I successfully retrieved the selected wallpaper from wallpaper manager and applied it to my app background with this code:
`
LinearLayout parent = (LinearLayout) findViewById(R.id.linearLayoutParent);
final WallpaperManager wallpaperManager = WallpaperManager.getInstance(this);
final Drawable wallpaperDrawable = wallpaperManager.getDrawable();
parent.setBackgroundDrawable(wallpaperDrawable);
`
But this code doesn't work if the selected wallpaper is a live wallpaper, i just searched for a solution in google and didn't find any.