Please follow below steps to get source file:
Step 1. Rename the .apk file to .zip file.
Step 2. Download dex2jar and extract that zip file to another folder.
Step 3. Now open command prompt and go to the folder created in previous step and type the command "dex2jar classes.dex"
and press enter.This will generate "classes.dex.dex2jar" file in the same folder.
Step 4. Now Download java decompiler from the link and extract it and start(double click) jd-gui.exe
From jd-gui window browse the generated "classes.dex.dex2jar" file in demofolder, this will give all the class files by src name. Now from the File menu select "save all sources" this will generate a zip file named "classes_dex2jar.src.zip" consisting of all packages and java files.
Step 5. Extract that zip file (classes_dex2jar.src.zip) and you will get all java files of the application.
Above steps will generate java files but to get xml files perform following steps.
Step 1:Getting xml files from apk
Step 2. Download apktool and apktool install from the link and extract both files and place it in the same folder (for example "demoxmlfolder").
Place the .apk file in same folder (i.e demoxmlfolder)
Step 3. Now open command prompt and goto the directory where apktool is stored (here "demoxmlfolder") and type the command "apktool if framework-res.apk"
Above command should result in "Framework installed ..."
Now in command prompt type the command "apktool d filename.apk" (where filename is name of apk file)
This will generate a folder of name file name in current directory (here demoxmlfolder) where all xml files would be stored in res\layout folder.