I highly recommend using APK Tool M to decompile the growtopia apk. Or you can get growtopia with edited: Growtopia Folder, so you don't need to do the tutorial below.

1. Antisplit the apk

If you see a split sign like the picture below then follow these steps:

Click the growtopia apk and press antisplit as shown below:

Select the apk signature as shown below:

And install the growtopia apk.

2. Decompile growtopia apk

Click the growtopia apk and press decompile as shown below:

Do what the image below does:

And press go to:

3. Add your library to apk

Copy the library file (.so) from libs to the target game. Watch out the folder names, we don't want to mix them up, so make sure to copy our lib file to the correct architecture. Like our armeabi-v7a lib goes to the target games armeabi-v7a folder, arm64-v8a lib goes to the arm64-v8a folder...

PUTTING THE LIB FILE ON A WRONG ARCHITECTURE LIKE PUTTING ARM64 LIB TO ARMV7 WILL RESULT A CRASH!

Now go to lib/{arch}:

You can use second tab to copy library file to target game lib:

And paste library file to target game lib:

4. Load your library

Now go to smali/com/rtsoft/growtopia:

and open the Main.smali file, Add this code before const-string v0, "growtopia".

const-string v0, "ModMenu"

invoke-static {v0}, Ljava/lang/System;->loadLibrary(Ljava/lang/String;)V

Like the picture below:

5. Compiling game apk

Now compile and sign the apk, and install it on your device. Congrats. You have successfully implemented a mod menu.

Later ok?