Question

In android, I’m not sure I quite understand the R class. I’m going through the sudoku example, and I have this snippet of code:

switch (v.getId()) // the id of the argument passed is evaluated by switch statement
{
    case R.id.about_button: // 
    Intent i = new Intent(this, about.class);
    startActivity(i);
    break;
    // More buttons go here (if any) ...
}

I’m brand new to Java, but from what I gather it looks like it’s taking input (the touch screen being touched on the button) and evaluating the argument. Then the case statement is setup if the about button is recognized, and a new interface screen is created and then navigated to on the phone.

Is this right?

If I got the gist of that correct, why is the deal with the “R” class?

Why is it called to recognize the ID of the button?

I thought the super class (in this project) was the SudokuActivity class.

Answer 1

R.java is the dynamically generated class, created during build process to dynamically identify all assets (from strings to android widgets to layouts), for usage in java classes in Android app. Note this R.java is Android specific (though you may be able to duplicate it for other platforms, its very convenient), so it doesn’t have much to do with Java language constructs. Take a look here, for more details.