PyQT LineEdit输入验证，阻止用户退格

Question

嗨，为了学习，我创建了这个基本程序来ping一个在Windows上运行的主机。

请批评并纠正。

我最关心的是disable_button函数。

我确保“line_edit_hostname”中的输入仅在用户输入的字符串中包含1个字符并且具有“。”时才有效。在文中。

我这样做的原因是因为当我输入一个没有'。'的字符串时ping崩溃了。

然而，有一种解决方法，一旦用户输入一个包含多个字符和'。'的字符串，他们就可以点击退格按钮然后继续该程序。

我打算在disable_button函数上放置一个while循环，因此它可以关注文本验证，但这似乎会使程序崩溃。

阅读之后，我认为它与在函数disable_button函数中没有使用的线程有关。我尝试了标准的线程模块并没有取得任何进展，因此我发现自己在这里寻求帮助：）

如果有人可以通过正确的线程纠正它，或者甚至可以重新编写一个更好的版本，我可以从中学到很棒。

感谢您的时间。

#!python3

import subprocess
import sys

from PyQt4 import QtGui
from PyQt4.QtCore import *
from PyQt4.QtGui import *

# import threading

""" An example of a GUI Program that can ping a host """


# Class for the Application
class NetworkCheck(QDialog):

    def __init__(self):
        QDialog.__init__(self)

        # make it a vertical box layout in the main form
        layout = QVBoxLayout()

        # Widgets
        # When we add self in front of a Variable they become instance wide
        self.label_hostname = QLabel("Please enter a Hostname")
        self.line_edit_hostname = QLineEdit()
        self.label_ip = QLabel("Host IP Address:")
        self.line_edit_ip_address = QLineEdit()
        self.btn_ok = QPushButton("Ok")
        self.btn_clear = QPushButton("Clear")
        self.btn_exit = QPushButton("Exit")

        # Always add PlaceHolder Text before adding
        # The Widget to the layout
        self.line_edit_hostname.setPlaceholderText("example.com")
        self.line_edit_hostname.setAlignment(Qt.AlignHCenter)
        # calls the text_input function we defined to control the input of text to
        # make sure it has a "." so the program doesn't crash...
        self.line_edit_hostname.setText("")

        # When results show in the IP Address and Set it as a Read Only Field..
        self.line_edit_ip_address.setAlignment(Qt.AlignHCenter)
        self.line_edit_ip_address.setReadOnly(True)

        # Align the Labels in the Center of the Window'
        self.label_hostname.setAlignment(Qt.AlignHCenter)
        self.label_ip.setAlignment(Qt.AlignHCenter)

        # Now we need to add the above Widgets to the Form
        layout.addWidget(self.label_hostname)
        layout.addWidget(self.line_edit_hostname)
        layout.addWidget(self.label_ip)
        layout.addWidget(self.line_edit_ip_address)
        layout.addWidget(self.btn_ok)
        layout.addWidget(self.btn_clear)
        layout.addWidget(self.btn_exit)

        # Now we need to Save the Layout
        self.setLayout(layout)

        # Change the Main Window Title Name
        self.setWindowTitle("Check Host")

        # Removes the Focus from QLineEdit()
        # This means that the text will always display
        # in the QLineEdit field
        self.setFocus()

        # Stop the Window from being Stretched
        # Sets the Width to 250 by 200 Height
        self.setFixedSize(250, 200)

        # Exit button to close the Main window
        self.btn_exit.clicked.connect(self.close)

        # Clear Button will clear the line edit fields and disable the Ok button
        self.btn_clear.clicked.connect(self.clear_fields)

        # Ok button to perform the function...
        # disables the button by default..
        self.btn_ok.setEnabled(False)
        # if Text is entered in the hostname field it calls the disable_button function
        # and a "." is also entered in the line_edit field..
        self.line_edit_hostname.textChanged.connect(self.disable_button)

    def clear_fields(self):
        """Clear the Line Edit Boxes.. and Disables the Ok push button"""
        self.line_edit_hostname.setText("")
        self.line_edit_ip_address.setText("")
        self.btn_ok.setEnabled(False)

    def get_ip(self):
        try:

            # defines the hostname variable to use in the command
            hostName = self.line_edit_hostname.displayText()

            ping = subprocess.Popen(
                ["ping", "-n", "1", hostName],
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE
            )

            # output of the above command
            ping_output, error = ping.communicate()

            # get rid of the bytes output...
            ping_output = ping_output.decode("utf-8")

            # Clean the output to get the IP only...
            ip_start = ping_output.index("[") + 1
            ip_end = ping_output.index("]")

            # get only the ip address..
            # global ip_output
            ip_output = ping_output[ip_start:ip_end]

            # displays the ip address in the line_editip_address field.
            self.line_edit_ip_address.setText(ip_output)

        except Exception:
            # Dialog Box: adds the Title and the Massage...
            QMessageBox.warning(self, "Warning", "The Ping Lookup Failed...")
            # Terminates the Application...
            sys.exit()
            # return

    # enables the button get results once text has been entered in the line edit field hostname
    # and a "." is also entered in the line_edit field..
    def disable_button(self):
        # while True:
        if len(self.line_edit_hostname.text()) > 0 and "." in str(self.line_edit_hostname.text()):
            # if the text is greater then 1 char it enables the button
            self.btn_ok.setDisabled(False)
            # connect to the "OK" button we crated the in the UI and calls the get_ip function
            self.btn_ok.clicked.connect(self.get_ip)
            # break


# Calling the Application Class
if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = NetworkCheck()
    # enable threading on the get_ip function from the Window class that holds the application.
    # t1 = threading.Thread(target=window.get_ip)
    # t1.start()
    # t1.join()
    window.show()
    app.exec_()