How to change Apple's mobile phone to a new one?

As long as the old and new mobile phone systems are above iOS 12, turn on the Bluetooth function of the two mobile phones and put them together. After the new phone is turned on, set the Apple ID and password of the new phone to be the same as the old phone, and then the system will ask you if you want to transfer the data. After you confirm, all kinds of data of the old mobile phone will be automatically transferred to the new mobile phone, and photos, address books and even downloaded apps will be copied to the new mobile phone. The only difference in the whole interface is that all apps need to log in again, and the chat records of various instant messaging software are gone. There are no recent calls in the address book, and the SMS database is empty. Unless you upload these to iCloud before, they won't be randomly transferred.