[Galaxy S6 Themes and Apps] JusTeN_:
Hello :) well.. I am starting developing, so I took 2 apps that coming with MultiWindow feature, after looking about the things similar in the androidmanifest.xml I took 1 app that come without MultiWindow feature, added the similar things and recompiled, signed, installed and there it was.. MultiWindow feature :)

SO... Tools needed:

Apktool.bat

Apktool.jar

Signapk.zip
​

Step 1​

Create your apktool.bat file as I cannot upload it, bat files can be viruses so it is not allowed.

Create txt file, paste this code inside:

@echo off
if "%PATH_BASE%" == "" set PATH_BASE=%PATH%
set PATH=%CD%;%PATH_BASE%;
java -jar -Duser.language=en "%~dp0\apktool.jar" %1 %2 %3 %4 %5 %6 %7 %8 %9

Save, change the extension from txt to bat.

Step 2​

Download apk file, paste it in the same folder with apktool.bat and apktool.jar, call this folder Apktool :P

Press Shift + empty space inside the folder and then choose open cmd here / open cmd and navigate to this folder using the line "cd C:\Users\....."

in the cmd type "Apktool d yourappname.apk" this will decompile the app and create a new folder named "yourappname" inside it there will be androidmanifest.xml , edit it (recommending notepad++).

Step 3​

Modifying the androidmanifest file.

Scroll down as you can before the line closing application (looks like "</Application>")

add this lines:

<uses-library android:name="com.sec.android.app.multiwindow" android:required="false"/>
<meta-data android:name="com.sec.android.support.multiwindow" android:value="true"/>
<meta-data android:name="com.sec.android.multiwindow.DEFAULT_SIZE_W" android:resource="@dimen/app_defaultsize_w" />
<meta-data android:name="com.sec.android.multiwindow.DEFAULT_SIZE_H" android:resource="@dimen/app_defaultsize_h" />
<meta-data android:name="com.sec.android.multiwindow.MINIMUM_SIZE_W" android:resource="@dimen/app_minimumsize_w" />
<meta-data android:name="com.sec.android.multiwindow.MINIMUM_SIZE_H" android:resource="@dimen/app_minimumsize_h" />

I don't know if the last four are necessary, you can test :)

and also search for this lines:

<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
</intent-filter>

And change them to this lines:

<intent-filter>
<action android:name="android.intent.action.MAIN"/>
<category android:name="android.intent.category.LAUNCHER"/>
<category android:name="android.intent.category.MULTIWINDOW_LAUNCHER"/>
</intent-filter>

Save the androidmanifest file.

Step 4​

recompile the app,

Press Shift + empty space inside the folder and then choose open cmd here / open cmd and navigate to this folder using the line "cd C:\Users\....."

in the cmd type "Apktool b yourappname" this will recompile the folder and create a new apk inside the folder, inside folder dist.

Step 5​

signing the app, transfer the apk from "yourappname/dist" to a folder named "signapk" and place all the zip content there.

Press Shift + empty space inside the folder and then choose open cmd here / open cmd and navigate to this folder using the line "cd C:\Users\....."

type inside the cmd:

"cd C:\SignApk

java -jar signapk.jar certificate.pem key.pk8 your-app.apk your-app-signed.apk

Example - java -jar signapk.jar certificate.pem key.pk8 D:\Users\xxx\Desktop\signapk\yourappname.apk D:\Users\xxx\Desktop\signapk\yourappname-signed.apk"

this will create a new apk file called yourappname-signed.apk which can be installed and should support multiwindow feature.

Guys this is my first guide,mod edit, my first everything, consider this :) thx xda , also thx to [MENTION=4443356]v6ser[/MENTION] :P

NON GALAXY S6 USERS, Please Test AND UPDATE :P