title: R.java file in Android Studio
body: <p>I'm doing my first projects with Android Studio and I've found that I get an error with the R.java file, because in every class when I make a reference to R.id.X it turns red and it says that it cannot resolve the symbol R..does anyone can help me with this?</p>
  
  <p><img src="https://i.stack.imgur.com/WsHlH.png" alt="enter image description here"></p>