Question

I would like to create one class which holds some key values of the app so I can share and access them in all activities. This is how I have done it so far:

I define a class like this:

public class GlobalVars {
    public static String str1;
    public static String str2;
    public static Integer int1;
    public static Integer int2;

    public static MyDBAdapter myDBAdapter;

    public static Boolean isOK1() {
        return str1.length() > 3;
    }
}

This is how I fill them at the start of the app:

private void getAllInfo() {

        // first get the info
        Cursor appCursor = cursor;

        GlobalVars.str1 = appCursor.getString(appCursor
                .getColumnIndexOrThrow(MyDBAdapter.KEY1));
        if (GlobalVars.str1 != null) {
        } else {
            GlobalVars.str1 = "";
        }

        GlobalVars.int1 = appCursor.getInt(appCursor
                .getColumnIndexOrThrow(MyDBAdapter.KEY_NUMBER1));
        if (GlobalVars.int1 != null) {
        } else {
            GlobalVars.int1 = 1;
        }

and I access those values normally just by writing

GlobalVars.int1 = ...

or

i = GlobalVars.int1;

wherever I need to

At the very end when the app finishes I put all the values back in the DB.

Is this the best way to handle global variables in this way?

I get really strange NullPointerException Errors when accessing the GlobalVars.int1 variable with users who got the app – while I am 100% the value is always correctly assigned and never with a null.

Do I have to allocate the GlobalVars object before using it?
Is there any possible explanation how those values can become null without me assigning null anywhere?

Thanks

Answer 1

I would recommend to use shared preferences for configuration / shared data storage ( as long as you have reasonable amount of them – database is for potentially unlimited amount )

I work on dependency injector for preferences ( setting values from preferences works already ):
https://github.com/ko5tik/andject

As for your question about null value – if you not assign it, it is null