登录界面,输入用户名，如过用户名不正确则重新输入用户名，正确后进入密码输入；如果密码不正确则重新显示输入密码，正确后显示welcome！-Login screen, enter a user name, such as the username is incorrect, re-enter your user name, enter the correct password input if the password is incorrect, re-enter the password co