restoring state in a presenter with MVP

https://medium.com/@cervonefrancesco/model-view-presenter-android-guidelines-94970b430ddf says to restore state in the model instead of the presenter. What if I have a very simple "model", say a binary toggle that updates a textview to be on or off? Creating a model Toggle class that has a single string value seems like overkill.

Another option is to pass the bundle from my Activity into a corresponding method in my presenter inside onSaveInstanceState and restore it similarly with onCreate. But the article also says that we should avoid having android dependencies in the presenter.

Finally I tried using Icepick but this did not work:

MainActivity.java

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Icepick.restoreInstanceState(this, savedInstanceState);
(Button) findViewById(R.id.btn).setOnClickListener(this);
presenter.onCreate();
}

@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
Icepick.saveInstanceState(this, outState);
}

@Override
public void onClick(View view) {
presenter.onButtonClicked();
}

@Override
public void updateState(String state) {
tv.setText(state);
}


MainPresenter.java

public class MainPresenter {

private MainView mainView;
@State String toggle;

@Inject
public MainPresenter(MainView mainView) {
this.mainView = mainView;
}

void onCreate() {
mainView.updateState(toggle);
}

void onButtonClicked() {
mainView.updateState(toggle.equals("on") ? "off" : "on");
}
}


What are my options? If I have to use the model approach can I see an example of this for my case?

1 Answer
1

If you're using annotation processing to maintain the state, it won't automatically populate data into your presenter without Icepick.saveInstanceState(this, outState) which you can't call in the presenter.

Icepick.saveInstanceState(this, outState)

@State String toggle;

@State String toggle;

This line should be present in the activity. Have a method in your presenter to request data by toggle. Something like this:

@State String toggle = "off"; //default value

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
Icepick.restoreInstanceState(this, savedInstanceState);
(Button) findViewById(R.id.btn).setOnClickListener(this);
presenter.onCreate();
presenter.setState(toggle)
}


You can store this value as the global variable in the presenter and decide the app flow accordingly.

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