Learning How to Prototyping

Yesterday i learn, about making dynamic layout on android and i found new lesson. Making user interface(UI) directly on android without making some sketch is exhausting due there many ideas to add this and remove that so there are no certainity about UI i want to build and long time to show how it look like on phone. I found there something missing and development like this is too time consuming,I goes learn deeper about UI designing, and found new method missing on my workflow : Prototyping, User Flow Design, and lead me to learn about UX.