Think of an Android expert. Why do you consider this person an expert? “She knows a lot about Android”, you say. But how do you know? You know because she shares her knowledge, through blogs, talks, StackOverflow etc.
Experts are just that, people who share their knowledge. Sharing puts you in a positive feedback loop: the more you share, the more knowledgeable you become. Let me walk you through some concrete steps you can take to start sharing and build up your expertise.