How do I use sharedPreferences outside of an Activ

问题:

I've been stuck on this very simple problem for hours now and Ive been unable to find any suitable solutions through google.

I am trying to use the SharedPreferences class in the model layer of my application. Specifically I want to be able to save or fetch the user name and the corresponding token whenever the application is started(if the user sets the application up for auto login that is).

Is there a way for me to use SharedPreferences for this issue or am I forced into using FileInput/Output ?

回答1:

Where do you instantiate your Model class?

Just pass either a context or the SharedPreferences to the constructor:

public class Model {
    private final Context context;
    private final SharedPreferences sharedPrefs;

    public Model(Context context) {
        this.context = context;
        sharedPrefs = context.getSharedPreferences("name", 0);
    }

    private String doSomething(){
        return sharedPrefs.getString("key", "defValue");
    }
}

回答2:

SharedPreferences isn't called only from Activity, but from Context (which Activity extends) so you can use the application context as well.

回答3:

You can use SharedPrederences from any code that holds a Context. From the Activity documentation at http://developer.android.com/reference/android/app/Activity.html:

Activity persistent state is managed with the method getPreferences(int), allowing you to retrieve and modify a set of name/value pairs associated with the activity. To use preferences that are shared across multiple application components (activities, receivers, services, providers), you can use the underlying Context.getSharedPreferences() method to retrieve a preferences object stored under a specific name. (Note that it is not possible to share settings data across application packages -- for that you will need a content provider.)