1.

Download apktool

And setting environment variables.

2.

The command line enters the apk directory and executes: apktool.

d

xx.apk

(If you encounter some errors, it means that apk has done anti-cracking processing. )

3.

After successful execution, xx folder will be generated. Enter the xx folder to modify the contents that need to be modified. If you need to modify the code, enter xx\smali\, and you need to know some smali syntax.

4.

After modification, return to the command line and execute: apktool.

b

xx

A dist folder will be generated under the xx folder, and the apk in it will be compiled back. This apk is unsigned.

5.

Download the online signature tool to sign the apk, and then you can install it (if you download the source code or sdk, you can also sign it with signapk).