Open the RE manager and copy the framework-res.apk from the system\framework folder to the SD card and directory.
Connect the computer, use winrar to directly open the framework-res.apk (do not extract it), and enter the res\drawable-mdpi folder (different mobile phone directories may be different, but they are all under the drawable prefix).
Find the picture that needs to be modified (all the icon materials called by the mobile phone are here), a picture with the same size as the screen of the mobile phone.
Make a good picture (modify the picture). The modified name is exactly the same as the name of the picture to be changed-including the extension.
Replace screen_background_dark_bak.jpg in the drawable-mdpi folder (directly pull the picture to be replaced into winrar to overwrite it).
5. Close winrar without signing.
6. Turn off USB mode, turn on re Manager, and right-click to copy the framework-res.apk
7. Press Enter to the system\framework directory, modify permissions (read and write), back up the framework-res.apk, and paste it into this directory.
8. You can see the effect after restarting.