Get Lock screen Wallpaper android

Question

I want to get the current wallpaper drawables of both lockScreen & homescreen but i can't figure out how to get LockScreen Wallpaper.

I have used this Code to get HomeScreen Wallpaper Drawable & its Working Fine

WallpaperManager wallpaperManager = WallpaperManager.getInstance(this);
Drawable wallpaperDrawable = wallpaperManager.getDrawable();

And for LockScreen drawable,

WallpaperManager wallpaperManager = WallpaperManager.getInstance(this);
Drawable wallpaperDrawable = wallpaperManager.getBuiltInDrawable(WallpaperManager.FLAG_LOCK)

this Returns Null Drawable Value...

Is there any other way to get Current LockScreen Wallpaper !