Here i have called URL first then only declared mTitle value.thats why i have faced problem here.
Now i got the solution:
I have declared mTitle first afterthat only have called URL like below.
mTitle = b.getString(KEY_SUBCATE);
URL = "http://api1.sfsfsffsf.com/dev/categories/?fields=&categoryid=" + mTitle + "&access_token=bfb787a";
solved xml parsing listview in android like category,subcategory