Apktool is a utility available on android for compile/decompile android applications.

It can extract dex (dalvik executable codes into) codes into smali (human readable form of dex code)

For viewing dex/smali codes. You need to open those files with 920 text editor. It’s my personal editor and I love it.

Download 920 text editor here

https://play.google.com/store/apps/details?id=com.jecelyin.editor.v2&hl=en

 Anyway, I’m thanking the developer of this app. You can meet him on xda.

For setting apktool,there is a prerequisite.
 You can only configure this app only by allowing Root access. And this is one of the main benefits of having root previlage :-)
If you already have it,just skip this words.

So lets start by downloading Apktool. You can download it from here.

https://code.google.com/archive/p/apktool/downloads?_e_pi_=7%2CPAGE_ID10%2C4820948118

This is a zip file,so extract  it in your root directory of your default  storage.

For eg:

In your android,goto storage option and check which is the ‘default writing disk’. Normally it is phone storage /mnt/phonestorage /apktool would be the folder location if your writing disk is phone.

And /mnt/sdcard/apktool would be the storage folder location if the storage is sdcard.

So extract it in root of the storage,not in any sub folders as I already mentioned.

Now Inside the folder,there is an application called ‘Apktool.apk '

Install it!

Then open the app and allow root permission.

This time,goto any filemanger which can navigate through system files. I personally recommend ‘ES File Explorer ‘.

NOTE:You should enable root explorer on the filemanger by going through the settings.

Now goto /system/framework/framework.Apk

Now,just copy framework.apk  and paste it on your Apktool folder that you had created.

After pasting it,open Apktool and just tap on framework.apk.  Then you will see an option  ‘import as framework’.

Select that option.

You are almost done now.

The last step is about to paste an apk to your working . Done! Now you can just tap on the app and select the option ‘decompile all’.

Now,a folder will be newly created. Basically, it is the folder associated with the decompiled apk.

Now you can just browse on to the folder and make changes.

After making proper changes,tap on the decompiled folder and select ‘Recompile All’.

Before, installing our modified application, we need to sign the apk.

For this,just tap on the recompiled apk and press ‘sign apk’.

After signing it,you could see a new apk named as ’example.apk_src_sign apk’.
Install  this file. That’s it.  You have now your app work station in your android.

Doubts ? Comment below!