Android MVP：在Presenter中访问内容提供商

Question

I am working on a project with Android MVP, so far the things I am able to understand as thumb rules for this architecture are:

1. Presenter should not contain any android code.

2. View should not contain a reference to the Model.

I am following this and so far I am successful in implementing this. In my project, I need to access ContentProvider and SharedPreference. For them, I need context to be passed to the presenter and this is bad practice.

One solution is to create a class for accessing the SharedPreference and let it implement the interface whose reference could be passed to the presenter.

1. Is this a standard way to do this?
2. How should I implement the content provider part?

Am I missing something with this architecture implementation?

Answer 1

This is for those who come across this problem.

In my question as I quoted -"I create a class for accessing the SharedPreference and let it implement the interface whose reference could be passed to the presenter."

I asked about this solution from Antonio Leive who has written a great article on Android MVP, here is the link http://antonioleiva.com/mvp-android/ .

Here is his reply:

"The thing you mention is related to dependency inversion. You must delegate the use of the framework to the minimum possible part of the code.

So, for instance, if you want to use the SharedPreferences on a presenter, you will use an entity called PreferencesManager (or something more descriptive) that will probably be just an interface. You then inject (through the constructor or a setter) an implementation of the interface, which will use the context to retrieve the preferences. You can do the injection manually, which will become a bit tedious if you have many entities that use the context, or use a dependency injector. Do you know Dagger? I have three articles about it in the blog. Though they're based on Dagger 1, the theory may help you understand the concept."

This is how I implemented,

 interface AppPrefsManager {
    <T> void  putData(String key,T obj);
    <T> T getData(String key, T obj);
}

Create the implementation of the above interface,

  public class AppPrefs implements Repository.Appprefsrepository {

private Context context;

private static AppPrefs ourInstance;
private SharedPreferences preferences;

public static AppPrefs getInstance(Context context) {
    if (ourInstance == null) {
        ourInstance = new AppPrefs(context);
    }
    return ourInstance;
}

private AppPrefs(Context context) {
    this.context = context;
}

public SharedPreferences getPreferences() {
    if (preferences == null) {
        preferences = context.getSharedPreferences("prefs", Context.MODE_MULTI_PROCESS);
    }
    return preferences;
}

public <T> void putData(String key, T obj) {

    SharedPreferences.Editor editor = getPreferences().edit();
    if (obj instanceof String) {
        editor.putString(key, (String) obj);
    } else if (obj instanceof Boolean) {
        editor.putBoolean(key, ((Boolean) obj).booleanValue());
    } else if (obj instanceof Integer) {
        editor.putInt(key, ((Integer) obj).intValue());
    } else if (obj instanceof Long) {
        editor.putLong(key, ((Long) obj).longValue());
    }
    editor.commit();
}




public <T> T getData(String key, T obj) {
    if (obj instanceof String) {
        return (T) getPreferences().getString(key, (String) obj);
    } else if (obj instanceof Boolean) {
        return (T) (Boolean) getPreferences().getBoolean(key, ((Boolean) obj).booleanValue());
    } else if (obj instanceof Integer) {
        return (T) (Integer) getPreferences().getInt(key, ((Integer) obj).intValue());
    } else if (obj instanceof Long) {
        return (T) (Long) getPreferences().getLong(key, ((Long) obj).longValue());
    }
    return null;
}
 }

Pass the implementation of interface to the presenter, I initialized the presenter as

AppPrefsManager appprefs=AppPrefs.getInstance(this);
Presentor mypresenter=new Presenter(apprefs);

Now my Presenter can access the SharedPreferences.