I am new to Android development. Here comes a question to me, what is the difference between tutorial 12 and tutorial 13+14. "

According to tutorial 12, i can simply drag those button and text in the design view of my main activity.xml

However, Bucky did the same thing by adding code in the main activity.java  in tutorial 13+14

1.Whats the difference between these two methods?
2. If i do method 1 , do i need to amend code in java file?
3. Which tutorial should i watch if i wanna create something after i press the button created in launcher ( my first screen . xml)

Thank you very much.