I have a form in android mobile app which has 3 nested autocomplete each one will depends on the previous one for its value. But the customer wants something better than autocomplete. Since there are lots of items in each field and they don't have any logical order, I've no idea what to do. Any Ideas?
Without really knowing more about the specific use-case, consider your data.
Good UX is all about providing the clearest and simplest way to get the minimum data required to do the job to the user's specifications.
You said in your comment that you've got Color Family, Color Code and Packaging and this is a loop you'll need to run through quickly for multiple products in the same order.
A brief googling (because of my own lack of familiarity with the terms Family and Code in this context) cleaned it up in my head and explained why Color code is causing you problems.
Your ideal case I believe is to have the colours visible on-screen to select, with Secondary data like the name and color code visible as well.
Benjamin Moore has a good example of what I'm thinking of.
You simply select the family you want from a grid, then you're presented with a sub-grid of the different colours with the codes associated with them, select it and you see more data like the name and ultimately an option to purchase, where you get the price and volume/packaging option.
It's a simple visible hierarchy and it doesn't use drop-downs or autocomplete anywhere. You can also readily adapt it to whatever format you may like. for example a colour-wheel instead of the initial Family Grid.