Before answering this very general question, answer a few leading ones, and at the same time - more important ones.
Do you have any programming knowledge? If so, how well do you understand Java? If the answer to both of these questions is yes, then you don't have to wait long to get into Android Developers. If the answer is no, then you need to start by learning the basics of programming. CodeGym is at your service.
Do you have any backend and database knowledge? The backend for a messaging application can be relatively simple or very complex, depending on the nature of the messages. Can they be sent to a group of users or only person to person? Can I edit, update, delete messages? Can I mark them as spam? Imagine what else you would like to see.
Are you familiar with graphic design/UX? Building an app isn't just about writing code. If you're building an app as an internal tool or just for fun, this question may not be that important to you. However, if you plan to make money on this application, then this is extremely important! The competition is huge: there are over 700,000 apps on the Play Market, and yours should be at least user-friendly, and even better, aesthetically appealing. Otherwise it will be very difficult to break into the top.
Scott Lieberman, co-founder and CTO of TapFit: “I was well versed in Ruby on Rails, PHP, and PostgreSQL when I decided I wanted to build my first application from scratch. I would say that it took me two months to understand mobile programming and six months to become a decent mobile developer. You should think carefully about how and what will work on mobile devices in terms of functionality, interaction, speed and memory. Therefore, I would say that depending on the answers to three important questions, the creation of such an application will take you from two months to a year.
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