1. Decompress the APK file with decompression software to get a folder named "META-INF" and a file named "classes.dex".
2. Modify the contents that need to be changed, and change pictures, codes, etc.
3. The code has been modified. You need to recompile the code with a compiler to generate a new "classes.dex" file.
4. Use zip compression software to repackage the changed contents into APK files, and delete the original "classes.dex" file and "META-INF" folder.
5. Sign the new APK file with the signature tool of V 1+V2 to generate a new signature APK.