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 user name and password in the pop-up dialog box, press the button on the login, if the username and password are correct then enter the main window, if there is wrong, the pop-up warn