在弹出对话框中填写用户名和密码，按下登录按钮，如果用户名和密码均正确则进入主窗口，如果有错则弹出警告对话框(Fill in the username and password in the pop-up dialog, press the login button and enter the main window if the username and password are correct, and if there is a mistake, the warning dialog box