It is a file for setting the operation, such as processing when pressing the button. For those who have experience developing with JavaScript, it may be easier to understand as html files in JavaScript development. It is a file for setting appearance, such as the position of buttons and text boxes. In development using Android Studio, we will implement it by editing the xml file and the java file. Basically, as with the image above, the menu other than the necessary minimum (code and preview) is closed. You can open and close the menu from the bottom and the left and right bars. It is familiar to those who have used the integrated development environment, except that there is a preview screen on the right side.
I will show you how to develop Android application using Android Studio.