Prefixing string resource identifier to select alternate version at run time

Issue

Normally, I fetch a string value from a resource XML using:

String mystring = getResources().getString(R.string.mystring);

Now, I would like to select an alternate version of the string based on some runtime condition.

String selectivestring;
if (someBooleanCondition)
  selectivestring= getResources().getString(R.string.mystring);
else 
  selectivestring= getResources().getString(R.string.theirstring);

So far so good, but since I have many such "alternative string pairs", I would like to methodically prefix one type (say, "my_") and the alternate type (say, "alt_"):

String selectivestring1;
if (someBooleanCondition)
  selectivestring1= getResources().getString(R.string.my_string1);
else 
  selectivestring1= getResources().getString(R.string.alt_string1);
.
.
.
String selectivestring2;
if (someBooleanCondition)
  selectivestring2= getResources().getString(R.string.my_string2);
else 
  selectivestring2= getResources().getString(R.string.alt_string2);

(The above code is for illustration only. What I eventually want to do is to parametrize this so that I can put this in a loop, array or own accessor)

If there were a preprocessor in Java, I could have just used string concatenation to select "my_" vs. "alt_" prefix. But since I know there isn't, is there a way, workaround or suggestion to modify the string resource identifier at runtime, as outlined above?

Note: The alternate version of each string is not in a different language/locale. I am basically trying to keep the original and the alternate versions of the string together, next to each other, in the same resource file, so that I can easily compare the two.

Solution

Firstly, your code could be a bit better like this:

int resource = 
   someBooleanCondition ? 
       R.string.my_string2 : R.string.alt_string2;
String selectivestring2 = getResources().getString(resource);

As you described, that could be done with reflection, here is a very simple example:

package br;
import java.lang.reflect.Field;

final class R {
    public static final class string {
        public static final int alt_string1=0x7f060601;
        public static final int alt_string2=0x7f060101;
    }
}
public class StaticReflection {

    public static boolean globalVariable = false;

    //this would be android method getString
    public static String fakeGetString(int id){
        switch (id){
        case R.string.alt_string1: return "it";
        case R.string.alt_string2: return "works";
        default:
            return "O NOES";
        }
    }

    //static method
    public static String getResource(String resId) throws Exception {
        if (globalVariable){
            resId += "string1";
        } else {
            resId += "string2";
        }
        Field f = R.string.class.getDeclaredField(resId);
        Integer id = (Integer) f.get(null);
        return fakeGetString(id);
    }

    public static void main(String[] args) throws Exception {
        globalVariable=true;
        System.out.println(getResource("alt_"));
        globalVariable=false;
        System.out.println(getResource("alt_"));
    }
}

Answered By - mrcaramori