Access application context in a storage class in Android

Question

I have an app on Android 4.0. It uses the PreferenceManager class to -- among other things -- let the user specify how many decimal places of a number to show.

mPreferences = PreferenceManager.getDefaultSharedPreferences(this);

Generally I have no problem getting the app context in order to access the Preference Manager. My problem is that I have a class (let's call it Record) that isn't subclassing anything that has the app context; it's just a storage class, but it does have a field "NumDecPlaces". Right now, when I instantiate the class from within my app I just pass in the user's #dec places preference. It would be nice if Record could access the Preference manager directly. I suppose I could always instantiate Record with a pointer to the context from which it was created, but that's a lot to remember ;-)

So right now Record subclasses nothing. Any recommendations on what I can do to it to allow it to see the app context?

Thanks!

Answer 1

You could pass the Context object in the constructor. So whenever you try to use that class it will ask you pass a Context object and then use that to get SharedPreferences

For eg.

public Record(Context context)
{
  mContext = context;

  mPreferences = PreferenceManager.getDefaultSharedPreferences(mContext)
}

Answer 2

You can also extend a class with Application, which will be global to the whole application and you can set the context in that class as a member variable and that context will be global to the whole application

Eg. class A extends Application{......}

Answer 3

You can do @Apoorv's suggestion or you can create another class that specifically stores the application context.

public class ContextResolver {

    private static Context context;

    public static void setContext(Context context) {
        if (context == null) {
            throw new IllegalArgumentException("Context must not be null");
        } else if (context instanceof android.app.Activity) {
            context = androidContext.getApplicationContext();
        } else if (context instanceof android.content.Context) {
            context = androidContext;
        }
    }
    public Context getContext() {
       return context;
    }
}

Now you need to call setContext() in the first activity that will be launched once.

public class MyFirstActivity extends Activity {
    public void onCreate() {
         ContextResolver.setContext(this);
    }
}

Now you can retrieve the Context from any part of your code. So in your Record class you can just do this:

mPreferences = PreferenceManager.getDefaultSharedPreferences(ContextResolver.getContext());