Question

I would like to know why we use XML for the creating user interface layouts in Android. I know that it decouples the business logic from the design but what is the significance of the XML other than that?

Also I would like to know the significance of the auto-generated R.java file in this. All I know that it is generated according to the changes in the resources and that it helps us to access the widgets and resources through their IDs.

It would be great if someone could give a clear idea on these two aspects.

Answer 1

Unlike what everyone said about the XML being easy and efficient. Here is what I read in Hello Android by Ed Brunnette (p. 49) which made sense.

Android is optimized for mobile devices with limited memory and
horsepower, so you may find it strange that it uses XML so
pervasively. After all, XML is a verbose, human-readable format not
known for its brevity or efficiency, right?

Although you see XML when writing your program, the Eclipse plug-in
invokes the Android resource compiler, aapt, to preprocess the XML
into a compressed binary format.**It is this format, not the original
XML text, that is stored on the device.

This was the kind of answer that i was looking for.(sorry if my question meant otherwise).

The reason that XML was chosen is mainly because of its familiarity and the number of IDE tools that natively support it. The developers could have chosen JSON for example and still compiled that to binary.The auto-generated R.java file is a helper for the IDE so that you can get the benefit of autocomplete when you want to access a resource.