android - How to use getString() on static String before onCreate()?

Question

I am trying to use getString() to get an String from resources to assign it to an String array before my activity is created:

private static final String[] MenuNames = {
    Resources.getSystem().getString(R.string.LCMeterMenu),
    Resources.getSystem().getString(R.string.FrecMenu),
    Resources.getSystem().getString(R.string.LogicAnalyzerMenu),
    "Prueba con achartengine",
    Resources.getSystem().getString(R.string.BrazoMenu)
};

When I use Resources.getSystem().getString(R.string.LCMeterMenu), Eclipse doesn't complain but I get an error at runtime:

Caused by: android.content.res.Resources$NotFoundException: String Resource ID #0x7f0a000a

But if I put inside onCreate():

Log.i("StringR", "String: " + getString(R.string.LCMeterMenu));

I get the String but I can't assign it to the final String I defined before. If I use only getString() before onCreate() I get and static error message. How can I use resources before onCreate() for global variables?

Answer 1

You cannot initialize a static final field from resources; the field needs to be initialized at the time the class is initialized and that happens before the application resources have been bound at run time. (By the way, the reason you cannot use Resources.getSystem() is that the Resources object you obtain that way contains only system resources, not any application resources.)

If you need those strings available before the application resources are bound, the only practical thing to do is to put the strings into the code directly. However, the "Android way" would be to organize your code so initialization only needs to happen during (or after) onCreate(). Just initialize the string array in onCreate() and don't worry about making the fields static or final.

If you don't want the string array to be associated with a particular activity, then you can subclass Application and read the array from resources inside the application class's onCreate() method. (You also need to declare your custom application class in the manifest.) However, the docs recommend against such an approach. (Since the array is private, I suspect that it is closely tied to a single activity anyway, so the use of an Application subclass doesn't seem warranted.)

An alternative is to declare a singleton class for your array. The singleton accessor function then needs a Context so it can retrieve the resources if necessary:

public class StringArray {
    private static String[] theArray;
    public static String[] getArray(Context context) {
        if (theArray == null) {
            theArray = context.getResources().getStringArray(R.array.my_strings);
        }
        return theArray;
    }
}

(This assumes the string data are defined in a <string-array> resource like @JaiSoni suggested in his answer.) Once again, the member field cannot be declared final.