MainGUI()
        #sys.exit(app.exec_())
        #return pmg      

if __name__ == '__main__':
    app = QtGui.QApplication(sys.argv)
    logonGUI = LoginGUI()
    sys.exit(app.exec_())  

The Main Window:

other imports
import sys
from PyQt4 import QtGui, QtCore
from PyQt4.Qt import QPushButton, QLabel
from PyQt4.QtGui import QPlainTextEdit
from PyQt4.QtCore import QEventLoop
from viewer.DataSource import DataSource

class MainGUI(QtGui.QMainWindow):

    theFile = None

    username = None

    password = None

    source = None

    con = None

    rowsInserted = 0

    progressBar = None

    completed = 0

    def __init__(self):

        #app = QtGui.QApplication(sys.argv)
        #mainGUI = MainGUI()
        #sys.exit(app.exec_()).

        super(MainGUI, self).__init__()
        self.setGeometry(730, 350, 1000, 600)
        self.setWindowTitle("MainWindow")
        self.initGUI()
        #self.show()


    def prep(self, x, username, password):
        try:
            self.theFile = open(x, "r")

            self.username = username

            self.password = password

            #Connect to db and pass connection to each class.
            #Close connection at the end in a Finally statement.

            self.source = DataSource()

            self.con = self.source.getConnection(username, password)


        except FileNotFoundError:
            print("No file of {} found.".format(x))  

    def initGUI(self):
            titleLabel = QLabel("MainWindow", self)
            titleLabel.resize(200, 20)
            titleLabel.move(450, 30)
            titleLabel.setFont(QtGui.QFont("", 20))
            quitBtn = QtGui.QPushButton("Quit", self)
            quitBtn.clicked.connect(QtCore.QCoreApplication.instance().quit)
            quitBtn.resize(quitBtn.sizeHint())
            quitBtn.move(800,550)

            self.progressBar = QtGui.QProgressBar(self)
            self.progressBar.setGeometry(200, 80, 250, 20)

    def run(self):        

        with self.theFile as data:
            lines = data.readlines()[1:]
            for line in lines:
            QtCore.QCoreApplication.processEvents(flags=QEventLoop.AllEvents)
            #Line with QtCore supposed to be indented.
            cleanDataFromDB(self.con)
            insertData(self.con)

dao.retrieve(userInput)

            try:
                if self.con != None:
                    self.con.close()
            except:
                print("Error closing the database.")    

Answer 1

I have found my solution. I have made my instance of the MainGUI global so that it doesn't close.

def connectToDB(self,username,password):
    global pmg
    pmg = MainGUI()
    pmg.prep("D:\\folder\\data.csv", username, password)
    pmg.run()
    self.close()

I have made some changes to my MainGUI itself by adding some show() statements to the title and button for before in initGUI() and after the loop of run(), and having repaint() after the show() after the loop.

def initGUI(self):
        titleLabel = QLabel("MainWindow", self)
        titleLabel.resize(200, 20)
        titleLabel.move(450, 30)
        titleLabel.setFont(QtGui.QFont("", 20))
        titleLabel.hide()

        quitBtn = QtGui.QPushButton("Quit", self)
        quitBtn.clicked.connect(QtCore.QCoreApplication.instance().quit)
        quitBtn.resize(quitBtn.sizeHint())
        quitBtn.move(800,550)
        quitBtn.hide()

        self.progressBar = QtGui.QProgressBar(self)
        self.progressBar.setGeometry(200, 80, 250, 20)
        self.progressBar.show()


def run(self):        

    with self.theFile as data:
        lines = data.readlines()[1:]
        for line in lines:
           QtCore.QCoreApplication.processEvents()
           cleanDataFromDB(self.con)
           insertData(self.con)
        progressBar.hide()
        titleLabel.show()
        quitBtn.show()
        self.repaint()

Thanks for taking your time to help me. :D