Python - 按钮内部的IF函数

Question

我有一个下面的代码有问题。默认情况下，它是一个简单的代码，用于切换帧。我试图做的是修改LoginPage类来完成它所说的 - login;），正如你所看到的，我有一个test.db SQL数据库。它包含具有列的表用户：（Id INT，Name TEXT，Password TEXT） 我需要做的是输入登录名和密码，并将其与数据库中的用户进行比较。之后将它们指向LoginSuccessful或LoginFailed框架。问题在于，每当我接近这门课时，我都会制动代码。

我完全不知道如何在按钮内插入IF语句。

只是为了澄清：它还没有加密（这只是一个学校项目），所以你不必提及它是不安全的，因为我很清楚这一点:) 任何人有任何想法？

import tkinter as tk 
import sqlite3 as lite 
import sys 
from Crypto.Cipher import AES 

con = None 
con = lite.connect('test.db') 
cur = con.cursor() 


TITLE_FONT = ("Helvetica", 18, "bold") 

class SampleApp(tk.Tk): 

    def __init__(self, *args, **kwargs): 
     tk.Tk.__init__(self, *args, **kwargs) 

     # the container is where we'll stack a bunch of frames 
     # on top of each other, then the one we want visible 
     # will be raised above the others 
     container = tk.Frame(self) 
     container.pack(side="top", fill="both", expand=True) 
     container.grid_rowconfigure(0, weight=1) 
     container.grid_columnconfigure(0, weight=1) 

     self.frames = {} 
     for F in (LoginPage, LoginSuccessful, LoginFailed): 
      page_name = F.__name__ 
      frame = F(parent=container, controller=self) 
      self.frames[page_name] = frame 

      # put all of the pages in the same location; 
      # the one on the top of the stacking order 
      # will be the one that is visible. 
      frame.grid(row=0, column=0, sticky="nsew") 

     self.show_frame("LoginPage") 

    def show_frame(self, page_name): 
     '''Show a frame for the given page name''' 
     frame = self.frames[page_name] 
     frame.tkraise() 


class LoginPage(tk.Frame): 

    def __init__(self, parent, controller): 
     tk.Frame.__init__(self, parent) 
     self.controller = controller 
     label = tk.Label(self, text="This is the login page", font=TITLE_FONT) 
     label.pack(side="top", fill="x", pady=10) 
     inst_lbl = tk.Label(self, text = "Please enter your login credentials") 
     inst_lbl.pack() 
     pwa = tk.Label(self, text = "Login") 
     pwa.pack() 
     login = tk.Entry(self) 
     login.pack() 
     pwb = tk.Label(self, text = "pPassword") 
     pwb.pack() 
     password = tk.Entry(self) 
     password.pack() 
     button1 = tk.Button(self, text="Log in", 
          command=lambda: controller.show_frame("LoginSuccessful")) 
     button1.pack() 



class LoginSuccessful(tk.Frame): 

    def __init__(self, parent, controller): 
     tk.Frame.__init__(self, parent) 
     self.controller = controller 
     label = tk.Label(self, text="Login was successful!", font=TITLE_FONT) 
     label.pack(side="top", fill="x", pady=10) 
     button = tk.Button(self, text="Go to the Login page", 
          command=lambda: controller.show_frame("LoginPage")) 
     button.pack() 


class LoginFailed(tk.Frame): 

    def __init__(self, parent, controller): 
     tk.Frame.__init__(self, parent) 
     self.controller = controller 
     label = tk.Label(self, text="Login failed!", font=TITLE_FONT) 
     label.pack(side="top", fill="x", pady=10) 
     button = tk.Button(self, text="Go to the Login page", 
          command=lambda: controller.show_frame("LoginPage")) 
     button.pack() 



if __name__ == "__main__": 
    app = SampleApp() 
    app.mainloop() 

Answer 1

考虑添加方法checkLogin，而不是一个匿名lambda功能目前始终打开成功屏。这种方法将运行参数化的SQL查询来检查凭证，并根据结果调用登录成功或失败的框架：

SELECT 1 FROM users WHERE [Name] = ? AND [Password] = ? 

然后，让登录按钮调用此方法。一个重要的项目是用self.来限定所有类变量，因此checkLogin可以使用返回的框架用户输入值返回LoginPage。下面是LoginPage类的调整，唯一需要改变的：

class LoginPage(tk.Frame): 

    def __init__(self, parent, controller): 
     tk.Frame.__init__(self, parent) 
     self.controller = controller 
     self.label = tk.Label(self, text="This is the login page", font=TITLE_FONT) 
     self.label.pack(side="top", fill="x", pady=10) 
     self.inst_lbl = tk.Label(self, text = "Please enter your login credentials") 
     self.inst_lbl.pack() 
     self.pwa = tk.Label(self, text = "Login") 
     self.pwa.pack() 
     self.login = tk.Entry(self) 
     self.login.pack() 
     self.pwb = tk.Label(self, text = "pPassword") 
     self.pwb.pack() 
     self.password = tk.Entry(self) 
     self.password.pack() 

     button1 = tk.Button(self, text="Log in", command=self.checkLogin) 
     button1.pack() 

    def checkLogin(self): 
     cur.execute("SELECT 1 FROM users WHERE [Name] = ? AND [Password] = ?", 
        [self.login.get(), self.password.get()]) 
     result = cur.fetchone() 

     if result is None: 
      self.controller.show_frame("LoginFailed") 
     else: 
      self.controller.show_frame("LoginSuccessful")