(1. remote login (if the user name and password exceed 3 digits, it will succeed. You can set the code on the server by yourself) // 2. including the loading effect (multi-threaded processing, current events return data) // 3. unsuccessful login can prompt the error reason // 4. save the logged in information (such as user name and password, which can be set by yourself) // 5. super complete and detailed notes (novice can understand) // You can set it as your own UI Library)